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1. CT 4 gt g 4 The signal path from Texas to the eastern U S is a daylit path The electron de nsity within the ionosphere is therefore at its highest level Signals must therefore be of a higher frequency in order to survive the strong D region absorption which exists everyw here along this path This is the primary reason why the LUF is higher than in the previous exam ples Consider now Figure 8 6 which shows the results of the elevation angle plot for the path from Texas to the eastern U S This interesting plot differs from previous elev ation angle plots presented in that there are two sets of traces one set for F region reflection s and another set corresponding to E region reflections The small set of traces in the lower left labelled 2 hop 3 hop and 4 hop are E layer reflections The highly ionized state of the E region during the day permits reflections from higher frequencies provided the elevation angles are low This figure then tells you that transmissions from Texas to the eastern U S can eith er be accomplished through E region reflections on lower frequencies or F region reflections on hi gh frequencies This information was not clearly evident in Figure 8 5 Let s try to choose a frequency which should have decent signal quality low dis tortion and does not require very narrow antenna radiation patterns to achieve these res ults The bes
2. Figure 4 2 Global Map of MUFs for 3 000 kilometers It is important to understand how to correctly interpret MUF maps To help us in this regard let s examine how to correctly interpret the results of the map in Figure 4 2 Since this map shows the MUF for a distance of 3 000 kilometers each point on the map is t he MIDPOINT of a 3 000 kilometer path For example this map shows that South Africa has an MUF of 9 MHz for a distance of 3 000 kilometers Therefore if the MIDPOINT of your 3 000 km signal path passed over South Africa you could expect to see an MUF of 9 MHz Phrased a little differently the MUF for a transmitter situated 1 500 kilometers the path midpo int away from South Africa would be 9 MHz if the signal passed over South Africa This map wou ld not apply for signals with greater or smaller path distances It only applies for signals that travel 3 000 kilometers in ground distance This is exceptionally useful information and can help you determine optimum freq uencies to use throughout the day for specific paths It can also help you determine how long you can expect MUFs to remain above a specific frequency before MUF failure occurs Noti ce that the smallest maximum frequencies occur during the nighttime and early morning hours while the highest MUFs occur when the Sun is high in the sky near local noon And as was e xplained with the foF2 maps the highest gradients in MUF occur near sunrise near the eq uatorial a
3. Notice how the traces in Figure 8 6 curve back in on themselves near the MUF The lower trace prior to the sudden c urve at the MUF represents the low angle rays Low angle rays are relatively stable and are the most reliable rays to support communications High angle rays are much less stable e xcept near local noon where the electron density does not change significantly and usually are more difficult to sustain communications on The high angle rays are responsible for forming the u pper curves in Figure 8 6 curving from the lower right to the upper left beginning at the MUF or nose of the traces High angle rays can be discerned in almost all of the supported mode s of propagation except perhaps the 4 hop mode and the E region reflections Under some circumsta nces the high angle rays can support propagation on frequencies much higher than the basic MUF If the transmitting antenna radiates most of its power between elevation angles of about 5 to 35 degrees with a primary direction of radiation at about 15 degrees in el evation then our tactics must change In this case the usefulness of the 1 hop mode of propagati on will be limited because most of the power radiated will not fall between the 5 and 8 degree elev ation angle required to reach the receiver from Texas in one hop However some of the radiated power will likely be received at the receiver But the signal from the one hop mode will al most certainly be weak For this reas
4. As the frequency increases a point will be reached where the ionosphere will fail to return a signal This penetration frequency is also known as the critical frequency and represents the maximum frequency that can be ionospherically returned by a vertically propagated signal Figure 2 3 shows two rays being transmitted at an 89 99 degree angle essentially vertical but slightly offset from 90 degrees so we can observe the ray behaviour more clearly The horizontal scale used is two z kilometers in distance The vertical line G down the middle of the figure represents the Figure 2 3 Penetration at the critical frequency 47 0000 P Mag LAT 53 44 Km Deg MHz Sig El 0 Kn ist 0 0 489 9851 Deg Iono Dst 320 4 18 1 kilometer mark In this example the two rays were offset by slightly differen t frequencies using the Sweep Frequency function of PROPLAB The ray which returns to the grou nd uses a frequency of 5 5350 MHz which is very close to the critical frequency of 5 53 52 MHz Since the frequency of the ray is slightly lower than the critical frequency the ionosphere is able to reflect the ray back to the ground The other ray in the figure is trans mitted at the same angle of elevation but offset slightly in frequency to 5 5355 MHz Since this ray is slightly above the critical frequency the ray penetrates
5. The real time maps displayed by PROPLAB can be updated at user defined intervals of minutes For example the grayline can be updated once every minute if desired b y specifying an update rate of 1 minute Specifying an update rate of 0 zero minutes forces PROPLAB to continually update the display as quickly as possible For contoured maps such as maps of maximum usable frequencies the timer starts ticking as soon as the map is finished being drawn If your system requires several minu tes to draw a contoured global map of maximum usable frequencies and you specify an update rat e of 1 minute for these maps PROPLAB will pause for one minute after it has finished drawing the map before it begins working on the computations to draw the next map after the 1 minute interval has expired 11 4 Displaying Local Times for Cities Around the World The local times for cities around the world can be displayed if a file by the name of CITYTIME DAT exists in the same directory as the PROPLAB software This file s hould describe cities geographical locations and time zone information in the same format as the geographical location database file PROPLAB LOC PROPLAB already comes loaded with a few cities in the CITYTIME DAT file whose local times can be displayed in real time as soon as you load up PROPLAB Since the CITYTIME DAT file is in exactly the same format as the main geographic al database file PROPLAB LOC if you want to include other cities
6. and coming into greater usage is the nanotesla nT One gamma is equivalent to one nanotesla The planetary K index values for a given 3 hour interval are obtained by simply computing the numerical mean of all of the K indices for all known stations for each 3 hour interval 2 3 2 The Geomagnetic A Index This index is based on the K index as follows Each K index for every station is associated with a given a index as previously described The A index for a particular station is simply the average of the eight a indices for that UTC day For example eight K indices 9 given as 3445 4332 would correspond to an A index of 23 This is done by compu ting the average of the associated eight a indices as follows 15 27 27 48 27 15 15 7 8 22 6 or 23 This simple method of computing the A indices and the table given above can be applied to most middle latitude regions High latitude stations will be associated with a different range index a one which spans larger ranges The PROPLAB software will accept as input the A index value The A index value s broadcast by radio stations WWV and WWVH on HF frequencies 2 5 5 0 10 15 and 20 MHz at 18 minutes past each hour can be input into the software Alternatively for 3 hour values the K index value given in this same message can be converted into an equivalent A index value as described above and then input into the software This may under rapidly c
7. Auroral activity 9 Auroral Oval Simulator 25 Auroral sporadic E 11 Auroral zone 9 aurora australis 9 auroral absorption 11 Auroral activity processes 9 auroral sporadic E 11 electrons 10 northern lights 9 oval 9 radio propagation 10 signal degradation 10 significance 10 sporadic E 11 Auto SSN Calculation 38 AutoQTH 29 Basic MUF 112 Books ionospheric 1 propagation 1 Bugs 27 C layer 2 CCIR 19 127 INDEX Central meridian 6 Chromosphere 4 5 CME 5 Collision frequency shaping parameters 50 Contours 98 flashing screen box 75 Corona 4 Coronal mass ejections 5 Cosmic Ray layer 2 Critical frequencies 75 foE 18 foFl 18 foF2 18 Critical frequency 68 critical frequency 17 Cutoff latitude 12 D region location 2 Data gaps 52 Defining sporadic E with a mouse 68 without a mouse 69 Defocusing 23 Directional antennas 54 Disappearing filaments 5 DSF 5 Ducting 63 DX 3 E region 2 Effective sunspot number 24 Electron densities 58 Electron density 3 86 111 112 peak 2 Electron density profiles 56 Elevation angle plot 111 Elevation angles 103 Environment 3 Equatorial anomaly 76 Es location 2 EUV 2 128 Evanescent 45 Extreme ultraviolet light 2 F region 2 Fl 2 F2 2 F1 2 F2 2 Filters 115 Flare locations 6 Flares PCA 12 proton flares 12 FoE 79 foF2 minimum 19 FOT 112 125 Gamma 8 Generating maps 25 Geographical locations Defining 29 grid coordinate 29 name entry 29 numerical entry 29 Geoma
8. Rays tha t intersect any portion of these sporadic E regions may be affected by the enhanced ionization in these regions SECTION 6 SIMPLE AREA COVERAGE MAPS Based on the Simple Ray Tracing Technique One of the most impressive features of PROPLAB lies in its ability to produce br oadcast coverage maps also known as area coverage maps Broadcast coverage maps are maps showing the coverage quality or characteristics of signals that are broadcast by radio stations whether amateur or professional PROPLAB combines the results of the simple ra y tracing technique results to produce broadcast coverage maps This section shows you how this is done and how to interpret the results 6 1 How are Broadcast Coverage Maps Constructed A radio transmitter cannot broadcast without some form of radiator The radiator is the antenna and the signal which enters the antenna is radiated outward in a direction that is dependent upon the type of antenna that is used Antennas can be constructed to be exceptionally directional in nature where narrow beams of radio signal energy are broadcast O thers are constructed to broadcast radio energy equally in all directions These are calle d omni directional antennas Before a broadcast coverage map can be generated it is essential to know the approximate radiation pattern of the antenna being used to transmit or receive the signals PROPLAB PRO Version 2 0 uses the currently selected antenna radiation pattern
9. a i Xmit Lat Recv Lat o 05 00 UTC during geomagnetically quiet conditions The frequency separation grid lines shown in Figure 8 1 require further explanat ion Each labelled frequency ex 9 6 MHz is associated with a bright WHITE vertical line which is not discernable in the black and white rendition of this figure At each whole numb ered frequency 8 0 9 0 10 0 11 0 MHz etc a LIGHT GRAY vertical line is plotted For this reason some lines may appear irregularly spaced in the frequency grid for the figures which have been reproduced here However while running PROPLAB they are easily discerned from one another The upper panel of Figure 8 1 describes the estimated signal quality Please note that the given signal quality is not to be taken as an absolute The computed signal qual ity is simply the average signal quality of all rays that arrive at specific frequencies They do not take into consideration effects of strong multipathing ionospheric focusing etc For the se reasons the given signal quality should be used as an estimate only and a guide to the gener al quality of 105 signals that can be expected We will improve the quality computation figures in future releases Figure 8 1 shows that five modes of propagation are possible between Hawaii and Colorado on the high frequency bands 2 hop mode 3 hop mode etc to the 6 hop mode The lower the frequency the more modes that are supported A greater number of
10. it also corresponds to the location wh ere the electron density is a maximum for that region or layer of the ionosphere a a T EEEE The height of maximum electron A Es density for the various layers of interest are PE i 28 denoted hmD for the D layer hmE for Gin Rasiai 10 0849 _ Bes esti 2028 8 the E layer hmF1 for the F1 layer and hmF2 for the F2 layer For long distance communications the F2 layer is usually the 06 00 UTC controlling layer Through simple geometry it can be shown that signals can travel ERER greater distances as the height of maximum electron density increases In Figure 2 4 two rays are traced at different times of the day The first ray is traced at 03 00 UTC Haba 2000 Sooo and uses the same frequency and angle of Figure 2 4 Propagation to greater distances by raising elevation as the second ray traced three the height of maximum electron density hours later at 06 00 UTC During this 3 19 hour period of time the height of maximum electron density in the F2 region inc reases by approximately 50 km This allows the signal to travel almost 1 000 kilometers farther This is one reason why propagation improves after sunset The electron density in the lower regions disappears which permits easier access to the F2 region which is still strongly ionized and capable of reflecting higher frequency signals over long distances One of t he disadvantages of night sector propagation is the reduction in cr
11. our magnetic field generates a great deal of energy which is to some extent st ored by the magnetic field of the Earth Occasionally this energy is suddenly released The resulting disturbance is known as a geomagnetic substorm A geomagnetic storm is made up o f many substorms and can have a serious impact on the ionosphere Geomagnetic storms are almost always associated with decreases in electron densi ty in the F region which results in a lowering of the maximum usable frequency This decreases the usable bandwidth and can cause difficulties in communicating over long distances We will discuss this in greater detail later 2 2 Solar Terrestrial Relationships The Sun is an integral part of our environment We depend on it for life sustain ing light energy and heat It is essential that we have a basic understanding of how the Sun can influence the ionosphere before we can expect to understand the behaviour and ch aracter of the ionosphere This section is devoted to explaining how the sun interacts with our terrestrial environment and particularly the ionospheric environment 2 2 1 General Features of the Sun The Sun lies at an average distance of 149 600 000 kilometers or 93 500 000 mil es from the Earth The Sun is about 330 000 times more massive than the Earth and the Moon combined It has a photospheric temperature of about 5800 degrees Kelvin and a gravitational pull over 333 000 times stronger than here on Earth The average r
12. 52 PROPLAB first shows you the current 3 D data settings This is followed by the b earing from the transmitter to the receiver as well as the computed great circle distan ce between these two points Check to make sure it is all correct If it is not use Main Menu Op tion 8 or 3 to change the geographical locations of the transmitter and receiver to the correct latitudes and longitudes Then re enter this section to specify the three dimensional data PROPLAB first asks you to specify how many degrees adjacent perpendicular to t he bearing of the great circle path ionospheric profiles should be constructed F or example if you specify 10 degrees here PROPLAB will construct ionosphere profiles spanning 10 degrees on BOTH sides of the main great circle bearing It will therefore construct profiles covering a total azimuthal span of 20 degrees 10 degrees per side A value of 1 degree will cau se PROPLAB to construct profiles only one degree on either side of the main bearing If the main bearing was therefore 315 degrees from the transmitter to the receiver PROPLAB would constr uct ionospheric profiles at bearings of 314 315 and 316 degrees one degree on each side of the main bearing PROPLAB next asks you how many profiles you want to build along the bearing rang e The bearing range refers to the total azimuthal span for which profiles will be constructed In the first example above the bearing range would have been 20 degrees 10 deg
13. PROPLAB PRO Version 2 0 lets you change any of these colors to any ratio of RGB Red Green Blue values It is therefore possible to change any of the colors used by PROPLAB s graphics plots to any shade or color desired For examp le an RGB combination of 0 0 0 Red 0 Green 0 Blue 0 results in the color BLACK since all three primary colors have an intensity of 0 or dark The maximum RGB value that can be input is 63 which represents a brilliant intensity For example an RGB value of 0 63 0 will produce the brightest GREEN color possible A value of 0 32 0 will produce a GRE EN color that is half as bright as the previous example This will appear on screen as a darker colored GREEN PROPLAB PRO asks you if you want to reset the RGB colors to their default values If you have experimented with the RGB colors and need to reset the colors back to their originals respond affirmatively to this prompt which is only asked if you exec ute PROPLAB using the PROPLAB SETCOLORS command at the DOS prompt To change the graphics color BLACK which is also the background color to WHITE so all graphics are drawn with a white background and black lettering change the RGB values for the color BLACK from 0 0 0 to 63 63 63 Similarly change the RGB val ues for the color WHITE from 63 63 63 to 0 0 0 To make the color RED a dark green you might 27 change the RGB values for the color RED from 63 0 0 to 0 25 0 Almost any other color can be created b
14. at the giv en frequency and sweeping elevation angles around the required angle given This is what was done to produce the results given in Figure 2 5 More accurate results can be obtaine d if you ray trace signals by sweeping the elevation angles using the three dimensional comprehensi ve ray tracing technique You may be surprised how different the signals behave when effects of the Earth s magnetic field and ionospheric tilts are considered PROPLAB also gives you the option of rigorously computing the FOT or Frequency of Optimum Transmission Normally the FOT is considered to be 85 of the MUF 0 85 x MUP Our definition of the rigorously computed FOT differs Our definition requires t hat at least 85 of the radiated transmitter energy is reflected by the ionosphere The remaining 15 is lost to space because of ionospheric penetration In most cases the rigorously computed FOT will be lower than the MUF But in many situations you may see rigorously computed FOTs that actually exceed the MUF For example the MUF may be computed at 23 MHz while t he rigorously computed FOT is computed at 26 MHz This simply tells you that the io nosphere will reflect 85 of the power at 26 MHz It is essentially independent of the MUF 3 4 3 Setting up Regions of Sporadic E Since the comprehensive ray tracing technique does not take sporadic E into cons ideration this section only applies to the simple ray tracing technique The third option of the mai
15. available q uality descriptions are as follows VGOOD Very Good Quality VG G Very Good to Good GOOD Good Signal Quality G F Good to Fair Signal Quality FAIR Fair Quality F P Fair to Poor Signal Quality POOR Poor Quality P VP Poor to Very Poor BLKOUT Radio Blackout No Signal Using these tools of the ray tracing screen it is easy to determine signal qual ity levels as the ray is being traced from one point to another If a ray is degraded to the point where the signal is blacked out a large cross is stamped on the screen at the precise location where the ray completely deteriorates and radio blackout conditions are experienced It is therefore easy to determine exactly where a si gnal dies in the ionosphere There may be some instances where a signal cannot be completely traced through t he ionosphere For example PROPLAB will abort tracing a signal through the ionosph ere if the signal becomes engulfed in an area where the plasma frequency exceeds the operat ional frequency of the signal This can occur for example during transmissions that experience long hops through the ionosphere from a region of darkness into a region of light such as might occur during a darkness to sunrise transition If the signal becomes trapped between the F region and the E region ie within the E layer valley region an indefinite number of hops will occur between these two regions until the electron density either decreases and pe
16. control points are carefully chosen and a respectable amount of time is cons umed simply searching for these control points The MUF for each of these control points is then computed The lower of the two MUF s for the two control points is the MUF for the desired distance This method of computing MUF s is valid and accurate for a wide range of conditions and paths During the MUF computations PROPLAB uses a realistic ionospheric electron densi ty profile for each control point and traces appropriate rays through these profile s until the MUF is found When PROPLAB numerically traces through the ionosphere for these contr ol points 67 it does so using steps in distance that are approximately 2 5 times larger than those that are associated with the Ray Tracing Speed see Section 3 3 3 This significantly speeds up calculations but may degrade the accuracy of the results slightly To increase the accuracy of the MUF computations decrease the ray tracing speed by decreasing the Ray Trac ing Speed value in the Options Menu Section 3 3 3 After PROPLAB has found the MUF the frequency is displayed along with the transmission elevation angle required Using the computed frequency and a direct ional antenna oriented at the appropriate azimuth and the required angle of elevation you sho uld be able to transmit at the maximum usable frequency to the desired receiver location You can verify the computed MUF by ray tracing through the ionosphere
17. correspond to altitude above ground again in kilometers The bottom panel shows the rays which correspond to transmission elevation angles of 0 5 10 15 and 20 degrees above the horizon The upper central pane 1 with the logarithmic scale shows the electron density of each of these rays as they pass through the ionosphere The upper central panel vertical tick marks denote the same distance scale as shown in the large lower panel The electron density trace farthest from the ori gin in the upper central panel therefore corresponds to the ray with the zero degree eleva tion angle in the lower panel In this example the ray with lowest angle of transmission zer o degrees penetrates into the ionosphere where the electron density begins to increase As the density 17 increases the ray begins to show signs of being refracted When the ray reaches a height of approximately 200 km the electron density begins to increase more rapidly along with a corresponding increase in the refractive index This causes the ray to bend more rapidly until a point is reached where reflection occurs The ray then begins a downward desce nt As the ray begins to descend the electron density decreases which causes the ray to be gin refracting again only this time in a direction toward the ground As the ray falls further the level of refraction decreases until the ray finally penetrates the lower boundary of the ionosphere At that point the ray simply travels a
18. elevation angles of arrival For example to include rays which have angles of arrival between 7 and 30 degrees you would specify an upper limit of 30 degrees and a lower limit of 7 Rays less than 7 degrees or more than 30 degrees will be excluded from the analysis Similar filters exist for rays with differing azimuths frequencies signal strengths and ground ranges By specifying upper or lower limits on any of these filters you can very selectively target sections of the ray traced database for inclusion in the anal ysis 9 5 Other Map and Contouring Options The remaining prompts presented by PROPLAB are identical to those prompts given when constructing Global Ionospheric Maps Consult that section of this manual for mo re information regarding these prompts A few side notes are required with regards to the selection of the minimum conto ur to use When generating signal strength maps or maps of minimum elevation angles and po ssible other types of contoured maps PROPLAB usually uses a minimum contour value of zero This lets you determine where along the signal path signal strengths are zero or greater etc If the default of zero is used PROPLAB may while drawing the contours plot small regions out side of the main zero contour that also contain zero contour levels In other words there m ay be satellite or island regions of contours labelled as zero These small isolated island regions are a result of the pre and post processing t
19. for ms the lateral deviation wall and shows you the extent to which rays may be deviated laterally away from the great circle path The great circle path itself is indicated by the line connec ting the transmitter to the receiver This line also forms the 0 zero kilometer lateral deviation ine on the right side of the box the lateral deviation wall The traced lines curving along the base of the grid 64 indicates the true path the signals take through the ionosphere In this case it is obvious the traced rays are being deviated away from the great circle path by ionospheric ti lts and interactions with the Earths magnetic field All distances on the three dimensional grid are labelled in kilometers The dist ance toward the receiver is indicated by the multiple fairly closely spaced lines t hat travel along the base of the grid toward the receiver but perpendicular to the great circle line These lines are then mirrored up onto the altitude wall so it is easier to determine the distanc e of traced rays by examining the altitude of the ray in conjunction with the distance The lateral deviation distances are displayed beside the lines which lie parallel to the great circle line on the base grid These lines like the zero kilometer lateral deviation line which forms the great circ le are mirrored onto the lateral deviation wall so that rays which diverge from the great circle path can be more easily discerned and measured in distance from
20. function to operate properly a Plate Carree map must exist in your map library If one does not exist create one using the MAKEMAP utility If you have more th an one Plate Carree map in your map library file you can select any of them to use here 11 1 Setting the Gray Angle The Gray Angle differs from the grayline in the following way The grayline defines the regions of the world where the Sun is exactly zero degrees in elevation that is it is exactly on the horizon and is either rising or setting The gray angle on the other hand defines the regions of the world where the Sun is a user specified number of degrees in elevation above or below the horizon For example to identify the regions of the world where the Sun is 20 degrees be low the horizon which by the way identifies the ending of astronomical twilight you would enter a gray angle of 20 degrees Positive values correspond to elevation angles of the Sun that are above the horizon Negative values refer to locations where the Sun is below the horizon PROPLAB will plot the gray angles corresponding to elevation angles between 60 degrees and 60 degrees A gray angle value of zero degrees coincides with the grayline 11 2 Real Time Global Ionospheric Maps Perhaps the most powerful feature of PROPLAB s real time mapping system is its a bility to produce real time global maps of ionospheric characteristics PROPLAB will pr oduce real time maps of any of the mappable iono
21. in terms of the azimuthal angle from 0 degrees true north to 360 degre es where 90 degrees points due east etc 119 You can save this graphical screen containing the antenna radiation pattern to a GIF or PostScript file by pressing the G or P keys respectively You can print out the radiation pattern to your printer by pressing the H key Any other key returns you to the Main Menu of PROPLAB All future ray tracing operations whether performed using the simple or compreh ensive techniques will reference the newly selected antenna 10 3 Creating Your Own Antenna Radiation Patterns or Modifying Deleting Existing Patterns All of the antenna radiation patterns used by PROPLAB are stored in the subdirec tory ANTENNAS Using a text editor you can view or modify the contents of any of these radiation patterns To delete an existing radiation pattern so that PROPLAB can no longer use it simply delete the required antenna radiation pattern file from the ANTENNAS subdirector y To create your own radiation pattern copy the template file BLANK DAT to another file of your choosing remembering to keep the name of your new file uniquely different from the existing files so you don t accidentally overwrite an existing antenna radiation pattern For example to create a radiation pattern describing the characteristics of a short wire antenna we could copy the antenna template file BLANK DAT to a new file named SHRTWIRE DAT Notic
22. include effects of the Earth s magnetic field and electron collisions with neutral particles It will also optionally trace signals through a realistic three dimen sional ionosphere However in order to keep the program which is responsible for these sophisticat ed functions within the memory constraints imposed by the DOS environment the rays must be t raced through an undisturbed geomagnetic field Therefore the geomagnetic A index is not used in the complex ray tracing technique However the effects of geomagnetic activity can be approximated by inputting an effective sunspot number that is correlated with solar activity and geomagnetic activity Similarly due to memory constraints the complex ray tra cing method cannot include effects of the auroral zones These are the two most impor tant parameters which the complex method does not include in its computations However the increased accuracy obtained by using the complex method outweighs the influence of the auroral zones and geomagnetic activity Using the complex method the influence of ionospheric tilts chordal hop propagation ducting and much more can be accurately displayed on screen These effects are global in nature and affect all signals travelling everywhere unlike the effects of geomagnetic and auroral activity which tend to be localize d more to the high and polar latitude regions Throughout this manual references will be made to the simple or complex techniques Many of the a
23. long asyou are in the real time mapping system program As soon as you return to PROPLAB s Main Menu r to DOS the original transmitter and receiver locations are restored Two remaining commands that can be used while viewing the maps are the plus and minus keys The plus key causes PROPLAB to increase the geomagnetic A inde x by one point The minus key causes PROPLAB to decrease the geomagnetic A index by one c ount This feature lets you adjust the ionospheric maps that may be dependent on geoma gnetic activity which applies to most of the maps except the geomagnetic ones It is therefore possible to be running PROPLAB in the real time mode and continuously adjusting the A index eve ry three hours when new geomagnetic activity values are broadcast by radio stations WWV or WWVH at 18 minutes past each hour on 2 5 5 10 15 and 20 MHz Incrementing the A i ndex values will also affect the location of the auroral zones which will migrate southward and expand in size with larger geomagnetic A indices With these commands at your disposal it should be easy to see how useful the sy stem could be for those who regularly communicate with others around the world as am ateur radio 124 operators do The ability to explore different paths determine which ones cros s into the auroral zones and by how much as well as the changing ionospheric characteristics that occur along each path and the ability to see these changes in real time is
24. minimum step lengths will suffice under almost all circumstances Decreasing the se values may increase the accuracy of traced rays slightly but will slow down the computation s 3 3 18 11 Left Latitude Longitude of Display PROPLAB PRO s comprehensive ray tracing method requires a viewing window that encompasses the geographical region where the signals are being traced This win dow is defined by stating the latitude and longitude of the left side corner coordinates of the ray path and the right side corner coordinates of the ray path These two sets of corner coordina tes form a box within which the rays are traced PROPLAB automatically computes these corner coordinates for you so you will sel dom need to change them However if you ever do need to alter them this option and the option described in Section 3 3 18 12 below will let you do this 47 We do not recommend you play with these values unless you know what you are doing Doing so haphazardly could cause PROPLAB to incorrectly draw the display grids o r even fail to properly trace the rays No harm can be done however 3 3 18 12 Right Latitude Longitude of Display This option defines the latitude and longitude of the right side corner of the v iewing window described in Section 3 3 18 11 Refer to that section for details Positi ve values for both the left and right side corner coordinates of the window represent northern latitudes and western longitudes while negative v
25. modes can have advantages over single mode communication in that should one mode fail other mo des still exist to receive the signals on However larger numbers of modes or hops increase t he multipathing or the time spread between received signals Multipathing creates signal distortion since there may be several signals from the transmitter arriving at the receiver at slightly different times This can cause destructive interference distortion beating between the signals and strong to severe fading But for many types of communications these types of signal degra dation might not seriously impede the intelligibility of signals for example CW communications Other types of communications digital can be rendered useless with multipathing In Figure 8 1 there is almost a 3 millisecond range in reception times for sign als arriving at Colorado from Hawaii There is also a great deal of overlapping between signa ls of various types of modes For example at 7 1 MHz there exist three modes of propagation 3 hop 4 hop and 5 hop paths This is determined by scanning the graph vertically from the 7 1 MHz grid line and examining all those signals of differing colors that arrive at the receiver In this example there were three rays received at this frequency at approximately 18 4 milliseco nds ms 19 ms and 19 75 ms The time spread is therefore 19 75 18 4 about 1 35 ms between the slowest and fastest arriving signals This is a tolerable
26. of Critical E Layer Frequencies 79 4 6 Producing Maps of Solar Zenith Angles 05 80 4 7 Producing Maps of Magnetic DIP Angles 80 4 8 Global Maps of Magnetic Field Total Intensity 81 4 9 Global Maps of Magnetic Latitude 005 81 4 10 Producing Maps of Modified DIP Angles 81 4 11 Transverse Plasma Frequency Maps 0 00 81 SECTION 5 SIMPLE RAY TRACING SCREEN 04 83 5 1 Location Azimuth Distance of the Transmitter Receiver 84 5 2 UTC Time and Operational Frequency 4 4 84 5 3 CUR Lat and CUR Lon Statistics 0 0 4 84 5 4 Signal Air Distance Statistic 0 000 0 ee eee 84 5 5 CURrent Angle of the Signal 0 2 0 2 0 0002 eee 85 5 6 The Electron Density Graph and Numeric Density 85 5 7 Estimated Signal Strength Bar Graph 04 86 5 8 Signal Quality Bar Graph 20 00 02 ees 86 5 9 Magnetic Coordinates of the Ray 0 0 00 87 5 10 Solar Elevation Angle at the Ray Location 88 5 11 Height or Altitude of the Ray 0 2 0 2 eee eee 88 5 12 Plasma Frequency at the Ray Height 88 5 13 Signal Elevation Angle 0 cee ee ee ee tees 88 5 14 Auroral Zone Statistics 2 0
27. of day and sunspot number or solar flux value are all that is required PROPLAB produces the MUF graphs by first collecting the MUF data for the given p ath for every hour of the day Twenty four MUF values are therefore collected Durin g this phase PROPLAB shows you the UTC hour for which the MUF is being computed It also disp lays the progress of the computations by plotting a period a vertical bar and the letter e The period simply indicates that PROPLAB is busy working on the problem For paths that are greater than 4 000 kilometers and therefore require more than one hop PROPLAB computes two MUF values at two separate control points spaced approximately 2 000 kilometers from each end of the path These control points correspond to the path midpoints for one h op distances 4 000 kilometers from each end of the path When the first MUF is computed and t he second MUF is about to begin being computed PROPLAB prints the vertical bar The e i ndicates that PROPLAB is busy computing the E layer MUF for the control point in question 125 The Figure to the left shows an HOURLY MAXIMUM USABLE FREQUENCIES example of an MUF graph The MUF of the F2 layer is the top most line The next line down is the Optimum Working Frequency or FOT and is 85 of the MUF The thin line below the FOT is the numerical average of the MUF and the bottom line which is the E MUF also known as the E layer cutoff frequency For short distance tra
28. over many thousands of kilo meters The image is of relatively poor quality due to the dithering that was required Actual final maps are 94 filled with color not dithered The key in the center left and right sides of the figure define what each of the colors mean Unfortunately this is difficult to adequately discern in Figure 6 1 but shows you enough information for our needs Each individual color is associated with a range of signal quality numerical values ranging from 0 blackout or no signal NOSIG to 100 or extremely good signal quality Using this key you can determine MSN 7 See ee the quality of signals anywhere on the map ronosPHER BROADCAST COVERAGE MAP SIGNAL QUALITY 272 252 232 212 192 172 452 192 112 092 072 052 092 012 392 992 a12 Some very useful information can be Figure 6 1 Dithered High Quality Broadcast Coverage derived from this map For example areas Signal Quality Map where no signal is present are shown as areas having no filled colors The skip distance for this example is easily defined as the inner circle type boundary between no sign al and a strong signal Notice how the skip zone is elongated to the north and east away from th e transmitter in Colorado This is due to the failure of the ionosphere to reflect signals from the lower ionospheric layers E region for example perhaps brought about by the setting Sun Signal quality becomes very good just outside of the skip zone where MUF focusing
29. path Your first step would be to generate the broadcast coverage map using the material presented in Section 6 This would involve a fair amount of ray tracing activity After that process completed you would create the actual broadcast coverage map When this map is finished being drawn press the S key to save that screen image to the special disk format then return to PROPLAB s Main Menu Next select the option to generate global ionosp heric maps After this subprogram has been loaded you will again be presented with the ques tion of whether or not to use a previously generated map Inform the application to use the prev iously generated broadcast coverage map that was saved by pressing the S key PROPLAB will then automatically place that saved screen image on screen and will superimpose all m aximum usable frequency contours for 4 000 kilometer distances on that broadcast coverage map The resulting product is a map combining the broadcast coverage map with the maximum usable frequency contour map While this combined map is on screen you can press the S key again to save th at map to disk in the special format and use that map for superimposing other material upon For example you could superimpose contours of solar zenith angles on the combinatio n broadcast coverage and MUF map previously generated This time you may want to choose a d ifferent color for the solar zenith angle contours so that the solar zenith angle contours can be d
30. releases of PROPLAB may include an overlaid version that supports on the fly profile generat ion For the current version of PROPLAB the ionospheric profiles are not generated on the fl y but must still be provided in some way so that PROPLAB can in fact compute profiles for any distant point along a given azimuth The method described here is the simplest and most rapid method we could devise that does not sacrifice accuracy 58 The following discussion assumes a three dimensional ray tracing is being perfor med In a realistic three dimensional ionosphere the character of the ionosphere is constantly changing Electron densities which are major players in the refraction of radio waves vary widely from place to place They are high near the equators low near the poles highest near the magnetic equator in the afternoon lowest in the high latitudes near dawn and are constantly changing intensity These profiles however are extremely important if realistic rays are to be traced through such a dynamic ionosphere To generate Segment Segment 3 these profiles PROPLAB PRO splits up a specific path along a particular azimuth into a user Done priri ripete pebi priiipriripi mee defined number of a A E SEES a BRER BART DENI E NS cements ee T 3 1 Within each of these segments PROPLAB computes a user defined number of ionospheric Wi Single profile generated at each P line adjacent to bearing profiles Each of the compute
31. roral zone particularly during geomagnetic and auroral storms Sporadic E within the auroral zone is known as auroral sporadic E Auroral absorption or AA is a widely varying and almost completely unpredictab le consequence of auroral activity It can fluctuate widely both in time and space The maximum occurrence of auroral absorption appears to be just equatorward of the m aximum level of visible auroral activity It also maximizes in mid morning at a fixed location It can produce very poor to useless propagation between two points on a transauroral ci rcuit Auroral sporadic E when associated with geomagnetic storming is also known as storm sporadic E or storm E The occurrence of a thick storm E layer is known as night E and is not uncommon in the higher latitude regions during local nighttime This type of activity also varies widely in time and space and can enhanced E layer ionization by a substantial amount Often the intense ionization observed with this type of activity may be strong enough to reflect radio signals many times higher than usual It can therefore be a useful tool for propagating over longer distances using frequencies in the higher HF or even the VHF bands frequencies which would normally simply penetrate the ionosphere Electron density gradients within the auroral zones can vary significantly Hori zontal gradients can reflect radio signals in horizontal directions Horizontal refract ion causes non great ci
32. screen images to disk Results of ray tracing analysis or other graphical screen products can be saved to disk by pressing the G or P keys Pressing G causes PROPLAB to save the existing screen image to a GIF image file Pressing P forces PROPLAB to save s creen images to a PostScript compatible file This option lets you alter the way screen images are saved Screens can be saved to disk in a full color mode or a black and white mode The full color mode saves screens to disk in full color as they appear on your screen The black and white mode saves screen images to disk by first converting all non black pixels to white and leaving black pixels black The resulting screen is black and white and may work better if being printed on monotone print ers 3 3 18 Other Comprehensive Ray Tracing Options This option presents you with another full screen of modifiable ray tracing para meters that deal exclusively with the comprehensive ray tracing technique These option s are discussed in the following group of subsections 3 3 18 1 Ray Tracing Model Ray Type This option lets you change the type of ray tracing model that should be used when performing comprehensive ray tracings through the ionosphere There are five models available Four of these five models are based on formulas and techniques developed by Appleton and Hartree and are hence known as the Appleton Hartree models The fifth model is the Sen Wyller model This model produces si
33. section of the screen less frequently If you like to keep close tabs on the statistics then use a lower value The final three prompts deal with how the transmitter frequency is to be varied You are asked to type in the starting frequency the ending frequency and the frequency step rate to use during the ray tracing phase To analyze propagation conditions between the tran smitter and receiver between 1 0 MHz and 40 MHz use a starting frequency of 1 0 MHz and an ending frequency of 40 0 MHz The step rate you use here will determine the resolution of the results For high resolution use low step increments of say 0 25 MHz or less For faster computation and low resolution results use step rates of 0 5 to 1 0 MHz Keep in mind that as the step rate is increased the resolution of the results will decrease making it harder to s ee perhaps smaller features in the ionogram and perhaps decreasing the accuracy of the results in the process After you have responded to these prompts PROPLAB begins collecting the necessa ry data by rigorously ray tracing through the ionosphere from the transmitter to the receiver sweeping both the transmitter frequency and the elevation angle of the transmiss ion You can halt the data collection phase at any time by pressing the ESCape key Write down the current frequency and elevation angle being ray traced before aborting so you can continue the processing from that point later if you desire by appending the f
34. the sphere increases with distance along the outstretched ruler This statistic simply tell s you what elevation angle the signal is headed at It is measured from the horizontal position That is a zero degree angle denotes a signal travelling exactly horizontal toward the horizon A signa that is travelling at a 90 degree angle is directed straight up toward the zenith Positive angles are directed toward the zenith negative angles are directed toward the center of the Earth So as a signal travels through the ionosphere it will be associated with a positive angle of ascent in to the ionosphere Ionospheric refraction will gradually decrease this angle until it is travelling approximately horizontal after which further refraction will cause the ray to bend downward This is indicated by a negative angle value Negative 90 degrees is therefore pointing straight do wn The small box to the left of the geographical coordinates of the transmitter and receiver in the top left panel of the ray screen is a graphical representation of the c urrent angle of the travelling ray It shows the direction the ray is travelling both numerically graphically and textually The numeric value corresponds with the CUR Angle statistic The gra phical method shows the actual angle of the ray by projecting a straight line at the given ang le And the textual method is similar to the graphical method except a is used if the signal is travelling upward and a is
35. this can be useful to help you keep track of the cit y names 11 5 Commands Available While Viewing Maps There are several useful commands that are at your disposal while viewing maps in real time The standard screen saving functions G P and H keys can be pressed to save screens to GIF format PostScript format and to your local dot matrix printer r espectively You can also use your mouse to set new transmitter and or receiver locations The method used to accomplish this is identical to the method of setting up the tran smitter and receiver locations described earlier in this manual Press and release the left mouse button to define the transmitter location Then move the mouse pointer to the location of the receiver and press and release the right mouse button The great circle path distance and bearing are then instantly displayed on screen with X s marking the new locations for the transmi tter and receiver You can keep the transmitter fixed in location and change the receiver location by moving the mouse and pressing and releasing the right mouse button at each new desired re ceiver location This is desirable if you have several reception points you want to examine from one transmitter PLEASE NOTE that PROPLAB does not change the actual location of the transmitter and receiver that is used by the rest of PROPLAB s modules Changing the transmitter and or receiver locations in this real time mapping system module lasts only as
36. time delay for voice based com munications and is not too bad for digital communications either The maximum rate in bits per second of digital communications is approximately equal to the reciprocal of the range of multipath propagation times In this example then digital communications might be support ed on 7 1 MHz at a maximum rate of approximately 1 0 00135 741 bits per second or about 74 baud Note that this analysis is based on the data collected to form Figure 8 1 The accuracy of the assessment is therefore dependent on the amount of data collected From Figure 8 1 the highest signal qualities appear to be associated with the 2 hop mode of communications This is primarily the result of reduced distortion from low m ultipathing and relatively low signal degradation There are two regions where no signals were o bserved This void exists at about 14 0 to 14 5 MHz and again near 16 75 MHz Signals from Haw aii at frequencies near these voids would not be received at Colorado The maximum usable frequency MUF from Hawaii to Colorado is easily determined from Figure 8 1 The MUF is about 17 5 MHz This is a realistic MUF value that s urpasses the accuracy of the MUF computations available at PROPLAB s Main Menu Option 2 Why are these MUFs more accurate for paths greater than 4 000 kilometers PROPLAB computes the MUF in Main Menu Option 2 by computing the MUF at two control points approximat ely 2 000 kilometers away from the transmit
37. use a previously S aved map You there fore do not need to use only a previously saved broadcast coverage map but can use any map that was previously saved by pressing the S key while the map was displayed on screen If you choose to select a fresh map from the map library the next menu shows yo u the available maps in your map library and asks you to select one of those maps The next series of inputs defines the geographical location of the transmitter responsible for the data in the file PATHS OUT Type the geographical coordinates at the a ppropriate prompts PROPLAB produces the broadcast coverage maps by binning the data into groups of similar distances For example to determine the effects of ionospheric focusing and defocusing PROPLAB counts the number of individual rays that strike the ground within a spe cific area of the transmitter The default binning distance is 500 kilometers so PROPLAB coun ts the number of ground striking rays within a 500 km zone This zone is moved outward away from the transmitter at a specific user selectable Stepping distance rate until the zo ne is at the maximum distance previously defined when the broadcast map generation process was first started Following the input of the binning distance and the stepping distance rate you are presented with a menu and are asked to select the type of broadcast coverage map to generate signal quality multipath ranging etc Choose whichever map you need to
38. used if the signal is travelling downward If the signal is horizon tal a is used This may be useful in some cases where the angle of elevation is too small to be reliably depicted in the graphical display 5 6 The Electron Density Graph and Numeric Density The top central panel of the ray tracing display shows the electron density as the signal passes through the ionosphere This is a very valuable tool not only as a diagno stic device but also as an analytical device Using it you can determine why signals may behave the way they do or what conditions exist to refract a ray in a certain manner Since electron density behaves in an exponential fashion a logarithmic display is necessary to graph changes in electron density The electron density as a ray is being traced from one point to another in the ionosphere is graphed on screen using the same color that is used to trace the ray itself The base of the electron density graph begins at 1 0E 08 electrons per cubic meter and increases to about 2 0E 12 electrons per cubic meter The second logar ithmic division 86 is therefore at 1 0E 09 electrons per cubic meter followed by 1 0E 10 electrons per cubic meter etc Each subdivision is a tenth of a major division That is between 1 0E 10 and 1 0E 11 the subdivisions represent a change of 1 0E 10 electrons per cubic meter The numeric density can also be read directly off the top right side textual pan el of the ray tracing screen It
39. would be entered as M6 3 A magnitude X4 2 flare would be entered as X4 2 PROPLAB will not recognize flares in the A B or C class range since flares of these types are usually if not always incapable of producing any HF signal degradation Flares typically do not begin influencing propagation until they reach a class M 1 0 level Also it is worth noting that flares do not have significant impacts on the dark side of the Earth Only sunlit regions of the ionosphere are affected As a general rule the higher the Sun is in the sky the stronger the ionospheric impact will be from the associated flare x ray s Listen to radio stations WWV or WWVH for information regarding the state of the Sun at 18 minutes past each hour on 2 5 5 10 15 and 20 MHz Flares capable of in fluencing ionospheric radio communications exist when the recording states that solar activity was moderate high or very high Low and very low levels of solar activit y denote 24 hour periods of time where no flares of significance occurred Radio stations WWV and WWVH usually will not state the magnitude of observed flares To find out this inform ation you must either call the duty forecaster at the Space Environment Services Center at 303 497 3171 collect calls are not accepted call the Solar Terrestrial Dispatch BBS at 403 756 300 8 If you have access to the electronic Internet network you can obtain this information in ne ar real time maximum 3 hour re
40. 0 0 aaa aaa 88 5 15 Ionospheric Distance Travelled 2 00000 eee 89 5 16 Identifying the Receiver Location 0 0002 ce ee 89 5 17 Pausing and Skipping Traced Rays 00000 89 5 18 Aborting Ray Tracing and Saving Screen Images 89 5 19 Identifying Regions of Sporadic E 0 000000 90 SECTION 6 SIMPLE AREA COVERAGE MAPS 90 6 1 How are Broadcast Coverage Maps Constructed 90 6 2 Beginning Inputs 224 oie hee eh See ee be eek ei ands 91 6 3 Computing the Required Data 20 0 0 eee 92 6 4 Types of Broadcast Coverage Maps Available 93 6 5 Required Map Generation Inputs 0 0000 e eee 95 6 6 Available Commands while Viewing Maps 4 96 SECTION 7 COMBINING MAPS 0 0 0 0 eee ee 97 SECTION 8 ALL BAND SPECTRUM ANALYSIS 0 45 98 8 1 What is an Oblique Sounding Ionogram 99 8 2 Phase 1 Collecting the Required Data 99 8 3 Phase 2 Analyzing the Results 2 0 2 e eee eee 101 8 3 1 The Propagation Delay Plot 00 4 104 8 3 2 Elevation Angle Plots 0 000 108 8 4 Applying the Results 0 0 ce eee 110 8 5 Commands Available While Viewing Ionogram Plots 113 SECTION 9 COMPLEX AREA COVERAGE M
41. 0 kilowatt transmitter would be entered as 10000 This function of the Options Menu lets you set the transmitter power in watts It is used by both the simple and the comprehensive ray tracing techniques to compute the signal strength of the ray being traced The simple ray tracing technique produces signal strength results that are not rigorously computed but they do contain estimated effects of auroral absorption and other anomalies that can affect signals The comprehensive ray tracing method rigorously computes signal strength values based on actual computed ionospheric absorption values signal spreading loss etc Th e comprehensive technique will produce results that are more closely aligned with reality than the simple method except perhaps during geomagnetic storms as geomagnetic activity and auroral activity are not taken into consideration with the comprehensive technique as discussed earlier 3 3 8 Setting Ranges and Steps This option applies to both ray tracing techniques PROPLAB often requires a range of values or step values to use in performing cer tain functions For example when ray tracing signals from one point to another using elevation angles of between 0 and 20 degrees these values would be modified to cover the range and step values needed to complete the tracings In most instances you will not need to use this choice of the Options Menu The software will automatically prompt you for the appropriate ranges
42. 2 from Hawaii to a ship off the California co ast near 36N 126W on 11 5 MHz First determine what modes of propagation are possible on this frequency by scanning vertically up from the 11 5 MHz grid region There are three modes of communication possible on this frequency 1 hop 2 hop and 3 hop modes of commu nication The signal strength depicted in the upper panel of the figure suggests fair si gnal quality should exist on this frequency Signals requiring only one hop will likely have fairly strong signals However a strong signal can be associated with poor quality if multipathing is a factor And in this case multipathing will play a part in determining signal quality Signals that require 2 hops before reaching the receiver will have slightly less signal strength than single hop signals and will be out of phase with the stronger single hop signals by about 0 5 milliseconds This is a fairly small time spread and will not significantly degrade communications but may contribute to a slightly fuzzy level of voice communications Now consider the final mode of communications the 3 hop mode Notice that our 11 5 MHz frequency lies on top o f the MUF for 3 hop paths As a result the signal strength of the 3 hop signals may be st ronger than we might otherwise anticipate In addition these signals will require an additional 1 5 milliseconds from the time the single hop signals arrive before they reach the receiver This will introduce additional
43. 5 or 20 MHz In some instances it may be useful to convert the given K index value which is measure d every 3 hours to an associated A index value This can be done using the table of K A Indices given in Section 2 3 1 The Geomagnetic K Index For example since a middle latitude K index of 5 is associated with an a index of 48 the A index for that 3 hour interval would be 48 Using K indices in this manner to help compute shorter term A indices may or may not result in better short term determination of propagation conditions Success using this technique may vary from one event to another Overall PROPLAB is optimized to use the 24 hour A index value given by WWV and WWVH Quiet geomagnetic and ionospheric conditions are assumed to exist with A i ndices between about 5 and 10 Input values of 5 can also be used to produce monthly me dian results For example to create monthly median maps of critical frequencies or Maximum Us able Frequencies an A index value of 5 or lower should be used Use of higher A indi ces may give results that are not median in nature A median value is one which occurs 50 of the time 3 3 11 Setting the Sunspot Number or Solar Flux This option is used by both of the ray tracing techniques PROPLAB permits the entry of either the sunspot number or the 10 7 cm 2800 MHz solar radio flux This information is used to help determine the strength and intensity of ionization of the ionosphere To input th
44. 8 4 Applying the Results The foregoing discussion used the results of a night crossing signal path from H awaii to Colorado during geomagnetically quiet conditions and a low sunspot number In th is section we will apply the knowledge given in the last several sections toward understanding propagation conditions that exist on a new path Let s consider the path from Texas 30N 100W to the eastern U S 40N 75W at 1 8 00 UTC near local noon conditions on 25 December 1991 The transmitter is in Texas This corresponds to a geomagnetically quiet day geomagnetic A index of 7 The 12 mo nth mean sunspot number for this date was 109 In addition there were no flares or influ ential PCA present during this analysis Our antenna has a primary radiation pattern that extends from 0 degrees in eleva tion angle to about 50 degrees in elevation angle We therefore used as inputs to PROPLAB a starting elevation angle of 0 degrees an ending elevation angle of 50 degrees and we us ed an elevation angle step rate of 0 5 degrees In addition we swept the HF spectrum using a starting 111 transmitting frequency of 1 0 MHz and an ending frequency of 40 0 MHz with a fre quency step rate of 0 25 MHz 250 KHz The small step rates used increased the accuracy of the results but required quite a few hours of computation time for the ray tracing phase to finish Nevertheless the results are quite impressive and very informative i Figure 8 5 shows
45. AB therefore gives you the option of having the computer automatically calculate the time zone for you or allowing you to input the time zone manually If you choose the latter time zone information must be entered as a p ositive or negative integer reflecting the time difference between Universal time UTC and local time for the current transmitter geographical location Positive integers are used for locations that are west of Greenwich Negative integers are used for locations that are east of Greenwich For example Denver Colorado is west of Greenwich and therefore uses a positive integer value of 7 hours since the difference between local time and Universal time is 7 hours Similarly Sydney would use a value of about 10 hours During daylight savings time it may be necessary to include the adjustment in this time zone input When PROPLAB is configured to automatically compute the time zone information the acronym AutoZone is set to ON The status of this AutoZone variable can be determined at the main Options Menu If it is set to OFF manual input of time z one information is required each time the transmitter location is changed PROPLAB permits the selection of geographical locations by one of three different methods by numerical entry name entry or grid coordinate entry Numerical ent ries are those where the actual latitudes and longitudes are typed PROPLAB will also search through a geographical dictionary of locations city n
46. APS 113 9 1 Types of Broadcast Coverage Maps Supported 114 9 2 Type of Rays to Include 2 2 22 eae Sage ne See eRe RAE S ee 8 115 9 3 Specifying the Window Corner Coordinates of the Map 115 9 4 Specifying Limits for Collected Data 05 115 9 5 Other Map and Contouring Options 0 00 116 9 6 Database Offset Value nu kw SN READ Ba AE ORS 116 9 7 The Plotted Maps 32 63 25 ela ce 8 ON So eee AS ONS EN ROD oe EIS 117 SECTION 10 ANTENNAS oc4 os408 Oo oe Co ee oes ee Rea ea eee oe 8 118 10 1 Selecting Existing Antennas 2 0 0 0 eee eee 118 10 2 Displaying the Radiation Pattern 004 118 10 3 Creating Your Own Antenna Radiation Patterns or Modifying Deleting Existing Patterns 04 4 119 SECTION 11 REAL TIME MAPS 20 0 eee eee 120 11 1 Setting the Gray Angle 0 0 eee eee ee 121 11 2 Real Time Global Ionospheric Maps 4 121 11 3 Update Rates for the Real Time Maps 122 11 4 Displaying Local Times for Cities Around the World 122 11 5 Commands Available While Viewing Maps 123 SECTION 12 HOURLY MUF GRAPHS 0 2 0 00 eee eee 124 SECTION I INTRODUCTION 1 1 Introduction to PROPLAB PRO For years the ionosphere has been used as a major avenue of comm
47. F graph 125 MUF 3000 72 MUF fading 112 Multipath ranging 95 Multipathing 105 107 109 112 Nanotesla 8 Northern lights 9 Oblique Ionogram 99 102 Oblique ionograms 99 Oblique sounding ionograms 98 Omni directional 54 90 Options Menu 28 PCA 12 100 Penetration frequency 17 Perigee 56 Photosphere 4 129 Photospheric temperature 3 Plasma frequency 18 Polar Cap Absorption 12 cutoff latitude 12 diurnal pattern 13 GLE 12 riometer 12 Polarization 65 PostScript 41 113 Propagation after sunset 19 before sunrise 19 Propagation delay 95 Propagation delays 103 Proton flares 12 Radiation EUV 2 extreme ultraviolet light 2 lyman alpha 2 soft x rays 2 Radiation pattern 110 Radio Blackout cross identification 87 Radio waves history 1 Ray 14 Ray Tracing Screen impounding the signal 87 Ray tracing model 41 Ray tracing techniques 23 comprehensive or complex 24 simple 24 Real time mapping system 30 Receiver height 45 Reflect 1 Reflection 14 Refraction 2 14 definition 1 history 1 maximum 2 Rotating Grids 48 Satellite anomalies charging 6 130 tumbling 6 Save screen images 41 Scientific notation 86 Short Paths 32 Short wave fadeouts 80 SI 5 Signal quality 104 Skip distance 22 Skip distance focusing 115 Skip distances 22 Skip fading 94 Skip tracing rays 89 Solar elevation angles 79 Solar flares 5 100 locations 6 Solar flux 100 Solar radio flux 37 Solar wind 3 Solar zenith angle 73 S
48. O has not been tested very extensively under Windows 95 in a DOS mode It does however work for the most part under Windo ws 3 1 in DOS mode Keep in mind however that PROPLAB was developed for the DOS environment It will probably be ported over to Windows 95 in later releases 3 2 Running PROPLAB Changing Colors and Setting Up the Printer There are three different ways to execute PROPLAB from the DOS command prompt You may type PROPLAB and press ENTER or you can type PROPLAB and press ENTER The first command loads and runs PROPLAB permitting you to see the openi ng title page etc The second command loads PROPLAB but skips displaying the title page and instead takes you directly to the main menu of PROPLAB Use either of these two methods to run PROPLAB normally However the first time you run PROPLAB you should run it by typing PROPLAB and pressing ENTER The first time PROPLAB is run it gathers information about your current system configuration and writes this information to a file for future reference After you have run PROPLAB once you can select any of these t hree execution methods The third method of running PROPLAB permits you to change the colors text and graphics used in PROPLAB To do this type PROPLAB SETCOLORS and press ENTER PROPLAB then asks you to type in the new colors to be used by PROPLAB The VGA graphics employed by PROPLAB PRO allow up to 16 different colors to be displayed at the same time
49. PROPLAB PRO Version 2 0 High Frequency Radio Propagation Laboratory Copyright 1994 1996 by the Solar Terrestrial Dispatch USER S MANUAL TABLE OF CONTENTS SECTION 1 INTRODUCTION 26 oyieh Mu aS BGs oe Eee Raa ee GS ck eo eS 1 1 Introduction to PROPLAB PRO 0 0 00 SECTION 2 BACKGROUND 1 ene 2 1 The Ionosphere and magnetosphere 0 0000 e eee 2 2 Solar Terrestrial Relationships 0 2 eee 2 2 1 General Features of the Sun 02020000 2 2 2 Solar Activity and Solar Cycles 0 04 2 2 3 Flare Rating System 2 0 0 eee eee eee 2 3 Geomagnetic Indices 0 0 ee 2 3 1 The Geomagnetic K Index 0 00022 ee eee 2 3 2 The Geomagnetic A Index 0 000 eee eee 2 4 The Auroral Zones 40 5 edo hi 6 BOR FERS a Sill ON ERG AA OS AGS 2 4 1 Importance to HF Propagation 2 4 2 Auroral Phenomena lt 5 45 5 9 65 208 aie k Behe HAG RE ROE eR A Gs 2 5 Polar Cap Absorption PCA 2 0 0 0 eee 2 6 Ionospheric Radio Propagation 2 0 0 0 eee ee eee 2 6 1 Ionospheric Reflection and Refraction 2 6 2 Ionospheric Critical Frequencies and Heights 2 6 3 The International Reference Ionosphere 2 6 4 Propagation Paths 0 0 0 ce eee eee ee 2 6 5 Determining Propagation Condit
50. Selecting PROPLAB s Quick or Normal Modes 3 3 14 Selecting Plane or Spherical Grids 3 3 15 Selecting Grid Distances and Height Scales 3 3 16 Accounting for Solar Flares 004 3 3 17 Defining Polar Cap Absorption and Screen Saving Functions 3 3 18 Other Comprehensive Ray Tracing Options 3 3 18 1 Ray Tracing Model Ray Type 3 3 18 2 Magnetic Field Model 3 3 18 3 Collision Frequency Model 3 3 18 4 Electron Density Model 3 3 18 5 Integration Method 00050 3 3 18 6 Display Method 02000000 3 3 18 7 Transmitter Receiver Height 3 3 18 8 Ray Tracing Rate Steps per hop 3 3 18 9 Magnetic Pole Lat Lon 3 3 18 10 Maximum Minimum Ray Tracing Step Length Pa 3 3 18 11 Left Latitude Longitude of Display 3 3 18 12 Right Latitude Longitude of Display 3 3 18 13 Grid Distance and Ticks 3 3 18 14 Distance between Ticks in Altitude 3 3 18 15 3 D Rotation Angles for the X Y and Z Axes 8 3 3 18 16 Zoom Factors and X Y Axis Offsets 3 3 18 17 HMax and Altitude Grid Ym and foF2 Layer Shaping Factors 0 2 eee eee eee 3 3 18 18 Ground Gyrofrequency at the Equator 3 3 18 19 Electron Col
51. They c an be as large or as small as you like It may be useful to remember that most regions of sporadic E are fairly small in spatial extent covering an area perhaps several hundred kilometers in extent This is generally true except perhaps in the auroral zones where Es may be more widespre ad and cover areas many hundreds of kilometers in extent Polar regions of Es usually exist in bands or ribbons extending across the polar cap in roughly the direction of the Sun To quit defining regions of sporadic E press the ESCape key on your keyboard T he regions of sporadic E that you defined or edited removed will be saved to disk under the text file PROPLAB ES You can save screen images while in this mode by pressing the G P or S keys These functions save screen images in GIF image formats PostScript compatible f ormats or a special format as described below respectively Pressing S saves screen image s in a special format Such saved screen images can be used in other functions of PROPLAB to f or example superimpose contours of ionospheric characteristics or generate broadcast cover age maps Maps of different types can in this way be combined into a single image For example the screen image saved while in this mode provides positional information of the auroral zones the sunrise sunset grayline the position of the Sun the signal path and regions o f sporadic E Using this S ave function you can combine this map with conto
52. U3sz ot Figure 4 1 Global Map of Critical F2 Layer Frequencies Recall that the critical F2 layer frequency is the maximum frequency that can be reflected 76 vertically from the F2 layer Since the F2 layer is usually the main layer responsible for ionospheric signal refraction it is sometimes called the vertical penetration frequency because on frequencies higher than the F2 layer critical frequency vertically propagated signals will penetrate the ionosphere There are several features of interest to point out here Notice the high critic al frequencies near the equatorial region These enhanced foF2 values are known as the equatorial anomaly They occur within approximately 20 degrees of the magnetic equator not the geographic equator This is why the increased values tend to drift into South America away from the geographical equator the magnetic equator dips below the geographical equator and reaches a maximum difference near South America Regions where the sun is rising or setting produce pronounced changes in the ele ctron density profile that are easily discerned in the sample foF2 map given in Figure 4 1 for 19 00 UTC At this time it is near noon for the North American region and critical F2 layer frequencies and hence F2 layer ionization levels are at a maximum for the day Toward the west toward the sunrise sector the critical F2 layer frequencies begin decreas ing Critical F2 layer frequency gradients are strongest
53. ace Therefore during that time interval F2 layer propagation is not possible and you would be limited only to E layer propagation over shorter distances For most other times of the day communications is possible via the F layer beee only through narrow bands of frequencies Universal Tine of 95 10 10 The width of the usable frequencies increases substantially during the night time from 02 00 to about 12 00 UTC However levels of noise and absorption will definite ly be higher because of the depressed MUF values for that time period Communications on the higher bands is not possible except during daylight OPNVAUNNOY oooooo0o0000 OPNVAUNNOY ooooo0o00000 a fi f 3 5 a gt LU uc f c3 oo rad rad ou ec a6 Cn aw rad re u No E E 5o Za oe og oa 9 pE 27 u FA a 4 i 2 5 o E m 3 H Q j o 2 i F a a T N While viewing the graphical results you can press G or P to save the result s to GIF or PostScript files respectively You can also print the results on your dot matrix printer by pressing the H key Press any other key to return to PROPLAB s Main Menu A index 8 100 Absorption 111 Altitude grid adjusting the height 50 Angles of elevation 109 Antenna template 119 Antennas 90 118 acronyms 119 creating 119 directional 54 omni directional 54 Apogee 56 Aurora australis 9 Aurora borealis 9 Aurora Zone aurora borealis 9 Auroral absorption 11
54. ach the recei ver are not as tight Using this information you can construct antennas that avoid undue multipathing effects For example if an antenna was constructed to transmit most of its radiated power between elevation angles of 5 and 18 degrees most of the radiated power would reach the receiver in 2 hops The narrow transmission angles used would eliminate most of the multipathi ng interference that might occur with the single hop 3 hop 4 hop and 5 hop propagation modes resulting in improved signal quality at the receiver Another way to use this information is to analyze how much multipathing might oc cur on specific frequencies with a given antenna For example an antenna that trans mits most of its power between 10 and 30 degrees would see up to 3 propagation modes 2 hop 3 ho p and 4 hop propagation modes To reduce multipathing effects and distortion Figure 8 3 sug gests that frequencies between 11 75 and 15 25 MHz should be optimum The 3 and 4 hop MUFs are surpassed at 11 75 MHz and are no longer a problem reducing multipathing substantially and improving signal quality The 15 25 MHz upper limit defines the 2 hop MUF Frequ encies above 15 25 MHz therefore will penetrate the ionosphere before reaching the receiver Single hop signals are not possible because the angles of elevation required to reach t he receiver using the single hop mode of propagation are not within the radiation pattern of the transmitting antenna For thes
55. acing method Use the comprehensive method for more accurate signal strength computati ons 5 8 Signal Quality Bar Graph IMPORTANT PROPLAB PRO Version 2 0 uses a new signal quality measuring stick This was required because PROPLAB now computes estimated signal strengths as opposed to strict quality figures derived from appropriate estimated models This new measuring st ick attempts to relate signal strength with signal quality and also considers other degrading parameters that affect the quality of signals PROPLAB measures signal quality as a numerical value between 0 and 100 A value of 100 represents the best possible conditions extremely good while a value of z ero represents complete signal loss or radio blackout conditions PROPLAB converts the numerica 1 value to a color coded bar graph for easier interpretation Areas within the blue region are associated with very good to good propagation Areas within the green section represent signal q ualities that may vary from good to fair The yellow section of the bar graph corresponds to signa ls that may vary in quality from fair to poor And signals that vary from poor to blackout condit ions occur within 87 the red area of the bar graph The numerical value of the computed signal quality is also converted into a textual representation of signal quality This textual representation is displayed on the top right panel of the ray tracing screen to the left of the acronym Sig Qual The
56. adiated in a field that lies between 4 and 12 deg rees in elevation Now you want to determine propagation quality of a signal being propagated from your location to a distant region 3 000 kilometers away but you are uncertain whether your tr ansmitter will be able to send a signal that distance Using this first function to sweep elevation angles you can set up PROPLAB to begin tracing rays through the ionosphere beginning at an elev ation angle of 4 degrees and ending when the elevation angle reaches 12 degrees The step rate you choose to use is entirely up to you If you want PROPLAB to trace 3 rays on screen betw een this range you would select a step rate of 4 degrees of elevation per trace For 16 traced rays and hence greater resolution in the results you would select a step rate of 0 5 degrees of elevation per traced ray The usefulness of sweeping elevation angles is not restricted to the above examp le There are many other useful ways to use this function For example if you need to kno w exactly what distance your signal strength is a maximum on a given frequency you would selec t this option to sweep elevation angles Since signal strength is proportional to the concentr ation of rays that strike the ground per unit area you would look for a pattern similar to Figure 2 5 where the rays become concentrated The area where the rays are most concentrated is the location and distance of maximum signal strength Another way to use th
57. adius of the Sun is 109 times larger than the radius of the Earth or about 696 000 km It takes approximately 27 days for the solar equatorial regions to complete one rotation We could fit over 1 3 million Earths inside of the Sun The Sun is composed of an interior region which lies below the visible photosphe re Above the photosphere lies the chromosphere or lower solar atmosphere The corona forms the outer atmosphere of the Sun About 99 9 percent of the Sun is composed of hy drogen and helium and of these elements hydrogen is by far the most abundant 92 1 The photosphere of the Sun represents that region of the solar atmosphere where the gaseous density increases rapidly to the point where features below the boundary of the photosphere appear opaque The temperature above the photosphere falls to a value of about 4200 K approxima tely 5000 km in altitude Thereafter the temperature increases to approximately 1 to 3 million degrees Kelvin in the coronal regions 2 2 2 Solar Activity and Solar Cycles With the naked protected eye the Sun appears as an almost featureless disk However using telescopes it has been determined that this is not true The Sun contains many different types of phenomena Perhaps most significant are the appearance o f Sunspots Sunspots were first discovered by Theophrastus near 325 BC These dark spots form and disappear over time intervals ranging from less than a day to several months Su nspots appear
58. al frequency To select another region move the mouse to the desired location and click on the LEFT mouse button again If you decide you do not want to define a region at the loca tion marked by the left mouse button press the left mouse button a second time to deselect the marked region To remove a defined and superimposed sporadic E region move the mouse cursor so that it lies somewhere overtop of the displayed sporadic E region and click the RIGHT mouse b utton This will remove any defined sporadic E region Sporadic E regions can be superimposed on other regions of sporadic E If you do not have a mouse available the rectangular geographical coordinates of the sporadic E regions can be inserted into the text file PROPLAB ES in the follow ing format Top Left Latitude Top Left Longitude Bottom Right Latitude Bottom Right Longitu de Critical Frequency The quoted section must reside on one line as follows 45 32 105 4 40 67 85 7 6 0 In this example the top left geographical coordinates of the rectangular sporad ic E region are 45 32 degrees north latitude and 105 4 degrees west longitude Similarly the b ottom right geographical coordinates are 40 67 degrees latitude and 85 7 degrees longitude The critical frequency of this region of sporadic E is 6 0 MHz 70 With or without a mouse you can define up to 99 individual regions of sporadic E There is no limit on the geographical spatial extent of each individual region
59. al time lag by using the finger command finger solar solar uleth ca or by anonymously FTPing to the machine solar uleth ca and grabbing the file in dices doc from the directory pub solar Indices A World Wide Web page will also become availa ble very shortly and may already be in operation Contact COler Solar Stanford Edu to find out what this address is 3 3 17 Defining Polar Cap Absorption and Screen Saving Functions The Polar Cap Absorption section of this option only applies to the simple ray tracing technique The Screen Saving Functions apply to both the simple and the complex techniques The last choice of the Options menu gives you the ability to define the magnitude or existence of Polar Cap Absorption or PCA at the given date and time PCA can have devastating impacts on transpolar and transauroral circuits 41 PCA measurements can be entered directly into PROPLAB in units of decibels dB absorption At the PCA input prompt press ENTER if no absorption exists The existence of PCA can be determined by listening to radio stations WWV and WW VH at 18 minutes past each hour on 2 5 5 10 15 and 20 MHz Although they don t report the magnitude of PCA present magnitude information can again be obtained from the s ame sources as given previously in section 3 3 16 Refer to that section for more informatio n on the available sources This choice of the Options menu also lets you alter the way PROPLAB saves graphic
60. all of the light is totally reflected toward the other side of the prism The same principle applies when the ray of light strikes the second side of the prism Since the ray also strikes this second side at a 45 degree angle total reflection occurs again causing the light to strike the same surface that it first passed through in a direction opposite and parallel to the emergent ray Figure 2 1 Total Internal Reflection in a Porro Prism In order to understand how radio signals are refracted in the ionosphere it is necessary to have an understanding of the radio refractive index of the ionosphere Sir Ed ward Appleton is usually the person to which the radio refractive index is attributed Appleton was responsible for much of the work which led to the computation of the radio refra ctive index It is therefore popularly known as the Appleton formula Contributions by others have also 16 led to modified names such as the Appleton Lassen formula or the Appleton Hartr ee formula Here we will refer to it as the Appleton formula The ionosphere is composed mostly of electrons and ions The heavier ions do not influence the refractive nature of the ionosphere as much as the electrons For this reason considering only the electrons is accurate enough when considering the refractiv e index of the ionosphere As was mentioned previously glass refracts rays of light because glass is dense r than air Likewise a ray of light in open space
61. all of the tools req uired to fully analyze all of these quantities It will produce maps showing you the location of the auroral ovals the location of sporadic E the path travelled between the transmitter an d receiver as well as maps showing maximum usable frequencies and signal qualities However all of this information is not available on a single map You would normally have to generate each map for each quantity separately and then reference each separate map individually PROPLAB gives you the power to combine maps or superimpose data onto previously constructed ma ps Each time a graphical image is displayed with the exception of the ray tracing screen you have the option of pressing the S key to Save the graphical screen image in a special 98 format to disk This is the key to combining maps Every time an application runs that may result in a generated map the question is first posed do you want to use a pre viously generated map or a map from the map library To use a map that has been previously saved in the special format choose the option to use a previously generated map That application wi ll then use the map saved to disk in the special format instead of pulling out a fresh map from the map library This is the process used to combine maps Let s say you want to generate a broadcast coverage map showing you the quality of signals within the broadcast area as well as global maximum usable frequencies for a 4 000 kilometer
62. alue must be on the right side of an equal sign The left side of the equal sign must contain the elevation angle for which the gain value applies In actuality the values following the VGAJN acronym are loss values that are relative to the maximum gain of the antenna defined using MAXANTENNAGAIN For example if the maximum gain of an antenna is 24 dB and the VGAIN value entered at an elevation angle of 10 degrees is 20 dB then the actual gain of the antenna at that angle of elevation would be only 4 dB 24 dB minus 20 dB A value of zero dB would correspond to an antenna gain of 24 dB A value of 30 dB would correspond to an antenna gain of 6 dB or a loss of 6 dB Be careful when entering radiation pattern values here All values must be relative to the maximum gain of the antenna It is therefore impossible to have VGAIN values that are negative for this would imply that the antenna had gains that exceeded the maximum specified gain of the antenna and this is not possible HGAIN This acronym is used to mark the beginning of the values that describe the radi ation pattern of the antenna in the azimuthal plane There must be 360 numerical value s that follow the HGAIN acronym On each of these lines there must be two values separated by an equal sign with the HGAIN value describing the signal strength gain in dB relative to the maximum gain of the antenna on the right side of the equal sign and the azimuth on the left side Exactly t
63. alues represent southern latitudes and easter n longitudes 3 3 18 13 Grid Distance and Ticks This option applies primarily to the three dimensional display grids on which ra ys are traced It lets you specify the maximum grid distance to display on screen This distance must be less than or equal to 20 000 kilometers Since PROPLAB PRO s comprehensive ra y tracing engine will only trace short paths and since the half circumference of the Earth is 20 000 kilometers this maximum permitted grid distance corresponds to the maximum trac eable short path distance It should suffice for most applications For example if the distance between the transmitter and receiver is 7 000 kilom eters it would be wise to specify a grid distance of at least 7 000 kilometers or more If you specify a distance less than 7 000 kilometers the receiver location will not be included on the grid It would be wiser to specify distances that are several thousand kilometers greater than the transmitter receiver distance so that ray s which do not precisely reach the rec eiver distance will continue to be traced until they hit the ground some distance beyond the receive r It is generally good practice to specify a distance approximately 4 000 kilometers beyond the receiver This corresponds to the approximate maximum one hop limit The two remaining prompts let you define how PROPLAB should label the grids The first of these two prompts asks you to specify the distance bet
64. ames or other aliases and accept matching entries if you have enabled the AutoQTH function For example if the geographical dictionary contains Orlando s geographical coordinates you can inform PROPLAB to automatically grab Orlando s coordinates from the geographical dictionary by sim ply typing Orlando or orlando or ORLANDO or oRLaNDo at any of the prompts requestin g the Latitude or Site Name The names are case insensitive 30 The geographical dictionary is located in the file PROPLAB LOC This is a simp le text file that can be edited with a standard text editor or word processor Line s prepended with an asterisk are treated as comments Each line of this file must follow this format CITY NAME LATITUDE LONGITUDE TIME ZONE For example Philadelphia 40 0 75 0 5 is a valid entry defining the approxima te location of Philadelphia At any of PROPLAB s prompts requesting a Latitude or Site Name yo u could type Philadelphia and PROPLAB would automatically enter the latitude and longi tude values as 40 0 and 75 0 respectively The 5 defines what time zone Philadelph ia is located in In this case Philadelphia is 5 hours different than Universal Time or the time reckoned from Greenwich England Mountain Standard Time is 7 hours Pacific Standard T ime is 8 hours etc The third method of entering in locations is using the grid location method This method is popular amongst people who frequent the VHF and UHF b
65. an invaluable addition to PROPLAB SECTION 12 HOURLY MUF GRAPHS Most radio propagation programs are capable of displaying the maximum usable fre quency MUF as a function of time PROPLAB is no longer an exception PROPLAB PRO Vers ion 2 0 will now compute and graph the maximum usable frequency between a given tran smitter and receiver over a period of 24 hours It will also graph several other important lines at the same time which will help guide the user into selecting appropriate transmission or reception frequencies The hourly MUF graphs are produced by using the simple ray tracing technique to search for and locate MUFs and E layer maximum usable frequencies The E layer MUFs are critical for determining the lowest frequency which will penetrate the E layer This is important for long distance communications because long distance communications can only be accompl ished if the signals are reflected from the F layers which reside above the E layer Signal s must therefore be high enough in frequency to punch through the E layer but must also be low enough in frequency to be reflected by the F layers and not penetrate them These graphs a re ideal for these purposes and give you a good idea when specific bands may open or close through the course of a day There are no required prompts to produce an MUF graph The only parameters requi red are set within the Options menu Main Menu Option 8 The transmitter and recei ver locations time
66. and more serious distortion into the received waveforms degrading the received signal a bit more In this case the given signal quality may in actuality be close to fair on 11 5 MHz Notice how the quality suddenly improves goes to higher numbers as soon as the MUF for 3 hop signals is passed At 12 0 MHz the signal quality jumps up to good values primarily because the additional distortion introduced by the 3 hop signals is no longer present Only 2 modes of propagation are possible at 12 0 MHz single hop and dual hop co mmunication modes The relatively small multipathing 0 5 ms that exists between the 1 hop and 2 hop signals is in this case negligible It is interesting to note that the decreas e in propagation delay time spread between 11 5 MHz 1 5 milliseconds and 12 0 MHz 0 5 milliseconds would have a significant impact on the maximum speed of digital communicators In this inst ance the reduction in multipathing would increase the maximum speed of digital communicat ions by about a factor of 3 simply by judiciously choosing low multipath frequencies This illustrates a small portion of the value of performing an oblique ionogram type of signal path study Figure 8 2 still shows a region where no signals were received near 15 0 to 15 5 MHz Notice that the void in the frequency spectrum has increased in frequency from F igure 8 1 where it resided between about 14 0 and 14 5 MHz to Figure 8 2 The fact that this re gion of bla
67. and steps 3 3 9 Selecting Local or Universal Time This option applies to both ray tracing techniques Using this choice of the Options Menu you are able to change the type of time u sed in PROPLAB Local time is the time you set your alarm clock to when waking up in the morning Universal time is reckoned from Greenwich England It is the time on which all o ther times around the world are based Universal time is the same for everyone everywhere Universal time can be determined anytime of the day to the second by listening to radio stations WWV 37 and WWVH on the shortwave frequencies 2 5 5 0 10 15 and 20 MHz There are ot her equally accurate clocks on the broadcast bands but those mentioned above are the most accessible Select whichever type of time you need to use If you use local time PROPLAB wi Il convert it when necessary to equivalent Universal Time using the Time Zone infor mation described earlier All dates and times entered into PROPLAB will be reckoned acc ording to the type of time selected here 3 3 10 Setting the Geomagnetic A Index This option is only used by the simple ray tracing method and several of the supporting PROPLAB functions such as the real time mapping system The geomagnetic A index describes how active the geomagnetic field is at a given time The value which should be used here can be found by listening to radio stations WWV or WWVH at 18 minutes past each hour on the frequencies 2 5 5 10 1
68. ands This method divides the Earth into hundreds of small 2 degree wide squares Each square is given a special fixed name or designation such as DN43ah To use grid square designati ons at the prompts requesting Latitudes or Site Names simply prepend the grid square name with an exclamation mark For example DN43ah PROPLAB will then automatically co nvert this grid square name into the appropriate geographical latitude and longitude c oordinates 3 3 2 Graphically Setup Transmitter Receiver Locations If your system is equipped with a mouse you can graphically set the position of the transmitter and receiver using the third option of the Main Menu in PROPLAB Se tup Sporadic E Xmit Recvr Locations To use this feature a Plate Carree map proj ection must exist in the map library If the map exists it is displayed on screen along with the location of the mouse cursor the location of the auroral zones the location of the sunrise sunset terminator or grayline and the location where the Sun appears directly overhe ad PROPLAB PRO also lets you plot an additional line that marks the regions of the world where the sun is a specific number of degrees above or below the horizon For ex ample you can now instantly determine the regions of the world where evening and morning t wilight is beginning or ending by telling PROPLAB to plot a line which marks the locations where the sun is say 12 degrees below the horizon This is accomplished
69. ange most are between 1 and 100 MeV in energy These very high energy particles may penetrate much deeper than usual and produce what is known as a Gr ound Level Event or GLE where neutron monitors at ground level experience sudden in creases in neutron levels brought about by the deep penetration of these high energy partic les PCA s typically last anywhere from about an hour to several days with an average of around 24 to 36 hours The intense ionization of the lower ionosphere results in heavy absorption of HF radio signals The absorption associated with PCA is measured b y an instrument known as a riometer or relative ionospheric opacity meter This is basically a radio receiver tuned to receive galactic radio noise on a frequency of about 30 MHz using a vertically directed antenna A higher frequency would be useful to avoid deviati ve effects but on higher frequencies galactic noise levels and ionospheric absorption levels decrease On a frequency of about 30 MHz absorption changes of about 0 1 dB can be reliably measured To give an idea of how devastating PCA can be consider what might happen to a signal if the PCA measured over a polar region was 13 dB This would produce att enuation of approximately 170 dB for a 10 MHz signal reflected from the F layer This is sufficient to produce complete signal loss for lower power non commercial transmissions and very heavy attenuation of signals even from the large and powerful commercial tr
70. ansmitters PCA appears first over the polar regions It then expands equatorward to a magne tic latitude of approximately 65 degrees The latitude where the ionization produced by the incoming protons subsides is known as the cutoff latitude PCA therefore covers the entire polar region down to about a geomagnetic latitude of 65 degrees This can signif icantly impact transpolar and even some transauroral circuits PCA is not related to auroral activity or geomagnetic storming Flares which pro duce 3 The riometer a device for the continuous measurement of ionospheric absorption Proc 1 R E 47 page 315 13 proton events are almost always associated with coronal mass ejections which can often have a dramatic geophysical impact However since the protons travel at much higher velocities than the flare related shockwave the protons usually result in PCA for between 24 to 36 hours before the flare related interplanetary shock reaches the Earth After the shock front passes the Earth the density of the high energy protons gradually diminish toward pre event background levels PCA therefore usually ends a few hours after the arrival of the main shocked disturbance However the level of geomagnetic storming which follows the shocked disturbance is frequently strong enough to maintain very poor to near useless pr opagation over the polar regions PROPLAB will take polar cap absorption into consideration when computing signal quality
71. at deal about how the ionosphere responds to different signals For example by sweeping frequencies you can determine what frequency to use to penetrate th rough dense layers of sporadic E or through other ionospheric layers Since long distance c ommunications occurs best through F2 layer reflections sweeping frequencies can help you determine what frequencies to use to penetrate through the D E and F1 layers for reflection f rom the F2 layer During the day when ionization of the D E and F1 layers is highest this soft ware feature can significantly help you isolate optimum frequencies for specific paths Sweeping time from hour to hour or minute to minute lets you analyze the behavi our of the ionosphere over time and how it responds to the signals you transmit This is a very useful feature for determining what times of the day certain frequencies open up for lo ng distance communications or for observing what happens for example at sunrise or sunset and how signal propagation radically changes during these periods of time The fourth option available in this Ray Tracing Menu Generate Oblique Sounder Ionogram is a powerful function that requires an entire section within this man ual to adequately describe Refer to Section 8 for details regarding this function 3 4 1 2 Ray Tracing Signals using the Comprehensive Ray Tracing Technique The menu associated with the comprehensive ray tracing technique lets you trace rays through the ion
72. ath That amounts to one profile every 326 kilometers 15000 46 326 This means that each successive ionospheric profile is separated by 326 kilometers In order to prevent gaps in data from appearing PROPLAB must perform interpolation when rays are in between ionospheric profiles as would occur if a ray was part way between profiles that were spaced 326 kilometers apart This interpolation process is a source for possible inaccuracies in traced rays The level of inaccuracy is proportional to the distance separating ionospheric profiles In other words the closer the spacing in distance is between successi ve ionospheric profiles the more accurate the ray tracing will be A spacing of 326 kilometers is a fairly hefty distance The character of the ionosphere may change appreciably within this dis tance Therefore it would be wise to decrease the spacing between ionospheric profiles so that we obtain a more realistic sampling of the ionospheric characteristics In this example we are unable to decrease the distance between ionospheric profiles because we are alre ady using the maximum allowed number of profiles 46 We are in luck however because PROPLA B will let you split up the 15 000 kilometer path into up to 9 segments as illustrated in Figure 3 1 It will then let you generate up to 46 ionospheric profiles within each segment This gives you the ability to sharply increase the number of profiles generated over the 15 000 kilometer path
73. ause a polar map projection includes only half the surface area of a global Lambert projection which permits PROPLAB to compute ionospheric parameters for more of the available surface area A polar projection only includes those geographical area s that are either north or south of the equator A Lambert projection includes both the north and south hemispheres and hence twice the surface area Ionospheric profiles must therefor e be computed for larger spatial distances when larger spatial areas are included For greatest spatial resolution select the highest available resolution levels and use polar map projections PROPLAB gives you full control over how contours are to be labelled One of the common inputs required defines how you want contours to be labelled The default is to label all contour lines You can also instruct PROPLAB to label only every Nth contour only the lowest and highest valued contours or not to label any contours at all Usually you will want to label all contours although in cases where the labelling from contours may overlap one another it may be useful to label only every other contour etc The choice is yours PROPLAB also asks you for the minimum value to contour the maximum value to contour and the stepping rate for contouring between the minimum and maximum values For example to create a global map of MUFs with contours defining the 5 10 15 20 25 and 30 MHz MUF zones you would specify a minimum contour va
74. by specifying a value of 12 as the angle for the sun Negative values represent angles below the horizon Po sitive values represent angles of the sun above the horizon A value of zero then represents the locations around the world where the sun is exactly setting or crossing the horizon This is an extremely powerful function that lets you visually determine precisely the proxi mity of your chosen radio path to the various zones of influence PROPLAB PRO Version 2 0 is now equipped with another major function which will let you plot these various zones of influence in real time Consult the appropriate section of this manual dealing with the real time mapping system 31 To set a new transmitter receiver location pair move the mouse cursor to the po sition of the transmitter and click on the left mouse button to mark that location The n move the mouse to the location of the receiver and click on the right mouse button The g reat circle path between the two points will then be traced on screen along with updated pos itions of the auroral ovals the grayline and the Sun if local time is being used You can alternatively keep the location of the transmitter constant and change t he position of the receiver by moving the mouse to the new location of the receiver and clicking on the right mouse button This will only change the position of the receiver an d will leave the transmitter location constant This powerful feature of PROPLAB permits
75. ces must be in kilometers For example inputting a Grid Distance or Ground distance of 4000 km and a Grid Height of 400 km would when tracing rays display a grid 4000 km wide by 400 km high It is important to realize that the grid distance should be at least as large as the distance between the transmitter and receiver If the given grid distance is too small traced rays will never reach the receiver but will be forced to stop when they reach the edge of the grid boundaries For example if the distance between the transmitter and receiver is 7000 km and you specify a grid distance of only 6500 km the rays will hit the edge of the grid at 6500 km and will never reach the receiver 500 km beyond the end of the grid To rectify this situation a grid distance of at least 7000 km should be used 40 3 3 16 Accounting for Solar Flares This option is only valid for rays traced using the simple method The existence of solar flares during the time when signals are propagating throu gh the ionosphere can have a significant impact on the quality of signals Solar flares can result in strong absorption of signals in the lower ionosphere particularly below the E ayer PROPLAB lets you input the magnitude of a flare that may be influencing propagat ion at the given date and time The value you enter must be a valid flare magnitude as was described previously in the Flare Rating System see section 2 2 3 For examp le a magnitude M6 3 flare
76. cify the distance ahead of the transmitter in kilometers to end ionospheric profiles The total distance specified here defi ned as the distance ahead of the transmitter minus the distance behind the transmitter determines the length of one segment as described in Section 3 4 1 3 PROPLAB next asks you to specify the number of individual ionospheric profiles y ou want to build along the total distance of the specified segment You can instruct PROPLAB to build up to 46 individual ionospheric profiles along the length of a segment It therefore defines 53 the resolution of the ionospheric profiles used in three dimensional ray tracing For example if the total distance of a segment was 8 000 kilometers and you state that you want to build 20 profiles along this distance PROPLAB will generate one ionospheric profile ever y 8000 20 400 kilometers The resolution can be increased by increasing the number of prof iles from 20 to 46 This reduces the distance between individual successive ionospheric profiles from 400 kilometers to 174 kilometers The last prompt posed by PROPLAB asks you how many segments you want to build ionospheric profiles for along each bearing In the above example if we specified 2 segments each of which is 8 000 kilometers in distance we would be able to trace rays along any of our bearings out to a distance of 8000 x 2 16 000 kilometers After answering these prompts PROPLAB is ready to begin building ionosphe
77. cing your region or your signal path Type the critical frequency of the sporadic E layer in MHz at the prompt reque sting this information being guided by the data available from the daily ionospheric reports or by estimating the values according to the guidance given in the preceding paragraph s Keep in mind that sporadic E is very often associated with the auroral zones During active or storm periods of geomagnetic activity the auroral zones may be filled with regions of sporadic E The equatorial regions are also areas where frequent sporadic E can occur particularly during the daytime hours Middle latitudes observe sporadic E more during the equinoxes and geomagnetic storms but are not restricted to these times Sporadic E can occur almost anyti me and anywhere Areas within and poleward of the auroral zones are often associated with regions of enhanced E layer ionization corresponding to critical E layer frequencies of about 1 5 MHz High latitude regions may observe night time periods of E layer critical frequencies of this magnitude on a near daily basis During the night the critical frequency of the E layer usuall y drops to about 0 4 MHz Critical frequencies of 1 5 MHz are sufficient to affect some low band frequencies After the critical frequency of the defined rectangular sporadic E region has be en entered the map is redrawn with the newly defined region of sporadic E superimposed on t he map along with its associated critic
78. ckness in the frequency spectrum was also evident in the 5 300 kilometer pl ot in Figure 8 1 suggests that the anomaly is in all likelihood real and should be avoided We could not be so 108 certain of this if the density of traced rays during the data collection phase was low In these examples a sufficient number of rays were traced to produce reasonably realistic and accurate results 8 3 2 Elevation Angle Plots E Figure 8 3 is a plot of elevation angles with frequency as opposed to propagation delay time with frequency It was derived from exactly the same data as Figure 8 2 for the 3 500 km path from Hawaii to the ship at 20 36N 126W o 41 54 ERREN DUDWNE Signal Quality 28 08 x 34 62 1 gaam 5 H In a nutshell this plot shows you what fuss ope Hop i transmission angles of elevation are required fs zsh LL es Hop 20 77 H for signals to reach the receiver at 36N 126W fia on specific frequencies throughout the HF ka U 158 20 125 95 21 40 Lon 35 61 Lon OBLIQUE SOUNDING IONOGRAM i f T i spectrum Itis an extremely valuable tool for ae ater k X determining optimum transmission takeoff 0227 1 gt 71 6 ea Aiie io 2 AA n 7S 50 0 angles to remote locati
79. d profiles Figure 3 1 How PROPLAB Segments Paths and Computes Profiles contains several other profiles immediately adjacent to the main bearing of the signal Figure 3 1 shows this in greater detail The top part of this figure shows the entire path divided into 3 segments The inset shows a part of Segment 1 in greater detail In the inset the solid line represents the main bearing the great circle path of the signal In order to compute the spatial gradients of electron density along this main beari ng it is necessary to know the ionospheric characteristics immediately adjacent to this main bearin g So PROPLAB computes ionospheric profiles along successive sections of each segment as shown by the P lines in Figure 3 1 Along each of these P lines adjacent to the main bearing PROPL AB computes profiles a short distance from the main bearing as indicated by the small squares along the P1 and P10 lines Although it is not shown profiles are computed in similar locati ons along each P line Segment 1 So now PROPLAB knows the ionospheric profiles along the main bearing and it also knows the characteristics of the ionosphere at small distances away from the main bearing This is all of the information that is necessary for signals to be traced in three dimensions since it allows us to compute all of the required spatial gradients of electron density along the path the signal travels provided it does not deviate from the given azimut
80. d within a specified binning distance de scribed shortly Transmissions that are digital in nature may find the multipath ranging maps exc eptionally useful Digital transmissions are not as dependent upon the quality of a signal path as they are upon the multipathing that is occurring over the path Digital information canno t be transmitted at high speeds if multipathing is occurring because multipathing causes the pul ses or packets of transmitted information to become entangled with each other and or distorted into garbage Multipathing is what happens when one or more signals travel different paths to the same destination Each signal takes a specific amount of time to reach the destinatio n For signals that travel farther to reach a given destination the signal will arrive at the desti nation sooner than a signal that travels a shorter distance to the destination The time difference b etween arriving signals is what causes multipathing and is also what is responsible for limiting the speed and or quality of digital transmissions For digital communications paths with the low est possible multipath ranges or time spreads of arriving signals are desired These areas typically tend to occur near the maximum usable frequency provided all of the signals are being reflected from a single ionospheric layer this usually occurs near the MUF anyway PROPLAB will produce broadcast coverage maps of multipath ranging information showing you the ti
81. dark because the temperature about 3000 K within the dark regions is lo wer than that of the surrounding hotter and therefore brighter gas If a sunspot were removed from the Sun and placed in orbit some distance away from the Sun it would appear as a ve ry luminous object All sunspots and other features rotate from east to west Both the Sun and the Earth rotate in the same direction and the Earth orbits around the Sun in the same direction as the Sun rotates The Earth is a solid body and rotates from east to west at the same rate over all of the Earth The Sun however is a gaseous body and rotates faster at the solar equator than at the poles This differential rotation helps to explain some of the processes occurring on and inside the Sun One of the most notable features of the Sun is the 11 year cycle of activity that it undergoes For several hundred years since about the year 1600 astronomers ha ve been recording the number of sunspots that have been visible on the surface of the Sun Approximately every 11 years sunspots increase in number and complexity on the Sun This 11 year cycle is presently used to help forecast the magnitude of future solar c ycles Sunspots are associated with strong solar magnetic fields A strong field within a sunspot may approach 0 4 tesla or about 4000 gammas This is approximately 6 to 7 percent of the total strength of our Earth s magnetic field During the maximum of the 1 year sunspot cycl
82. de with neutral particles in the atmosphere This phenomeno n is critical for determining ionospheric absorption of radio signals that travel through the iono sphere The 19th and 20th suboptions of the Comprehensive Options menu define the electr on collision frequency model parameters that determine the overall shape of the ele ctron collision frequency models used in PROPLAB We recommend these values are not touched unle ss you are familiar with electron collision frequency profiles and the models used to derive them The equations used to derive the electron collision frequencies are shown below 51 N A Height RefHeight 27 Xmitfreq 10 ColFreq This equation gives the electron collision frequency for one exponential term and therefore corresponds to the collision frequency model containing only one exponential term In the above equation N corresponds to the collision frequency at the height corresponding to RefHeight The frequency of the signal being broadcast into the ionosphere is defined by Xmitfreg and is given in MHz the multiplication by 10 converts MHz to Hz The variable A defines the value of the exponential term that determines the shape of the profile at the altitude RefHeight The equations used to derive the electron collision frequencies with two exponential terms follows below ColFreq N1 exp AI Height RefHeight1 N2 exp A2 Height RefHeight2 27 Xmitfreq 10 In this
83. decided to sacrifice speed in order to improve accuracy and reliability which is what most radio communicators are after anyway And when c ombined with the improved speed and processing power of the modern personal computer ev en speed might not be a problem for many people running state of the art computer systems Here is a small list of the more important parameters PROPLAB considers when determining propagation conditions Entire path analyzed no short cuts Reduction in electron density profiles due to geomagnetic activity Passage through the auroral zone s Winter Anomaly Passage through the polar region Influence of Polar Cap Absorption Equatorial Anomaly Sunset Sunrise Enhancement Degradation modes Influence of solar flares producing short wave fadeouts SWFs Geomagnetic activity Sporadic E Solar zenith angle D region absorption Auroral absorption Date and Time Frequency and transmission power Possible radiowave inter layer guiding modes Sunspot dependencies Varying ground hop absorption Signal multipathing Signal spatial spreading loss Tonospheric focusing and defocusing Signal dependence on magnetic latitude Each of these items may be inter related or dependent on each other in differing ways Determination of signal quality must carefully take these and other parameters and their inter relationships into consideration to produce resul
84. dividing the MUF for a p ath distance of 3 000 kilometers by the critical frequency of the F2 layer at the midpoint of that path Numerically it is defined as M 3000 F2 MUF 3000 foF2 From this if we know the critical F2 layer frequency from an ionogram or stati on report we can determine the MUF for a distance of 3 000 kilometers by multiplying the c ritical F2 layer frequency foF2 by the M factor for the same distance M factors are therefore ratios of two ionospheric quantities Producing global i onospheric maps of these factors can help determine how the MUF and foF2 are related They can also be used together with maps of foF2 to compute MUFs for any part of the world 4 3 Global Maps of Maximum Usable Frequencies Out of all of the global maps produced by PROPLAB these maps will perhaps be the most heavily used For this reason it is important that the maps be interpreted correctly and wisely The following discussion uses the sample maximum usable frequency map in Figure 4 2 This figure was produced for the same date time sunspot number and level of geomagnetic activity as was used in Figure 4 1 They can be directly compared T he similarities are obvious Maximum usable frequencies occur in the same regions as maximum F2 layer frequencies shown in Figure 4 1 Similarly maximum contour gradients occur wher e the sun is either rising or setting The most pronounced and easily defined is the sunrise sector This is becau
85. du ring the ray tracing phase The broadcast coverage maps therefore take this into cons ideration Most antennas that are directional or semi directional are designed to beam most of the radio energy in specific directions As well all antennas broadcast radio energ y at optimum 91 angles of elevation That is most of the radio energy is beamed in preferred directions and angles of elevation To create accurate broadcast maps it is necessary to know 1 The direction or azimuth of the transmission 2 The azimuthal spread of the transmitted signal 3 The useful elevation angle spread of the signal For example let s assume that a directional antenna beams most of its energy in a 45 degree wide azimuthal swath In that swath most of the transmitted signal is directed upw ard at an elevation angle between 4 and 30 degrees These are the only quantities required for PROPLAB to produce a broadcast coverage map PROPLAB produces a coverage map by ray tracing signals through the ionosphere us ing small increments of the azimuthal spread and the elevation spread of the signal In this way it is able to determine the broadcast coverage and quality of signals throughout th e range of the transmitted signal For omni directional antennas you would use an azimuthal spread of 360 degrees from 0 to 360 and an elevation spread of 90 degrees representing a transmitted signa 1 being broadcast in equal intensity in all directions 6 2 Beginn
86. e The ray tracing screen has a large amount of information that can be optionally updated at regular intervals while a ray is being traced This brief section describes t he information that is available on the ray tracing screen 5 1 Location Azimuth Distance of the Transmitter Receiver The first six lines of the left side panel of the ray tracing screen define the geographical positions of the transmitter and receiver It also lists the distance from the transmitter to the receiver in kilometers and the azimuthal angle which should be used to transmit from the transmitter to the receiver This angle is reckoned east of due north For examp le an angle of 90 degrees azimuth represents a position pointing directly to the east An angle of 180 degrees points directly south etc 5 2 UTC Time and Operational Frequency The time and frequency of the ray being traced can be found in the seventh and eight lines of the top left panel of the ray tracing screen The time given here is al ways Universal Time The frequency is always in units of MHz Although only the first four deci mal places of the frequency are printed input frequencies can be much more accurate extendin g down to seven or eight decimal places for increased accuracy 5 3 CUR Lat and CUR Lon Statistics These are valuable statistics that can help you diagnose where various types of signal anomalies or features occur They represent the CURrent latitude and CURrent lon gitude
87. e One profile per se gment produces a small file size less than about 10K bytes Specifying 46 profiles per segment however requires nearly 152K bytes of disk space per file Therefore in the above examples saving 9 segments containing 46 profiles across a 10 degree bearing range using 0 1 degre e bearing steps could result in a profile database being created that approaches 136 8 megabytes 10 degree span 0 1 degree stepping rate x 9 segments x 152K bytes per segment Systems with large hard drives could conceivably handle this but most likely this level of resolution is overkill unless you require highly accurate results with essentially zero inaccuracies It would be far better to reduce the number of segments to 2 or 3 In most cases a 0 1 degree bearing stepping rate is also overkill particularly on shorter distances less than about 10 000 kilometers A stepping rate of between 0 25 and 0 5 degrees should suffice for most instances The amount of disk space required decreases substantially if we save 3 segments containing 46 profiles ac ross a 10 degree bearing range using 0 1 degree bearing steps In this case the size decreases from 136 8 MB to only 9 1 megabytes If the traced rays do not deviate very substantially from the great circle paths the bearing range could even be reduced from 10 degrees to 5 degrees which would cut the required disk space in half again to only 4 56 megabytes In many instances particularly with segments l
88. e the total combined magnetic field strength of all visible spots may exceed the entire strength of our Earth s magnetic field by many times Sunspot groups are often associated with many individual fields which may intertwine and interact with one another Just as a bar magnet has both a north and a south pole sunspots are also polari zed with either positive or negative polarity Most often sunspots appear as bipolar groups or regions where both positive and negative polarities exist When conditions are right these opposite polarity magnetic fields can interact and react with one another to pro duce sudden releases of energy known as solar flares These explosions of magnetic energy can be observed using special filters on optical telescopes known as Hydrogen Alpha fil ters These filters permit the observation of the solar chromosphere where solar flares orig inate The processes involved in the production of solar flares is not yet well known Currently it is believed that flares are related to coronal mass ejections or CMEs CMEs are events on the sun where mass is ejected from the Sun Coronal mass ejections may interfere with the magnetic fields within sunspot regions and trigger solar flares It is presently believed that this may be a dominating role in flare production Previ ously it was believed flares themselves may have been responsible for producing the CMEs How ever it now appears the opposite may be true CMEs may occur before
89. e then select option of the Main Menu to enter the Ray Tracing menu Follow this by selecting suboption 4 Generate Oblique Sounding Io nogram of the Ray Tracing menu You will be asked whether you want to analyze previously generated ionogram data If you have previously collected data you can skip the data collection phase and g o straight to the analysis phase by typing Y Yes at this prompt If you do not want to analyze a previously collected dataset type N No You will now be asked whether you want to append collected data to the existing ionogram database If you previously collected data but want to extend the data to improve the accuracy of the results you will want to select Y to append all collected data to the existing database If this is your first data collection run or if you are beginning to collect data on a different signal path then select N so that any existing data is truncated A paragraph of information is next displayed which should be entirely read It simply explains what is about to happen and how to respond to the following prompts The series of prompts that follow specify details of the transmission the frequ encies to use and step rates The first three prompts define the antenna radiation patter n of the transmitter beginning angle of elevation ending angle of elevation and the step rate to use when ray tracing An omni directional antenna transmits power into space approximately e qually
90. e grid base It is important to remember that if your distance grid is not large enough to en compass the receiver location the dotted green line and the arrow may not be displayed on your screen To resolve this situation increase the distance of the grid using the Options M enu of PROPLAB described earlier 5 17 Pausing and Skipping Traced Rays You can force PROPLAB to pause anytime during the ray tracing phase by pressing the P or Pause key To resume the ray tracing procedure press any other key You can force PROPLAB to skip tracing rays by pressing the S key while individual rays are b eing traced 5 18 Aborting Ray Tracing and Saving Screen Images To abort ray tracing press the ESCape key anytime during the ray tracing proces s Once the ray tracing has been stopped either by forcing it to abort or waiting for it to complete you can save copies of the screen image to a GIF image file by pressing the G key You can save 90 a copy of the screen image to a PostScript compatible file for sending to a laser printer by pressing the P key 5 19 Identifying Regions of Sporadic E Before tracing rays through the ionosphere PROPLAB pre examines the path signal s travel to determine if any regions of sporadic E are crossed If regions of spor adic E are crossed their exact locations are identified on the ray tracing screen as red colored re ctangular cross hatched regions between approximately 103 and 110 kilometers in height
91. e in the light of hydrogen alpha and measuring the size of the flaring area This rating system is composed of a numerical digit and a letter corresponding to the measured optical size of the flare and the brightness of the event respectively Digits are defined as follow and represent the corrected area of the flare in heliospheric square degrees when the flare is at its maximum brightness in H Alp ha S Subflare associated with an area lt 2 0 square degrees 1 Importance 1 2 1 lt area lt 5 1 square degrees 2 Importance 2 5 2 lt area lt 12 4 square degrees 3 Importance 3 12 5 lt area lt 24 7 square degrees 4 Importance 4 area gt 24 8 square degrees The letter which defines the brightness of the flare at the maximum phase of the flare is defined as follows F Faint N Normal B Brilliant All flare locations are given in heliographic longitude which is a done by meas uring the distance of the flaring site from the rotational axis of the solar poles re lative to the limbs of the Sun For example a location of S20E90 refers to a position 20 degrees so uth of the solar rotational equator and directly on the eastern limb A location of N40W00 refers to a position 40 degrees north of the equator and exactly on the central meridian or the longitude line which cuts both through the center of the Sun and through the rotational po les from the northern pole to the southern pole as obser
92. e plasma frequency maps w ith levels of geomagnetic activity above the quiet level about 5 The contouring m ethods employed by PROPLAB may cause incorrect interpolations in the electron density not because the contouring methods are inaccurate or incorrect but because the spatial interval s that must be used to produce the maps may be too large and may leave ambiguities in the gaps that are difficult for the contouring algorithms to accurately interpolate over These regions of p ossible erroneous contours typically occur with higher levels of geomagnetic activity particularl y those associated with major to severe storming A indices above 50 to 100 They appear on the is 0 ionic contour maps as false bubbles in the electron density that occur at regularly spaced intervals These inaccuracies with higher levels of geomagnetic activity will be corrected in fut ure revisions to PROPLAB The iso ionic contours associated with quiet time conditions are more accurate and reliable SECTION 5 SIMPLE RAY TRACING SCREEN The heart of PROPLAB is the engine which traces rays through the ionosphere PROPLAB PRO Version 2 0 has two hearts This section deals only with the simple ray tracing engine It is an entire subprogram in itself and is the file named MODEL EXE This program 84 requires PROPLAB to tell it what to do and how to do it MODEL EXE then performs the requested ray tracing functions and returns the results back to PROPLAB s main m odul
93. e reasons the 2 hop propagation mode is the desired mode for t his antenna path and time of day Figure 8 4 is a similar elevation angle plot for the 5 300 kilometer path from H awaii to Colorado It was constructed using exactly the same data that was used to produce the plot in Figure 8 1 Also compare it with the shorter 3 500 kilometer path in Figure 8 3 and note the differences Perhaps the most pronounced is the observation that lower angles of elevation produce more hops to the destination than for shorter distances As well the range of elevation angles required to support say six modes of propagation decrease as distance inc reases For example a radiation elevation angle pattern of 30 degrees is required to encompass all six possible modes of propagation on the 5 300 kilometer path while the 3 500 kilometer path required a 42 degree elevation angle spread to cover six modes of propagation The elevation a angle spread between individual modes decreases as distances increase 9 xo oo i o 2 What does this all mean It means that a fixed radiation pattern will begin supporting additional modes of propagation Signal Quality Y u i a e N o6 41 54 H RS 2 ae b8 08 Bi IE gs a
94. e recommended O0 kilometer level which defines the transmitter as residing on the surface of the Earth For example PROPLAB PRO V ersion 2 0 sometimes will not properly end ray tracing when the ray s closely approach the receiver location These problems do not appear if the receiver is left on the surface of the Earth However no harm can be done if you play with different receiver heights We will leave the choice of whether or not to play with the receiver height up to you Keep in mind however that adjusting the receiver height may result in some ray tracings that are terminated prematur ely or incorrectly accuracy is not compromised 3 3 18 8 Ray Tracing Rate Steps per hop The comprehensive ray tracing technique traces rays through the ionosphere by in tegrating the rays through specified distances The default distance is 1 kilometer and this forms the basis for the ray tracing rate Larger values force PROPLAB to trace rays through the ionosphere using larger steps while smaller values force PROPLAB to use smaller steps 46 The steps per hop prompt define how many times PROPLAB should attempt to solve the ray tracing problems before giving up The default is 5 000 times which should be enough for most if not all cases If this value is reduced too much PROPLAB may give up trying to solve ray tracing problems before they are solved If during a ray tracing session y ou get an error indicating that PROPLAB reached the iteration l
95. e sunspot number simply type in the number at the prompt To input the 10 7 38 cm solar radio flux value prepend an F for Flux to the number you type An upper or lower case F will work For example to input a sunspot number of 60 type 60 at the prompt To input a solar flux value of 145 type F145 or f145 If you enter a solar flux value PROPLAB immediately converts that value to an equivalent sunspot number That sunspot number is then used in all PROPLAB calcu lations You can obtain the 10 7 cm solar radio flux value from radio stations WWV or WWV H at 18 minutes past each hour on one of the frequencies 2 5 5 10 15 or 20 MHz For greater accuracy it is usually wise to enter the average sunspot number or solar flux v alues for the last week or more The ionosphere reacts more slowly to changes in solar radiation A verage values are therefore usually more reliable than daily values For monthly median results the 12 month mean sunspot number or 12 month mean so lar flux value must be given If you are using the BCAST software and have enabled t he Auto SSN Calculation feature PROPLAB will automatically search the BCAST database for the given date and compute the 12 month mean sunspot number for you when you change dates 3 3 12 Selecting the Number of Allowed Hops This option is used by both of the ray tracing techniques When ray tracing signals between two distant points it may be necessary for the ionosphericall
96. e that the antenna radiation patterns must all have the extension DAT Fai ling to observe this requirement will make PROPLAB blind to the antenna file After we have copied the template file to our newly named antenna radiation patt ern file we can use a standard text editor to modify our new antenna file Within each of the antenna files are specific key words or acronyms that are used by PROPLAB to define re quired parameters Lines that are prepended with an asterisk are treated as comments and are ignored The following acronyms are defined DESCRIPTION Place your description of the antenna on this line limited to 80 characters which includes the word DESCRIPTION which appears on the same line MAXANTENNAGAIN The value placed directly to the right of this acronym defines the maximum gain of the antenna in the direction of MAXGAINAZIMUTH described below The maximum gain given here must be given in units of decibels relative to an isotro pic radiator MAXGAINAZIMUTH_ The maximum gain of the antenna occurs in this direction which is measured in degrees clockwise from true north True north is therefore zero degr ees East is 90 degrees west is 270 degrees etc 120 VGAIN This acronym is used to mark the beginning of the values that describe the radi ation pattern of the antenna in the vertical plane that is in elevation or takeoff angles There must be 90 numerical values that follow the VGAJN acronym and each v
97. ectrons and ions in the magnetosphere and accelerate them These particles follow the magnetic field lines and therefore penetrate mostly into the higher latitudes where the field lines make sharp angles to the surface of the Earth As they penetrate into the ionosphere they reach sufficiently dense regions of the atmosphere to collide with various atmospheric molecules and atoms In the collision the energy released excites the atoms to higher energy states When these atoms drop back toward their more stable energy states they release a photon of light that is unique 10 in color or wavelength for that particular atom It is this light which we see as auroral activity Auroral activity can occur in a variety of colors and patterns Emitted waveleng ths can range from radio to x rays As well as visible aurora there are infrared au rora ultraviolet aurora and x ray aurora Visible aurora can occur in a variety of colors A few of the more important colors observed are green and red at 5577 Angstroms and 6300 Angstrom s respectively produced by excitation of oxygen as well as colors from molecular bands of singly ionized N molecules Most activity appears as greenish blue or greyish colors 2 4 1 Importance to HF Propagation Most radio amateurs and even some professional broadcasters do not understand the significance of the auroral zones in radio propagation The auroral zone is a major region of ionospheric instability and can result
98. ed by high energy cosmic rays which are occasionally observed following strong solar proton flares The D layer is ionized with hard x rays or Lyman Alpha radiation Above the peak of the electron density which usually occurs in the F2 layer the electron density decreases relatively slowly exponentially with altitude This region is known as the Topside of the ionosphere Above the topside lies the protonosphere and the plasmasphere which are not well defined boundaries and stretch for many thousan ds of kilometers in height The ionosphere is strongly dependent on the condition of the geomagnetic field The geomagnetic field cocoons the Earth and stretches out on the dark side of the Earth for millions of kilometers If we could see the magnetic field of the Earth from a distance it would resemble a comet with the Earth as the head The solar wind is a stream of charged particles emanating from the Sun This wind blows at speeds of between 250 and 350 kilometers km per second under relative ly quiet conditions The magnetic field of the Sun is usually pulled out along with the s olar wind When the solar wind reaches the Earth the magnetosphere of the Earth is pulled out along with the solar wind It is this which forms the cometary appearance of our mag netic field When the solar wind reaches the magnetosphere of our Earth our magnetosphere deflects much of the solar wind stream around the Earth The flow of this solar wind over
99. ed at 40N 105W and the receiver was located at 45N 75W to determine the io nospheric electron density profile at the transmitter use the Options Menu to set the rec eiver geographical coordinates to 40N 105W The midpoint obviously therefore must also be 40N 105W which is the desired profile location Similarly to see the profile at the receiver location set the transmitter location equal to the receiver location In this case the transmitter and receiver geographical positions would be set to 45N 75W respectively PROPLAB will plot the electron density profile for any geographical location an y time of day and any date up to an altitude of 1 000 kilometers When the geomagnetic A index is equal to 5 this profile exactly coincides with the output of the International Reference Ionosphere For larger values of geomagnetic activity the electron density prof ile may be altered according to the strength of magnetic activity the geographical position of the profile and other known influencing parameters Electron density profiles provide you with a wealth of information at a glance For example you can determine exactly at what height the maximum electron density occurs You can determine the magnitude of E layer ionization and learn how the profile chan ges from daytime conditions to night time conditions You can examine approximate effects of geomagnetic activity on the profile characteristics and can determine at what a Ititude ionization be
100. ee dimensional grid up to an altitude of 400 km enter 400 at this prompt The Ym parameter defines the thickness of the ionospheric layer being modelled And the foF2 parameter defines the critical frequency of the ionosphere at the HMax altitude The foF2 determines the maximum electron density of the layer through the formula 1 24E 10 x foF2 These parameters should apply to the midpoint of the ray paths in order to produce accurate single hop ray tracings If you are using a three dimensional electron density model these parameters wi Il not be used For novices in ionospheric radio propagation using a three dimensional mo del is highly recommended 3 3 18 18 Ground Gyrofrequency at the Equator The gyrofrequency refers to the number of times charged particles such as electrons and ions spiral around the Earth s magnetic field lines per second The rate with wh ich these particles spin around the magnetic field lines is related to the strength of the Earth s magnetic field The gyrofrequency at the ground and on the equator is used by PROPLAB as a reference in some of its ray tracing operations Altering the given value should only be done by thos e who know what the implications are of doing so In most if not all instances this option will not need to be used 3 3 18 19 Electron Collision Frequency and Profile Shaping Parameters Electron collision frequency profiles are used by PROPLAB to model the frequency with which electrons colli
101. el of geomagnetic activity increases the height of maximum elect ron density also tends to increase The final of these four F2 descriptive lines gives you the ma ximum electron density of the F2 layer for both quiet and dynamic conditions These values will exactly coincide with plotted electron density profiles The next three lines are for Fl layer statistics The first of these three lines defines the critical frequency of the Fl layer if itis present If the F2 layer ionization overlays the F1 layer maximum then the Fl layer critical frequency is invalid and is listed here as zero If the F1 layer maximum is not influenced by the F2 layer then the critical frequency is listed here in MHz The value given will be similar for both quiet and dynamic conditions Geom agnetic activity has a heavier impact on the F2 layer characteristics The maximum elect ron density of the Fl layer is listed last if the Fl layer maximum can be separated from the ower side of the F2 layer If the Fl layer maximum cannot be differentiated the density value li sted on this line is given as zero The next six lines displayed define the characteristics of the E and D regions of the ionosphere three lines for each region The first three lines define the E reg ion critical frequency the E region maximum height of electron density and the associated E region maximum electron density You will notice that the maximum height of electron de nsity of the E region is g
102. enerally fixed at 105 kilometers The three lines devoted to the D region are the same as those for the E region Specifically the first line defines the D layer critical frequency which you will notice is significantly smaller than the critical frequencies of the other layers The final two lines list the height of the maximum D region electron density and the maximum electron density of the D region itself The final four lines of the display show related statistical quantities that are fairly important for determining the ionospheric profile The first line lists the solar zenith angle for 73 the time date and geographical position of the profile The solar zenith angle is the angle of the Sun measured from the zenith straight up It is different from the solar elevation angle which is also listed here in that the solar elevation angle is the angle measu red from the horizon to the Sun in the sky The solar zenith angle is measured from the zenith instead of the horizon Therefore a solar zenith angle of 90 degrees corresponds to a solar elevation angle of zero degrees which represents the position of the sun directly on the horizon 90 deg rees away from the zenith Likewise a solar zenith angle of zero degrees corresponds to a solar elevation angle of 90 degrees and represents the position of the sun directly overhead at the ze nith The second line gives the solar declination angle or the angle above or below the solar eq uator where
103. ens ive ray tracing session it builds a geographical map that includes all of the area covered by the great circle path between the transmitter and receiver It does this by computin g a viewing window through which the results of the ray tracings are presented PROPLAB asks you to type in the geographical latitude and longitude of the left corner of this window either the left top or left bottom corner It then asks you to type in the coordinates of the right corner of the window either right top or right bottom The rectangular window formed from these two corners forms the basis for the viewing window Any geographical details contained within the window are displayed Positive coordinates refer to northern latitudes and western longitudes Negativ e values refer to southern latitudes and eastern longitudes 9 4 Specifying Limits for Collected Data PROPLAB will let you define specific limits to the data in the ray tracing database If a specific ray within the database falls within the acceptable limits you establ ish the ray will be accepted and processed If the ray falls outside of the specified limits PROPLA B will ignore the ray and will not include it in the analysis The items which can be selected as limiting factors are known as filters PROPLAB 116 contains five filters which can be applied to the ray tracing database They are described below The Elevation Angle filter lets you specify the upper and lower limits for
104. equation NJ corresponds to the collision frequency at the height corresponding to RefHeightI and Al is the exponential value that gives this section of the model its shape at RefHeightI N2 is the collision frequency at the height corresponding to RefHeight2 and A2 is the exponential value that gives the model its shape at the height RefHeight2 And as in the previous equation Xmitfreq is the frequency of the signal being transmitted through the atmosphere in MHz With this information in hand the Comprehensive Option menu choices 19 and 2 0 can be appropriately changed to yield the collision frequency profiles you desir e 3 3 18 20 Three Dimensional Data Important Option 21 of the Comprehensive Options menu is a VERY Important section that must be changed every time you change the transmitter receiver locations or ionospher ic profiles Failing to do so will result in inaccurate ray tracings This is the section where you are asked all of the critical questions which dete rmine how PROPLAB builds the ionospheric profiles necessary to support three dimensional c omprehensive ray tracing Before proceeding further make sure you have read and understood Section 3 4 13 Understanding the Generation of Ionospheric Profiles That section will teach you everything you need to know about how PROPLAB generates ionospheric profiles for three dime nsional ray tracing so you will be prepared to properly respond to these important prompts
105. er for both quiet A index of 5 and disturbed o r dynamic times The dynamic value is an estimated critical frequency determined after taking geo magnetic activity magnetic latitude and longitude etc into consideration The next line lists the ionospheric M factor for distances of 3 000 kilometers during quiet conditions The M factor is the ratio between the maximum usable frequency for a distance of 3 000 kilometers and the critical frequency Using this value and the quiet time F2 layer critical freque ncy value you can determine the MUF by multiplying the two values together For example if the cr itical F2 layer frequency was 4 436 MHz and the M factor was 3 13 the MUF for a distance of 3 000 kilometers also written as MUF 3000 would be 4 436 x 3 13 13 885 MHz For distances less than or greater than 3 000 kilometers it is necessary to perform interpola tion or extrapolation on the data However this is unnecessary since the MUF for given distances can be directly determined through the use of the second Main Menu option Compute MUFs The ma ximum F2 layer height is listed on the next line The height where the electron densit y for the F2 layer reaches a maximum is known as the maximum F 2 layer height or hmF2 The value for quiet time and dynamic conditions is given The dynamic value is a quick estimate and may be more accurately determined by producing an electron density plot for the same region You will notice that as the lev
106. ere are no regions between the transmitter and receiver that are devoid of ionospheric info rmation In other words if the number of profiles is sufficient PROPLAB will know everything it needs regardless of where signals may travel between the two points If in Figure 3 2 the ray to ok a path that travelled above the right side X the ionospheric profiles would be able to describe the characteristics of the ionosphere consistently there are no data gaps However if an insufficient number of profiles are generated PROPLAB may begin to see gaps where the ionosp heric profiles do not overlap If traced rays encounter any regions where there are gaps as the one shown in Figure 3 2 it will not be able to accurately compute the ionospheric characteristics 60 This will degrade the accuracy often very seriously of the traced rays It is therefore important that you specify a large enough number of profiles so that gaps are eliminated You can calculate how closely spaced the various ionospheric profiles are in bearing to one another by dividing the bearing range by the number of profiles you are generating For example in the example above we wanted to generate pro files covering a 5 degree spread on either side of the great circle bearing The total bearing spread is therefore 10 degrees 105 degrees 95 degrees 10 degree spread By telling PROPLAB to generate 10 ionospheric profiles over this bearing range PROPLAB will gene
107. ere the ray reverses direction etc The fourth display mode might therefore trace a more course looking ray path This fifth display method smooths out the ray path and displays as much ray path information as possible This is the recommended and preferred three dimensional display mode 3 3 18 7 Transmitter Receiver Height PROPLAB PRO will let you vary the height of the transmitter or the receiver to v alues from 0 kilometers to values as high as 1 000 kilometers However prudence must be exercised when selecting transmitter or receiver heights For example selecting a transmi tter height that is deeply within the ionosphere for instance near the F2 layer maximum of elec tron density several hundred kilometers high may force the transmitter to attempt to transmit signals while it is within the evanescent region Transmissions and ray tracings are not possible if the transmitter is within such a region Such conditions can occur when the transmit ter is within a region of the ionosphere where the critical frequency at the transmitter is ne ar the transmitter frequency By selecting wise transmitter heights it may be possible to simulate the behavior of satellite transmissions It is interesting to see how different the behavior of signals can be if the height of the transmitter is only raised several tens of kilometers The receiver height can also be defined here There are some known problems with adjusting the receiver height above th
108. erhaps of greater importance than the azimuthal stepping rate An elevation angle step rate of 1 degree provides good resolution Smaller stepping rates can be used There is no lower limit to the stepping rate although a stepping rate of zero obviously will not work Keep in mind that if PROPLAB is set up to ray trace with only one ground hop th en only one ground hop will be used when tracing rays through the ionosphere while gener ating broadcast coverage maps Before generating these maps it is usually wise to set up PROPLA B so that it will hop as many times as necessary to reach the destination distance This can be done within the Options Menu discussed earlier 6 3 Computing the Required Data After all of the required inputs have been given PROPLAB begins the process of computing the data required to build the broadcast coverage map The time requir ed to compute all of the data will depend on the values you used and the stepping rates employ ed The time may vary from only a few minutes to many hours depending on the quality of the map you are seeking PROPLAB begins the process of computing the data by ray tracing with the simple ray tracing technique signals through the ionosphere using the starting azimuth and the starting angle 93 of elevation After the first ray has been traced through the ionosphere to the destination at the maximum distance specified PROPLAB increments the elevation angle by the eleva tion angle ste
109. erly if the traced signals are done using this Quick Mod e function For greater speed when using the Quick Mode it is necessary to increase the ray tracing speed of the software see Section 3 3 3 3 3 14 Selecting Plane or Spherical Grids This option is only available while using the simple ray tracing technique PROPLAB uses a spherical ray tracing algorithm regardless of the type of grid that is displayed The examples given in this manual are of the plane grid type That is the surface of the Earth is treated as a flat surface Likewise the ionosphere is displayed as a flat ionosphere even though the algorithms still use a spherical Earth and a spheric al ionosphere This choice of the Options Menu lets you change the type of surface you see In the Plane Grid mode you are given a flat surface In the Spherical Grid mode you are given a spherical surface and a spherical ionosphere to view the traced rays It must be stressed that even if you use the Plane Grid mode all traced rays us e spherical algorithms This is why when using the Plane Grid mode traced rays are gradual ly bent upward as the distance away from the transmitter increases 3 3 15 Selecting Grid Distances and Height Scales This option only applies to rays that are traced using the simple method Use this option to define what distances should be displayed on screen when trac ing rays through the ionosphere All distances whether ground distances or height distan
110. erns and produce broadcast coverage maps based on those patterns However future version s will build on this idea The third input defines the azimuthal step rate PROPLAB should use between the beginning azimuth and the ending azimuth Smaller step rates will result in greater spatial resolution and better accuracy However smaller steps will also require more co mputation time Larger step rates provide quicker computation but less accuracy and the resulting maps will appear more coarse The fourth input informs PROPLAB to ray trace signals no further than the maximu m distance specified If the distance between a transmitter and a receiver is 6 00 0 kilometers it would be wise to specify a value approximately 2 000 kilometers beyond this point so that the coverage does not end at the receiver location but is extended beyond by 2 000 kilometers to better define the characteristics of the transmission at those distances The next three inputs define the characteristics of the transmission in terms of elevation angle For example if a directional antenna transmits most of its power from 4 to 30 degrees in elevation then a beginning angle of elevation of 4 degrees would be specifie d along with an ending angle of 30 degrees The third of these three inputs requires you to spec ify the elevation angle stepping rate Smaller step rates will result in finer spatial resolution but again longer computation times The elevation angle step rate is p
111. es and to generate realistic ionospheric profiles PROPLAB gives you the power to selec t either the URSI or CCIR models PROPLAB uses a corrected version of the most recent International Reference Ionosphere The uncorrected code failed to properly model the F1 region under so me conditions resulting in a discontinuity in the electron density joining the F1 layer region with the lower F2 layer The CCIR and URSI models both produce different results The option to select one of these two models may improve the accuracy of some results For most purposes we recommend the URSI model although under some conditions the CCIR model may prove to be more accurate If one model fails to prove accurate enough for your purposes try the other Consider the electron density profile given in Figure 2 0 This profile was prod uced using the URSI model of the International Reference Ionosphere in PROPLAB The bottomside of the ionosphere below the maximum in electron density consists of five 20 regions The lowest region of significance is the D layer where electron densities begin to rise but are still confined to relatively low levels The E layer exists above the D region where there is usually a small peak in electron density This is also where spor adic E would appear as a sharp increase in electron density near the E region peak Above the E layer exists a valley region which is small near noon but deepens at low solar elevat ions and during t
112. esponded to the declining phase of solar peas EE cycle 22 and as a result was associated with ae HE a relatively low sunspot number of about 30 Jise 18 97 18 78 21 40 Lon 158 20 39 00 Lon 106 00 OBLIQUE SOUNDING IONOGRAM The lower panel of this figure shows fis ss 18 20 you how long it took signals to reach 273 4 Colorado from the Hawaiian transmitter in 145 45 71 56 ma az Fg 8 224 2898785 milliseconds Each plotted block represents Figure 8 1 Oblique Sounding Propagation Delay one traced ray which hit the ground within the Ionogram from Hawaii to Colorado on 30 June 1994 at specified acceptable distance from the receiver Although this figure does not show it the full color display produced by PROPLAB plots each block using a specific color that corresponds to the number of hops that was required for the signal to reach the receiver Since the display in Figure 8 1 is black and white we have grouped those rays which have common numbers of hops At the extreme upper left coroner of the figure a Key exists w hich on full color displays shows you what plotted colors correspond to certain numbers of h ops Notice that there were no signals that arrived at the receiver using a single hop At least two hops were required to traverse the 5 300 kilometer path from Hawaii to Colorado
113. ess than about 8 000 kilometers the number of profiles per segme nt can be reduced substantially without significantly affecting results So selecting wise parameters in suboption 21 of the Comprehensive Options menu will help you control the amount of disk space consumed when developing three dimensi onal profiles This discussion goes into relative detail regarding the way PROPLAB computes 63 ionospheric profiles If you do not understand the method reread this section until you do Failing that experiment with PROPLAB Nothing teaches better than hands on expe rience Keep in mind that PROPLAB PRO contains a useful context sensitive help system If any of the prompts are confusing or seem ambiguous press the F1 key for more detailed desc riptions 3 4 1 4 Understanding the Three Dimensional Grid The three dimensional grid shown to the right was produced during a sample ray tracing session using the comprehensive ray tracing technique It shows one ray entering ne A B AV NARS the ionosphere and splitting into two y SEEN EROS we p p 8 i NNN JS SS l TNN 1 I pi SY f SS SRE EES ORE TESS gt component parts the ordinary and N SRS Sh NS 2 F z a RS SSIBSFRAS MOOS SARS 2 extraordinary parts Unlike the simple ray AS SERS A tracing technique the comprehensive ray SSSR tracing technique draws a straight line from the transmitter to the location where the ray enters the ionosphere The simple
114. ex ray tracing techniques It lets you define the operating frequency of the transm itter in MHz This is a very critical parameter PROPLAB could not function without it for ob vious reasons The operating frequency must be entered in units of megahertz MHz For example a transmitter that is set up to operate on the 40 meter shortwave band would use a frequency of between approximately 7 0 and 7 3 MHz There are no real limits applied to the operating frequency Frequencies in the Medium Frequency bands or frequencies in the VHF bands can be input However please no te that frequencies below about 2 MHz may produce increasingly error prone results with the simple ray tracing method The complex method is better able to accurately handle these wide ranges in frequencies since they use equations which accurately model the physical propert ies and behavior of signals of almost any frequency 3 3 6 Setting the Date Time and Auto Sunspot Number Computation This option applies to both of the ray tracing methods The sixth option of the Options Menu permits you to define the date and time En ter the date in the format YY MM DD and the time in the format HHMM For example 08 Dec ember 1993 at 4 30 pm would be entered using local time as 93 12 08 for the date and 1630 for the time Be sure to enter the time according to how you have setup PROPLAB If local time is used use local time If UTC time is used use Universal time This option als
115. f the antenna relative to an isotropic radiator An isotropic radiator is an antenna that radiates equal amounts of power in all directions It therefore has zero gain be cause it spreads all of its power equally in all directions Antennas that have measurable gain v alues create that gain by concentrating energy flux into specific directions This requires energy to be sacrificed in other radiated directions So antennas with large gains are usually highly directional Antennas with low gains are more omnidirectional The maximum gain value listed is given in units of decibels or dB above those of an isotropic antenna The azimuth of maximum gain describes the direction of the main radiation lobe of the antenna For example an antenna that has a maximum gain at an azimuth of 0 zer o degrees means that the main lobe of the antenna points due north This information is used by PROPLAB to determine gain figures at other azimuth angles during ray tracings 10 2 Displaying the Radiation Pattern After the antenna has been selected PROPLAB asks you if you want to display the radiation pattern of the selected antenna If you answer Y es to this prompt PROPLAB clears the screen and draws two graphical images on screen The image on the left describes the radiation pattern of the antenna as the transmission elevation angle or takeoff angle is increased from 0 degrees to 90 degrees The image on the right describes the radiation pattern of the antenna
116. f the figure and the receiver is at the far right Distances are 4A given at the base of the figure in units of CLA kilometers Height is also given in units of Tt kilometers with height intervals every 50 kilometers labelled This figure therefore shows a cross section of the path between en ae en ee oe Mexico and Australia a ground distance of 3000 over 12 000 kilometers to an altitude of 450 Figure 4 3 Transverse Plasma Frequency Map kilometers The contour lines are plasma frequencies of the ionosphere Plasma frequencies are essentially critical frequ encies for specific heights in the ionosphere For example at the base of the ionosphere the plasm a frequency given in Figure 4 3 is 0 2 MHz This means that a vertically propagated signal b elow 0 2 MHz would be reflected from this base layer while frequencies above 0 2 MHz would p enetrate the ionosphere at that level and travel upward until the plasma frequency increased above the operational frequency The plasma frequency then is the frequency of a signal required to penetrate a specific density of electrons The plasma frequency is related to the electron density through the following equation Density 1 24 x 10 Plasma Freq The plasma frequency is given in MHz and the electron density is in electrons p er cubic meter For example a plasma frequency of 8 MHz is associated wit
117. fectively describe the electron dens ity of the ionosphere for any location around the world and level of solar activity They are of critical importance to PROPLAB because it is the density of electrons in the ionosphere that is responsible for the refraction and reflection of radio signals through the ion osphere 3 3 4 1 Models to use with the Simple Ray Tracing Technique The two available models that can be used with the simple ray tracing technique are known as the URSI and CCIR models Both models are accurate and reliable and are proven performers and produce similar results There is no real preference of one over the other The choice of which model to use is up to you The default has been arbitrarily set to the URSI model 33 3 3 4 2 Models to use with the Complex Ray Tracing Technique The complex ray tracing technique is able to use one of up to six different iono spheric models described as either two dimensional or three dimensional as follows You can select which model to use from Main Menu Option 8 Suboption 18 Choice 4 Model 1 URSI Two Dimensional Model This model is based on the URSI ionospheric model and describes the ionospheric characteristics for a given point on the Earth up to an altitude of 1 000 kilome ters It does not describe ionospheric characteristics in three dimensions and therefore should on ly be used when performing comprehensive single hop ray tracing plots The two dimensional comprehensive ra
118. flected signal will likewise require twice that time An F region reflected signal may take a range of differing times depending on how deeply the signal passes into the ionosphere the frequency used etc In most cases a value of 4 milliseconds will be more than adequate and may produce a more realistic similar to an actual ionogram result than an auto computed value But if you re unsure let the computer do the work for you If you produce an elevation angle related plot you will be asked two final ques tions before the data is finally processed You will be asked to type in the minimum e levation angle used during the ray tracing phase and the maximum elevation angle used during t he ray tracing phase These values determine the grid size After you have answered all of the prompts PROPLAB begins processing the databa se 104 of information contained in CHIRPS OUT You will be told to please wait as the data is processed After the data is processed the results are displayed on screen 8 3 1 The Propagation Delay Plot p Figure 8 1 shows a sample propagation delay plot produced over the path from Hawaii to Colorado The transmitter was located at Hawaii The analysis was produced for June 30 1994 at 15 00 UTC H 20 during geomagnetically quiet conditions This _ fo s2 o a Sanne DURUN f i Signal Quality u i corr
119. from 46 to as much as 414 46 profiles x 9 segments So let s see what happens if we use segmentation in our example At the prompt a sking for the distance along each bearing let s specify a distance of 7 500 kilometers we re splitting the 15 000 kilometer path into two segments of 7 500 kilometers each When prompted for the number of profiles to build along the 7 500 kilometer path we will specify the maximum allowed of 46 The last prompt presented asks you how many segments should be built By specifying a value of 2 PROPLAB will build a total of two segments along each bearing spec ified spanning a total distance of 2 segments x 7 500 kilometers 15 000 kilometers However notice that within each segment we are creating 46 ionospheric profiles thus decreasing the distance between ionospheric profiles from 326 kilometers to 163 kilometers half the distance The resolution has therefore increased by a factor of two By specifying a value of 3 segments instead of two PROPLAB would build three segments each 7 500 kilometers in distance Rays could therefore theoretically be traced out to a distance of 7 500 kilometers x 3 segments 22 500 kilometers However in reality this distance would be limited to 20 000 kilometers because PROPLAB s comprehensive ray tracing engine will not trace beyond this distance 62 By splitting up our 15 000 kilometer path into 9 segments containing 46 profiles each we decrease the spacing between ionos
120. g di stance points have a fairly good chance of passing through the auroral zone particular ly during stronger periods of geomagnetic activity when the auroral zones have expanded in area The ionosphere is capable of transmitting signals approximately 4 000 kilometers in a single hop This is generally known as the maximum one hop distance For greater distances multiple hops are usually required However radio signals frequently travel far beyond this one hop distance during chordal hop propagation or ducting PROPLAB has the power to determine when and how to accomplish communications using these special types of radio propagation modes 2 6 5 Determining Propagation Conditions The determination of ionospheric propagation conditions between two points is not an easy task Conditions can vary widely from minute to minute hour to hour and d ay to day 21 and location to location Many propagation prediction programs use algorithms th at are optimized to improve calculation speed In the process they sacrifice accuracy Others fail to consider important parameters such as the location of the auroral zones and thereby suffer fairly serious inaccuracies particularly on transpolar and high latitude paths Consideration of a wide host of variables is required in order to help secure accuracy and reliab ility And even then the often unpredictable behaviour of the ionosphere may make it difficult to obtain accurate results With PROPLAB we
121. g with contours of maximu m usable frequencies solar zenith angles and any other information that may be helpful to interpret the quality of signals within the broadcast coverage of the transmission PROPLAB does not normally provide a key defining what each of the colors mean in the broadcast coverage map To display the key press the L key on your keyboard The meaning of each of the colors will then be displayed on screen If you are not interested in saving the screen image press any other key and PR OPLAB will either return you to the DOS prompt if you began running ANALYZE from the DOS prompt or will return you back to PROPLAB s Main Menu SECTION 7 COMBINING MAPS Once you have become more familiar with the general functions and operation of PROPLAB you may begin tapping into a few of the more powerful features of PROPL AB such as combining maps PROPLAB is capable of presenting its results using a variety of different map pr ojections The ability to combine maps magnifies the usefulness of the software by many mag nitudes by making it possible to present a great deal of information on screen at once For example during a geomagnetic storm the location of the auroral zones expand equatorward affecting signal paths in the middle latitude regions As well sig nal qualities decrease and multipathing may increase Signals may also be affected by sporadic E Maximum usable frequencies will decrease PROPLAB provides you with
122. gation software do not take the auroral zone degradation into consideration This is unfortunate since many thousands of peo ple who rely on transauroral paths which cross into or through the auroral zone or transpol ar paths for communicating cannot reliably use this propagation software to help determine si gnal quality Moreover since the auroral ovals are offset from the rotational poles of the Earth the location of the auroral zones is continually changing and is difficult to track This is another reason why most propagation programs cannot or fail to account for the auroral zone 11 degradation even though this is the area of the signal path where most signals will be degraded most heavily PROPLAB is based on the results of scientific research and uses proven algorithm s for computing the location of the auroral zones for any time of day and any level o f geomagnetic activity The geomagnetic A Index is the only parameter required aside from the date and time to compute the position of the auroral zones PROPLAB is therefore better equipped to analyze and assess signal degradation through the auroral zones than many other propagation software packages 2 4 2 Auroral Phenomena Auroral activity can produce several different types of phenomena all of which can influence radio communications The enhanced ionization can absorb radio signals This type of phenomenon is known as auroral absorption Sporadic E is common within the au
123. gener ate and press ENTER to begin the process The time required to BEGIN drawing the map depends on the size of the dataset file PATHS OUT PROPLAB must first scan through the data and precompute various qua ntities before the map drawing phase can begin While PROPLAB is busy doing this a box with Processing Data will appear on your screen Be patient After PROPLAB has pre scanned the data the map will be drawn on screen after which the geographical map showing the continents and islands will be superimposed After the map has been drawn you are given ac cess to the commands given in the following section 6 6 Available Commands while Viewing Maps PROPLAB will convert any of the graphical maps displayed into equivalent graphic image files or GIF images by pressing the G key while the map is displayed The sc reen can be converted into a PostScript compatible file that can later be sent to a laser pr inter by pressing the 97 P key Screen images can also be saved to disk in a special format by pressing the S key This latter command permits you to integrate broadcast coverage maps in with other types of maps For example after generating a broadcast coverage map you can use the co ntouring capabilities of PROPLAB to superimpose contours of maximum usable frequencies or critical frequencies etc on the broadcast coverage map Resulting maps may be invaluable and provide for example the broadcast coverage signal quality alon
124. gins in the ionosphere for daytime and nighttime conditions As well if spora dic E is present you can see the spike in electron density that exists in the narrow region where sporadic E exists This is a useful function for determining the overall internal shape of the io nosphere at any given time date or level of geophysical activity for any geographical posi tion 3 4 6 Displaying Ionospheric Profile Statistics The fifth sixth and eighth through eleventh options of the Main Menu will be c overed in detail shortly But first we will examine what the seventh option of the Main Menu does Selecting this option will display ionospheric profile statistics on screen at the midpoint between the transmitter and receiver just as described in the previous section After the ionospheric electron density profile has been computed and adjusted if necessary information describing the properties of the ionosphere are displayed in a textual format on screen At the top of the screen the UTC date and time are given along with the transm itter geographical position given as the Origin The next line lists the sunspot number and geomagnetic A index values that were used to generate the profile statistics as well as the geographical path midpoint position This is the location where the profile stat istics are valid 72 The next four lines define the characteristics of the F2 layer The first line lists the critical frequency of the F2 lay
125. gions known as F1 and F2 The F1 region is the lower of the two Both of these regions are ionized with extreme ultraviolet light EUV The F1 layer is not always present in the ionosphere The F1 Region is ionized primarily with EUV Extreme Ultraviolet The E Region is typically ionized with Soft X Rays D Region ionization occurs with Hard X Rays and Lyman Alpha radiation Often the F2 layer is large This plot shows electron density in units of electrons per cubic meter and i enough to encompass the F1 is a profile often observed during geophysically quiet summer days layer In Figure 2 0 the exact GE Reson location of the F1 region is Poe Pt tt UL Pt tT difficult to discern due to the LY bbbbssas H L ariu H sexy density and spatial extent of ionization in the F2 layer Figure 2 0 Typical Electron Density Profile for a Summer Day The E region of the ionosphere lies between approximately 90 and 140 km and is a fairly dynamic region of the ionosphere Sporadic E or areas of localized and s poradically intense ionization occurs between about 100 and 115 km with a peak near 105 km The E region is ionized by soft x ray solar radiation The D region lies between about 50 and 90 km and contains the D layer as well as another less influential layer known as the C layer or Cosmic Ray layer The latter is ioniz
126. given later in this manual 2 3 Geomagnetic Indices It is useful to quantify the degree of magnetic disturbance observed each day ov er various regions of the Earth or on a global basis Numerous different types of indices have been developed and used over the years Most magnetic observatories determine local indices The local indices are then used to compute the global indices The most popular indices presently used to measure levels of geomagnetic activity are known as the A and K indices Of these PROPLAB only uses the A index although knowledge of how the A index is derived from the K index is useful 2 3 1 The Geomagnetic K Index The K index is a value ranging from 0 to 9 and indicates the magnitude of irregu lar variations occurring with the geomagnetic field over a period of 3 hours using Universal Time UT For example one digit is used to define the level of activity occurring between 0000 and 0300 UTC Another digit is used to describe activity levels between 0300 and 0600 2 Polar Magnetic Substorms Review of Geophys Space Physics 10 page 157 Introduction to Geomagnetism Parkinson W D Scottish Academic Press Ltd Edinburgh 8 UTC and so on throughout the UTC day Since the level of magnetic disturbance is usually higher in the higher latitude regions each observatory is assigned their own rating scale to account for the level of activity observed at each observatory For example an equatorial statio
127. gnetic 100 A index 8 disturbance 8 gamma 8 K index 8 nanotesla 8 nT 8 storm 3 substorm 3 sudden storm commencement 6 Geomagnetic storms 78 GIF 41 75 GIF image 113 GLE 12 Gradients 76 Gray angle 121 Grayline 30 121 Grayline signal 76 Graylines 1 Great circle 20 Great circle paths 1 Grid bounds 59 Grid distance 47 Ground Level Event 12 Group path 65 Gyrofrequency 50 Heights hmD 18 hmE 18 hmF1 18 hmF2 18 Helium 4 High angle rays 23 112 HmF2 79 Hourly MUF 124 Hydrogen 4 Hydrogen Alpha 5 Imaginary 87 Install 25 Integration Adams Moulton 44 Runge Kutta 44 Interaction 3 International Reference Ionosphere 19 Interpolation 61 Ionogram elevation angles 108 optimum angles 108 propagation delay 104 111 Ionogram database 100 Ionograms 99 Ionosonde 99 critical frequency 17 frequency sweep 17 penetration frequency 17 sweep frequency 99 Ionosondes 17 Ionosphere 2 location 2 structure 2 Ionospheric focusing 22 Ionospheric models 32 IRI 19 K index 8 Lateral distance grid 47 Long Paths 32 Low angle rays 112 Lowest Useful Frequency 111 LUF 111 M factor 72 M factors 77 Magnetic disturbance 8 Magnetic field models 42 Magnetosphere 3 appearance 3 Map library 25 Map projections 97 Maximum gain 118 Maximum height 79 Maximum usable frequencies 22 Maximum Usable Frequency 1 3 105 Median 37 Models CCIR 19 URSI 19 Modes 111 Modes of propagation 105 MUF 1 3 98 105 108 125 MUF fading 94 MU
128. h 59 The ionospheric profiles produced by PROPLAB tend to span lateral distances of up to about several hundred kilometers away from the main bearing That is the distan ce between the outermost squares in Figure 3 1 will vary but typically span approximately several hundred kilometers depending on the geometry of the path This is important to realize since it will help you understand whether or not you might need to build other ionospheric profiles parallel to the main bearing Signals that travel through the ionosphere frequently travel paths that do not strictly correspond to the anticipated great circle path Ionospheric tilts effects of the Earth s magnetic field and other anomalies can cause rays to deviate from the great circle path These deviations must be taken into consideration when generating ionospheric profiles This is i mportant because if PROPLAB cannot find an ionospheric profile for a specific part of the ray pat h it will produce a warning indicating that the ray went out of the grid bounds In other words PROPLAB is unable to determine the necessary ionospheric parameters to accurately ray trace signals through the ionosphere This can result in inaccuracies in the traced rays To overcome this difficulty the Comprehensive Options Menu Main Menu 8 Subop tion 18 contains an option option 21 that lets you set up exactly how PROPLAB sh ould create the ionospheric profiles PROPLAB lets you develop ionospheric pr
129. h an electron density of 9 92 x 10 electrons meter That is a frequency of 8 MHz would be reflected from an ionospheric layer when the electron density of that layer increased to 9 92 x 10 electrons per cubic meter Referring to Figure 4 3 above Australia is on the verge of sunrise while Mexico is experiencing conditions at approximately noon Concentrate on the far right side of the map nearest Australia As you travel from right Australia to left toward Mexico the electron density of the D and E regions begins increasing The contours illustrate this There is also an attendant rapid increase in the electron density associated with sunrise in the F region of the ionosphere above 150 km This region of the ionosphere is tilted A non tilted ionosphere would be one where the contours are horizontal and flat In this case there is considerable tilt as you travel from Australia toward Mexico or visa versa particularly in the distance range between 5 000 and 10 000 kilometers from Mexico These are areas where non great circle paths may be observed Figure 4 3 also shows what happens as signals pass through the equatorial region As was mentioned earlier the height of maximum electron density in the ionosphere increases as the 83 magnetic equator is approached This is clearly visible in the transverse plasma frequency map as an increase in the height of the iso ionic contours from Mexico at zero km s to about 5 000 kilometers
130. hanging circumstances result in more accurate results 2 4 The Auroral Zones The auroral zones can be defined as those areas of the Earth where visible aurora occurs overhead They typically occur within an oval shaped ring centered approx imately on the north and sound magnetic poles Two zones of aurorae are therefore visible on the Earth one near the north magnetic pole and the other near the south magnetic pole Since the northern magnetic pole lies closest to North America Canadian regions are well placed for observing periods of auroral activity In the northern hemisphere this activity is known to the public as the northern lights or the aurora borealis In the southern hemisp here it is known as the aurora australis The Solar Terrestrial Dispatch has developed a Professional Dynamic Auroral Oval Simulator for IBM compatible PC computers running MSDOS which will explicitly delineate the location of the auroral ovals for any given hour and level of geomagnetic activity It will also show you where in the sky to look for aurorae and will simulate the intens ity and spatial extent of activity visible from any position on the Earth For more information write us regarding this software package Auroral activity is the result of atmospheric atoms and molecules being excited by energetic electrons and ions beamed into the ionosphere During geomagnetic subs torming for example processes beyond the scope of this manual excite el
131. haracter of those signals t hat never reach you you can specify Y at this prompt to accept all signals that reach the receiver whether they are useless or not The last major prompt asks you for the type of analysis you want to carry out an analysis of propagation delays by pressing P or an analysis of elevation angles by pressing E The propagation delay analysis shows you how long it takes the received signals to r each the receiver after they leave the transmitting antenna The results given by this analysis are far reaching and exceptionally useful The elevation angle analysis shows you what transmission e levation angle was used for each of the signals that were received by the receiving antenna This plot is likewise a very useful tool and can give you a great deal of insight into optim um transmission angles We will discuss the features of these plots shortly If you produce a propagation delay plot you will be asked if you want the compu ter to automatically compute the resolution of the display or if you want to control t his yourself Press ENTER or type Y to have the computer do this for you automatically To set the resolution manually you are asked for one final piece of information how many millisecond s should the grid display A single hop E region reflected signal requires a little more than approximately 3 milliseconds to travel from the transmitter to the ionosphere and back to the ground A two hop E region re
132. hat occurs on the data to make it fit into the allocated map properly They can and should be ignored Alternatively you can filter out th ese island regions by specifying a minimum contour value that is close to zero but is slightly positive ex 0 1 or 0 2 This will help clean up the display if you find it too messy 9 6 Database Offset Value The broadcast mapping software is only able to handle up to 2 000 datapoints at a time That is if you have traced more than 2 000 rays during a previous ray tracing s ession only the first 2 000 points will be used By specifying filter limits you can increase this number almost indefinitely by ignoring rays with certain undesirable characteristics However there is another way around this limitation The last question prompted by the mapping software asks you to specify an offset into the database Normally the offset is set at zero which means that PROPLAB will begin processing data at the very beginning of the database By increasing this offset value you instruct PROPLAB to begin skipping records in the database If you have for example 300 0 rays in the 117 database each ray occupies one record then specifying an offset value of 1000 would force PROPLAB to skip the first 1 000 records in the database It would therefore begi n accepting data for analysis beginning with the 1 000th ray record Use this offset to analyze sections of your database that might not have been an alyzed prev
133. he increase in the MUF to about 23 5 MHz made possible by the ability of the ionosphere to return single hop signals from a portion of the ionosphere that is more 9 i 2 i Loi DUDAWNE x D a 2 Signal Quality W u i a e N o6 14 66 gt H RR iaaa me Ia kes intensely ionized At 05 00 UTC on 30 June 14 18 rng ae 19 94 eet Hawaii is almost directly on the sunset 13 70 a ine Dod sar oe 13 46 tt H eT L z grayline As the signal travels from Hawaii to ap reo ia EEF Eee kez 36N 126W towards Colorado the electron ETA un gt i eao at Et ines z 2 Hops iE 3 density in the ionosphere will decrease H mal a 45 3 x aos E JH eHe ae iit k3 because the signal is moving into deeper areas E J 4T F AlN a a i Horo as ri gt e ea Hidi e PA ao ars 0o of the night The 5 300 kilometer path Figure 8 2 Propagation Delay Ionogram from Hawaii to requires two hops The first hop would have 36N 126W made from the same data as Figure 8 1 by been associated with an MUF near 23 MHz chank ine Me distance dram SOD Ie TA AARO ki but the second hop would be associated with an MUF closer to 17 5 MHz Higher frequency signals would penetrate the ionosphere d
134. he night Above the valley is an intermediate region that bridges the ga p between the valley and the F layer Depending on season time of day etc there may or may not be an F1 region present Detection of the Fl region is usually more difficult because of F2 region dominance PROPLAB will let you produce ionospheric electron density profiles for any region of the Earth and any level of geophysical activity 2 6 4 Propagation Paths Radio signals always try to travel the shortest distance between two points On a sphere such as the Earth which is a close enough approximation the shortest distance between two points is known as the great circle distance You can determine the great circle path between any two points on a globe by stretching a taught string between the two points For east west northern hemisphere points you will notice that the string appears to form an arc that arcs toward the northern pole before reaching the destination Likewise an east west great circle path in the southern hemisphere travels toward the southern pole be fore arcing back toward the destination On north south paths the great circle lies on one of the longitude meridians Longitudes are therefore great circles because their planes cut through the center of the Earth Latitude circles do not have planes which cut through the center of the Earth and are therefore not great circles Radio signals that are transmitted between two east west middle latitude lon
135. he only propagation software in the world for IBM or compatible personal computers that will show you the precise behavior of radio s ignals as they travel through the ionosphere It effectively simulates radio transmissions into the ionosphere with a high degree of accuracy by using sophisticated ionospheric ray tracing techniques It is hoped this manual will help teach the reader how to use and interpret the numerous available features of PROPLAB as well as how to better understand the i onosphere This manual may therefore serve as both a tutor and a reference Most if not all of the illustrations given in this manual were generated by the PROPLAB PRO softwa re Honospheric Radio Kenneth Davies 1990 Peter Peregrinus Ltd The Propagation of Radio Waves K G Budden 1985 Cambridge University Press SECTION 2 BACKGROUND 2 1 The Ionosphere and magnetosphere The ionosphere is that region of our upper atmosphere which lies between about 5 0 km and several Earth radii For our purposes the ionosphere is defined as the region between about 50 km and 1000 km This is the area where the major effects of signal refr action take place It also encompasses almost all of the phenomena which can affect radio communications Figure 2 0 below illustrates the structure of the ionosphere on a quiet summer day The peak electron density of the ionosphere usually occurs in the F region of the ionosphere The F region is divided into two re
136. he same procedure applies to these values as applied to the VGAIN values Again all values must be relative to the maximum gain of the transmitter as stated beside the acronym MAXANTENNAGAIN Negative values are therefore impossible for the same reason as above After you have modified the antenna file save it to disk and run PROPLAB Then select the antenna from the antenna menu Main Menu Option 10 and view the radiation pattern to make sure it is correct If you can t find your antenna in the antenna menu you probably saved your antenna file to the wrong directory Make sure all antenna files are saved in the ANTENNAS subdirectory PROPLAB will not search elsewhere for them Also make certain your antenna file has the extension DAT ex SHRTWIRE DAT PROPLAB will igno re files that do not have this extension SECTION 11 REAL TIME MAPS PROPLAB PRO Version 2 0 comes equipped with an exceptionally powerful new functi on that will produce real time maps on your computer You can even display the current local times for any number of cities around the world all updated at user specified interva ls 121 This function gives amateurs radio operators for example the ability to speak with friends on the radio while at the same time looking at real time maps of ionospheric con ditions grayline locations and local times for cities around the world including your friends lo cal time This is a significantly useful tool For this
137. hich are heavily color coordinated Consult your printer manual for all of the initialization string codes which sho uld be used in the printer control file Each printer usually differs which is one reason why a printer control file is used It permits essentially universal compatibility with printers If you have a laser printer don t use the H command as this is optimized only for dot matrix printers For later printers create a P ostScript version of the graphic screen After it has been saved to a PostScript file containing the extension PS e xit to DOS and copy the PostScript file to your laser printer 3 3 Setting the Required Parameters The eighth choice of the main menu is an Options Menu This is where you setup most of the parameters required to run PROPLAB It is where you define the opera ting frequency transmitter power date and time location of the transmitter and rec eiver sunspot number etc The options in this section should be adjusted to fit your specific ations before you perform any of the major functions of PROPLAB such as ray tracing or determ ining MUFs etc Here we will briefly describe the available options 3 3 1 Setting the Transmitter Receiver Locations and Time Zones PROPLAB requires the geographical position of the transmitter and receiver in or der to work The first two options of the Options Menu let you change these paramete rs to fit your needs 29 Geographical positions should be en
138. hird option of the Options Menu This value is preset to 10 which is a nice round arbitrary figure that pr ovides decent speed of operation and accuracy for systems that are both equipped with and with out math coprocessors Lower values cause PROPLAB to trace rays through the ionosphere in smaller increments This may increase the accuracy of the results slightly but will also slow down the speed of operation by increasing the number of required calculations Likewise larger values will speed up traced rays by tracing through the ionosphere in larger ste ps However the results will become less accurate as larger ray tracing speed values are used This is particularly true for signals that must pass through regions of sporadic E wher e density increases rapidly over a short height interval A judicious choice of ray tracin g speed is 32 required when considering the effects of sporadic E on traced rays If a value too large is used the signal may completely step over the region containing sporadic E For this reason smaller values of around or less than 10 are recommended when taking sporadic E into consideration You can also define the type of path you want traced from within this option Th is only applies to the simple ray tracing technique To use Long Paths select L To use Short Paths select S The complex ray tracing method cannot trace rays using long paths It always traces rays using the shortest distance between the tran
139. ht strikes a mirror at a 90 degree angle perpendicular to the surface of the mirror the reflected ray will completely reverse direction and bounce right back along the same path that the incoming ray took This is why it is possible to see yourself in a mirror This same principle applies to almost all polished surfaces whether opaque or n ot For example it is possible to see your reflection in a store window yet people inside the store can look out through the window Reflected rays are well behaved and easily computed Refracted rays are more difficult Refraction in a practical sense is the process of bending something Although light travels in a straight line light can be bent if it travels through material of varying densities For example if you take a pencil and stick it into a bowl of water at an angle the pencil will appear to bend at the boundary between the air and the water even though in rea lity the pencil is solid and straight Likewise a ray of light which strikes water at an angle will appear to change direction or bend at the boundary between the air and the water The reason the pencil appears to bend is because the light at the boundary between the air and the water changes direction or refracts In reality a ray which strikes a surface which is not totally opaque may both r eflect and refract the ray Consider for example what happens with the bowl of water If the surface of the water is undisturbed it is p
140. ial conditions where the ionosphere is particularly stable high angle rays can result in communications at frequencies above the MUF Let s now go back to Figure 2 5 The maximum usable frequency in this example li es just outside of the skip distance near the location where the arrow points at the bottom of the figure MUFs occur in regions where ionospheric focusing is usually strongest In this example it can be seen that the elevation angle that coincides with the maximum usable frequency does not coincide with the elevation angle correspondin g to the penetration frequency The penetration frequency is slightly higher than the max imum usable frequency To help solidify the meaning of eee DERRE iE 5 0000 0000 7 maximum usable frequency consider the final example given in Figure 2 7 The same parameters were used in this figure as those that were used to produce Figure 2 5 except that a fixed angle of elevation of 9 degrees is used while varying the frequency The location denoted by the arrow at the bottom of both of these figures is the location of the MUF In these examples the MUF is approximately 13 2 MHz Figure 2 7 sweeps the frequency from 10 MHz to 14 MHz in steps of 0 5 MHz or 7003 2000 gt 500 KHz and shows that for an elevation Figure 2 7 Frequency Sweep showing concept of MUF angle of 9 degrees the maximum usable and penetration frequency frequency is approximately 13 0 MHz corresponding to the ra
141. ictable nature of sporadic E it is impossible to determine for certain what level of sporadic E exists at a specific period of time The only definite way to measure the critical frequencies of sporadic E are with vertical ionosondes But such in strumentation is usually out of reach of most amateurs and may require special class licenses to operate on the HF bands since they can create interference with other broadcasters Many ionospheric sounding stations report critical sporadic E frequencies to the World Warning Agency WWA in Boulder Colorado The WWA then provides this information in a coded format to other organizations Part of the responsibility of the Solar Ter restrial Dispatch is to decode this data and disseminate it to the general public researchers and other scientific organizations The daily summary of ionospheric data can be obtained from the ST D computer BBS at 403 756 3008 in the Ionospheric Data submenu Old data is archived into files having the format iono xxx zip where xxx is replaced with the first three letters of the month desired ex iono nov zip These archived files are available in the directories 69 pub solar 1991 pub solar 1992 etc These daily ionospheric data reports co ntain critical F2 layer frequencies critical sporadic E frequencies and much more for many stati ons around the world Using these reports it may be possible to determine exactly what level o f sporadic E may have been influen
142. ifferentiated from the MUF contours Many maps of different types can therefore be superimposed on one another to provide a wealth of information on one screen SECTION 8 ALL BAND SPECTRUM ANALYSIS Using the Simple Ray Tracing Technique PROPLAB comes with a powerful new function to produce oblique sounding ionograms giving you the ability to analyze propagation characteristics and conditions thr oughout a wide range of frequencies This function is imbedded within the Simple Ray Tracing su bmenu and can be found by selecting Main Menu option 1 S submenu option 4 The followin g discussion pertains strictly to this function 99 8 1 What is an Oblique Sounding Ionogram Ionograms are produced using an instrument known as an ionosonde Ionosondes are simply special radio transceivers radio transmitter receiver combination desig ned to transmit signals into the ionosphere and measure the character of the energy that is returned from the ionosphere In this respect they are similar to radar guns We established earlier that signals which are propagated into the ionosphere are reflected according to the density of electrons present in the ionosphere Regions of high ionospheric electron density are capable of returning higher frequencies This behaviour is the foundation upon which we are able to probe the ionosphere Ionosondes probe into the ionosphere by using a sweep frequency transmitter That is the frequency of the transmission
143. iles This is a very important question that you must answer properly But before you can give a qualified answer you must bette r understand 57 how and why PROPLAB PRO uses electron density profiles The next section Sectio n 3 4 1 3 discusses this in detail Please read that section next before proceeding The rest of this section should then be easily understood If you choose to use the existing electron density profiles PROPLAB will immedi ately load up the ray tracing engine and begin ray tracing the signals through the ion osphere using the existing set of ionospheric profiles If you choose not to use the existing electron density profiles PROPLAB asks you whether or not to delete the existing profiles from t he PROFDATA subdirectory before building the new profiles If you need to increase the resol ution of the profiles ex decrease the steps between successive profile azimuths select n o at this prompt so PROPLAB will not delete the existing profiles By specifying n o PROPLAB asks you whether or not it should overwrite existing profiles if it encounters any If you instruct PROPLAB not to overwrite profiles the speed of the profile generating phase will increase since any existing profiles that match those that are requesting to be built will be skipped not overwritten If you want to make sure that all of the profiles are fresh and in tact instruct PROPLAB to overwrite any profiles that already exist Please note that
144. imit increase this value in step s of approximately 500 to 1000 If this value is left at 5 000 PROPLAB should handle almost all in stances without prematurely giving up 3 3 18 9 Magnetic Pole Lat Lon This suboption lets you define the exact location of the Earth s northern geomagnetic pole It is only used if you are using a ray tracing model that requires the Earth s magnetic field as input Positive values represent northern latitudes and western longitudes Negative values represent southern latitudes and eastern longitudes Results may differ consider ably from reality if the southern magnetic pole or other geographical locations are used to repres ent the magnetic pole 3 3 18 10 Maximum Minimum Ray Tracing Step Length This option lets you change the maximum and minimum allowed step lengths during comprehensive ray tracing When PROPLAB is tracing through regions which are rel atively free of refractive effects as occurs for example when ray tracing below the ionosphere it is permitted to increase the stepping length to the specified maximum value When PROPLAB is tracing rays through regions of the ionosphere where small increments in distance result in substantial changes in refractive indices PROPLAB is permitted to decrease the stepping length to the specified minimum value in order to properly integrate the equations through the rapidly changing regions of the ionosphere The defaults of 10 km and 0 01 km for the ma ximum and
145. in all directions We only consider the vertical elevation above the horizon since the antenna is assumed to already be pointing at an optimal azimuthal location toward the recei ver An omni directional transmitter would have a starting elevation angle of 0 0 degrees and an ending angle of elevation of say 89 degrees Avoid using ending elevation angles of 90 degrees as the near vertical propagation of low frequency signals may result in lengthy computation times during this Phase Values close to 90 degrees can be used instead such as 89 0 or 89 5 After inp utting the starting and ending elevation angles of the transmission you are prompted for t he elevation angle step rate Since PROPLAB traces rays through the ionosphere from the starting el evation angle to the ending elevation angle a step rate must be specified so that PROPLAB kno ws how to progress from the starting to ending angles The lower the step rate the greater the resulting accuracy will be but the longer the computation time will also be A step rate of 0 5 degrees 101 to 1 0 degree yields reasonable accuracy The prompt asking to Update the Screen Statistics at what rate does not affect the accuracy of the results but will affect the speed that PROPLAB produces results This prompt determines how frequently PROPLAB should update the ray tracing screen statistics Large values in excess of say 200 to 300 will speed up the ray tracing slightly by updating the statistics
146. in significant signal degradation affecti ng frequencies from the ELF to the VHF UHF bands Failure to consider this region of ionospheri c instability can result in significantly flawed and inaccurate propagation predic tions and circuit analyses The auroral zones are regions where electrons penetrate and deposit energy into the ionosphere Electrons with energy levels between approximately 1 and about 20 or 30 keV are responsible for most of the ionization above 100 km Of this ionization a g ood portion of the total ionization occurs at the lower levels of the ionosphere near 100 km although significant instabilities can exist above this level as well On an average quiet day the auroral zone is situated near a geomagnetic latitud e of 67 degrees However the auroral zone is a dynamic region capable of rapid expansion and intensification during substorm periods Equatorward migration of the auroral ov als is a common feature of auroral substorms During enhanced periods of geomagnetic acti vity the auroral zone expands equatorward to encompass areas of the world which are not p art of the quiet time auroral zone This is one reason why some transatlantic circuits may experience complete signal loss during geomagnetic storms while others are capable of condu cting reasonable communications The quality of the signal depends to a fairly large extent on the position and level of activity of the auroral zones For these reasons most radio propa
147. in that file Edit it with a standard word processor or text editor to meet 28 your printers requirements This printer control file is only intended for dot m atrix printers If you have a laser printer PostScript you should be using the command to cre ate a PostScript image file Do this by pressing P at any of the graphics screens presented by PROPLAB Then exit to DOS and send the saved PostScript file which contains the extension PS to your printer At any of the graphic screens presented by PROPLAB except the Broadcast Coverag e Map screens pressing H short for Hard copy will cause PROPLAB to begin sen ding the contents of the current graphic screen to your dot matrix printer If you fail to modify the printer control file PROPLAB PTR correctly for your printer you may see garbage printed instead of an accurate rendition of the gra phic display The initialization strings are of greatest importance Make certain that the ini tialization strings contain if needed by your printer the correct size of the printed lines and that the given size matches the LOCKSIZE parameter read the file PROPLAB PTR for more information Failure to do this will cause improper printer operation Those wi th laser printers may find it easier to simply convert the graphic screens to a PostScrip t compatible format by pressing P Postscript at any of the graphic screens This is the only way to reproduce the broadcast coverage map screens w
148. in the CITYTIME D AT file so that they are also displayed on screen when you do real time mapping simply use your text editor to copy the lines containing the desired cities from the PROPLAB LOC file to the CITYTIME DAT file Since these are both text files modifying them or adding cit ies to them is as simple as loading your text editor and changing them To display all of the local times associated with the locations listed in the geographical database use the DOS copy command to copy the PROPLAB LOC file to the CITYTIM E DAT file For example type copy PROPLAB LOC CITYTIME DAT This will place a copy of the geographical database in the CITY TIME DAT file Now every time you produce real time maps all of the local times for each of the locations defined in the PROPLAB LOC file will be displayed on screen and updated at the intervals you specify 123 A prompt presented by PROPLAB in the real time mapping function asks you if you want to display the names of cities on screen as well as their local times If you specify Y es here PROPLAB will display the names of the cities above the dot which identifies the location for the city The local time for that city is then displayed below the identifying dot If you have a large number of cities to display you might not want to include the names because fo r large numbers of cities the screen can quickly become saturated with city names that overlap one another For a smaller number of cities
149. ine below it represents an estimated low limit for useful frequencies From about 11 00 UTC to 13 00 UTC the distance or range of freque ncies between the FOT line and the thin line decreases until they finally cross one another This indicates a narrowing of the range of most useful frequencies Between about 13 00 UTC and 21 00 UTC the FOT line represents the lower limit of optimum frequencies while t he thin line represents the upper limit After they cross again shortly after 21 00 UTC the thin line becomes the lower limit and the FOT line becomes the upper limit In these ways users c an determine the most reliable range of frequencies at a given time during the day In addition to the sunspot number or solar flux time of day and the coordinat es of the transmitter and receiver PROPLAB also includes effects of enhanced geomagnetic activity through the geomagnetic A index figure A sample map given for the same path as the one above is presented below The difference is the geomagnetic A index is 100 seve re storm conditions Notice the dramatic reduction in the MUF and how this effectively narrows the range of usable frequencies The time between approximately 13 00 UTC and 15 00 UTC shows a region where the 126 HOURLY MAXIMUM USABLE FREQUENCIES F2 layer MUF is below the E layer MUF Bio This is significant because it shows that 28 0 2o signals that penetrate the E layer will also 2a o penetrate the F2 layer and be lost into sp
150. ing Inputs The first prompt presented by PROPLAB is a question asking for which type of Bro adcast Coverage Map to generate To construct broadcast coverage maps from data collect ed using the simple ray tracing technique select S at this prompt To use the comprehensive broadcast coverage mapping system which uses the comprehensive ray tracing technique se lect C Before any other inputs are requested PROPLAB asks you if you want to use a previously generated dataset If you have previously computed a broadcast covera ge map and simply want to view the results of the ray tracings you would select Y es at this prompt If you respond N o PROPLAB will delete any old pre computed datasets and begin compil ing a new one All broadcast coverage results are stored in the file PATHS OUT If you want to save a broadcast coverage map dataset rename this file to something else so that it is not truncated and overwritten The first input required is the beginning azimuth of the transmission The second input required is the ending azimuth of the transmission These two inputs define the limits of the antenna radiation pattern For antennas which are semi directional ex those which transmit most of their power in one direction and smaller amounts of power in the 92 other directions choose those directions where most of the energy is directed The current version of PROPLAB does not provide you with the ability to define radiation patt
151. ions 2 6 6 Skip Distance and Maximum Usable Frequency 2 7 Ray Tracing Techniques lt 5 496 20s be oe EHO E SEN ERED ES SECTION 2 PROPLAB erore 3 git eae ee BAe o ele ahs Rye As BAe amp is 3 1 Installation of PROPLAB 20 0 0 2 ees 3 2 Running PROPLAB Changing Colors and Setting Up the Printer 3 3 Setting the Required Parameters 0 00000 eeeee 3 3 1 Setting the Transmitter Receiver Locations and Time Zones 3 3 2 Graphically Setup Transmitter Receiver Locations 3 3 3 Ray Tracing Speed Path Type and Termination Mode 3 3 4 Choosing Ionospheric Models URSI or CCIR 3 3 4 1 Models to use with the Simple Ray Tracing Technique entirar S50 340 8 6 OR IGA Ree TERS 3 3 4 2 Models to use with the Complex Ray Tracing Technique 3 hee see Roe Ae wed PORE a E 3 3 4 3 The Right Model to Use 3 3 5 Setting the Operating Frequency 4 3 3 6 Setting the Date Time and Auto Sunspot Number Computation 5 sw a RFA ERG RA SE OLERA ES AS 3 3 7 Setting the Transmitter Power 00050 3 3 8 Setting Ranges and Steps 20 2 0 eee eee ee 3 3 9 Selecting Local or Universal Time 3 3 10 Setting the Geomagnetic A Index 3 3 11 Setting the Sunspot Number or Solar Flux 3 3 12 Selecting the Number of Allowed Hops 3 3 13
152. iously due to the size of your database 9 7 The Plotted Map After all of the prompts have been answered PROPLAB begins reading in the datab ase and filtering out those values which do not fit within the specified limits The default limits should be more than sufficient to accept all of the data in the database That is if you do not specify or change any of the limits PROPLAB will use the entire database After the data has been read it is processed and the appropriate contouring mat rices are established Following this which will take some time depending on the resolution level you have selected and the speed of your computer PROPLAB will clear your screen and beg in plotting any geographical features that exist within the viewing window This phase may also require a little bit of time since PROPLAB references the high resolution geographical dat abase of more than 100 000 coordinate pairs to create the geographical map You can force PROP LAB to stop plotting the geographical features by pressing the ESCape key once during this p hase PROPLAB now traces the great circle path from the transmitter to the receiver T his is a useful reference line that can help determine whether or not signals are follo wing or deviating from the anticipated great circle path and by how much The next step PROPLAB takes is to begin the contouring phase if the map require s contouring For maps which only plot the geographical locations where rays h
153. is function is to determine what angle of elevation to use for signals to reach a specific distant location Most propagation programs give you a single transmission angle of elevation for signals to reach destinations Unfortunately as you will discover while using PROPLAB those angles of elevation can often be significantly in error be cause the algorithms used are empirical in nature and attempt to lump together all ray paths In other words those programs do not consider individual ray paths in the ionosphere and as a result must estimate elevation angles The method employed by PROPLAB is one of the most acc urate methods available and should yield good results under most conditions Because P ROPLAB traces each ray individually through a dynamic ionosphere the angle of elevation required to reach a specific distant destination can be accurately pinned down Simply sweep a range of 55 elevation angles and look for rays that strike close to the desired destination PROPLAB uses the arrow at the bottom of the screen in the distance scale as has been shown in previous Figures along with a vertical dotted green colored line to mark the exact location of the destination point It is therefore easy to determine the proximi ty of traced rays to the destination by simply comparing the location of the rays with the arrow or green dotted line Sweeping frequencies is as useful as sweeping elevation angles Sweeping frequen cies can tell you a gre
154. is oc curring Best signal coverage occurs generally to the south and covers most of South America t o some degree Signals should also reach Hawaii but with only fair signal quality Paths more directly toward the east and west and northeast northwest become poor rapidly On the frequenc y used to produce this map signals penetrate the ionosphere or are lost through other pro cesses fairly rapidly with distance Best signal coverage although not necessarily the best signal quality coverage occurs toward the south As well most of the continental U S is unable to receive the transmission due to the size of the skip zone indicated However Florida and a portion of the ex treme southeastern and eastern coastal states would receive an exceptionally good sign al since these regions are just outside of the skip zone and are in the regions of high signal quality as are portions of the extreme northwestern states northern British Columbia and nort hwestern Canada Extreme southeastern and eastern regions of the U S that are almost directly on the skip zone boundary would also likely experience potentially severe fading caused by the cl ose proxim
155. is refracted when it penetrates into our denser atmosphere The same process applies to refraction of radio waves within the ion osphere Radio waves are simply low frequency or long wavelength rays of light When a ray penetrates into the ionosphere the electron density increases rapidl y with height until a maximum is reached approximately 250 to 400 km high As the ray p enetrates more deeply into the ionosphere the increased electron density causes the ray to begin refracting The degree of refraction which occurs depends on the maximum electro n density observed as the ray travels through the ionosphere and the frequency or wavele ngth of the ray Lower frequency or longer wavelengths encounter greater refraction than rays with higher frequencies or smaller wavelengths as FAL a0 Consider the example given in as Figure 2 2 where a radio ray with a frequency of 10 MHz is transmitted through CoR Anaic i sre vsti 008 the ionosphere with a starting transmission elevation angle of 0 degrees This corresponds to the ray which propagates the farthest and is directed toward the horizon Details regarding the contents of this figure are given later in this manual All of the values at the bottom of the figure from left to right are ground distances from the origin at the left side of the screen in Ina 200 Lab kilometers The numbers from top to Figure 2 2 Rays Traced through the Ionosphere bottom on the left side of the figure
156. is swept or increased from low frequencies to high frequencies As the signals from the low frequencies penetrate the ionosphere t hey are reflected back to the transmitter and the receiver picks up these reflected transmissions Since low frequencies can be reflected by relatively low electron densities these low fre quency reflections give us an idea of the content of the lower portion of the ionosphere As the frequency of the transmitter increases the signals penetrate deeper into the ionosphere before t hey are returned to the Earth Eventually as the frequency continues to increase the frequency will exceed the critical frequency of the F2 layer and never return to the Earth By carefully t racking all received signals with the receiver as the transmitter frequency is increased we can build a picture of the ionosphere up to the maximum density of the F2 layer These pictures are known as ionograms and can give you a wealth of information regarding the state of the i onosphere Oblique ionograms are simply pictures of the ionosphere produced by measuring all of the received energy propagated from a transmitter some distance away as the fre quency of the transmitter is swept from low to high frequencies Using oblique ionograms you can easily determine optimum working frequencies maximum usable frequencies minimum usable frequencies the extent of signal multipathing present on specific frequencies and much more We will discuss the pro
157. is the sixth line down from the top line and is labelled Ne which is short for electron density This value is given in scientific notation and represents the electron density per cubic meter Since there is only room for one digit in the exponent and since the electron density frequently exceeds values that require two digits for the expon ent PROPLAB converts the exponent into a value from 0 to 9 as usual For exponents greater t han 9 letters are used to define the exponent The letter A represents 10 the letter B repres ents an exponent of 11 and the letter C represents the exponent 12 For example the reported electron density of 4 6E B would be interpreted to read 4 6E 11 electrons per cubic meter 5 7 Estimated Signal Strength Bar Graph PROPLAB PRO Version 2 0 replaces the signal spreading loss bar graph with this n ew estimated signal strength bar graph This graph now shows the estimated strength of the signal in units of decibels above one microvolt or dBi It is partially computed as the ray is being traced through the ionosphere The final value is determined when the ray actual ly reaches the ground For this reason the signal strength bar graph may jump around a bit as each ray is being traced from one point to another This is normal It is important to remember that the signal strength computed with this simple r ay tracing technique is subject to inaccuracies that cannot be accounted for with this simp ler ray tr
158. it the ground this step is skipped All other maps begin the contouring You can interrupt the cont ouring at any time by pressing the ESCape key once The map is considered complete after the map is titled at the bottom edge of the screen When this occurs you have several additional commands at your disposal You can generate GIF or PostScript images of the screen by pressing the G or P keys respectively You can send the screen to your dot matrix printer by pressing the H key Or you can return to the PROPLAB Main Menu by pressing any other key such as the ESCape key 118 SECTION 10 ANTENNAS PROPLAB PRO Version 2 0 comes equipped with numerous types of antennas that can be immediately selected and put to work Main Menu Option 10 places you in the antenna selection menu PROPLAB will also process custom made antenna files that contain custom built an tenna radiation patterns PROPLAB will not compute the radiation pattern based on the orientation of your antennas radiation elements To do this you must use other types of softwa re 10 1 Selecting Existing Antennas From the antenna menu scroll through the list by pressing ENTER until you find an antenna that most closely approximates your own Then enter the number beside th at antenna to select it The information presented beside each selectable antenna in the antenna menu gives important information about each antenna The maximum gain figure describes the maximum gain o
159. itical frequencies As the evening spreads into night the F2 layer slowly erodes and becomes less capable of reflecting higher frequencies in other words the critical F2 layer frequency or foF2 decreases The critical F2 layer frequency usually reaches a minimum in the hours just before s unrise Those familiar with ionospheric radio signal propagation may realize that radio signals are split into two component waves an ordinary wave and an extraordinary wave Signals are split into these component parts by the Earth s magnetic field PROPLAB igno res this splitting effect and shows you only the ray paths of the ordinary waves Inclusion of calculations for the extraordinary wave would require a significantly higher num ber of complex calculations that would make even many state of the art computers choke For this reason only the ordinary waves are modeled in PROPLAB This does not limit or diminish the capabilities or accuracy of PROPLAB to any significant degree 2 6 3 The International Reference Ionosphere The International Reference Ionosphere or IRI is a collection of electron dens ity height profiles that are used within computer code to generate realistic profile s of the ionosphere The IRI references one of two different models developed by two orga nizations URSI and the CCIR Both of these models can be used within the IRI code through the use of numerical coefficients to describe the world wide behaviour of ionospheric pr operti
160. itter the probability of the ray encou ntering data gaps increases This is because as the distance increases the amount each successive profile overlaps the preceding one decreases The above discussion illustrates how PROPLAB is able to compute ionospheric parameters for rays that deviate away from the great circle path However we st ill do not know how PROPLAB computes the ionospheric profiles along each of these different bearings We 61 have until now assumed that PROPLAB simply knows the ionospheric characteristics at every possible point in distance between the transmitter and receiver on specific bear ings adjacent to the great circle bearing This is essentially true because PROPLAB performs inte rpolation to make it true But in reality the interpolation performed introduces possible ar eas where traced rays may begin to deviate from reality The following discussion explains why When setting up the parameters in suboption 21 of the Comprehensive Options me nu PROPLAB prompts for the distance in kilometers along each bearing to compute the ionospheric profiles This is followed by a prompt asking how many individual ionospheric s amples should be taken along the specified distance up to a limit of 46 For example if on each desired bearing within the bearing range you want PROPLAB to generate ionospheric profiles along a 15 000 kilometer path you can instruct PROPLAB to generate up to 46 ionospheric profiles along that p
161. itude above the surface 102090 40 50 eb 70 80 90 100 110 120 190 140 150 of the Earth is indicated by the Figure 3 0 Collision Frequency Profiles using 2 bottom scale from 0 to 150 km exponential terms for frequencies from 10 to 0 1 MHz Collision frequency is indicated by the vertical scale As can be seen as the frequency of the ray is increased the effect of the collision frequency decreases so that higher frequencies do not play as large a role in collisions as low frequencies For those who are familiar with the exponential models of collision frequency the exponential terms and reference heights which define the shape of these profiles can be adjusted if necessary using other options in this Comprehensive Options menu 3 3 18 4 Electron Density Model This is the option that lets you choose which type of electron density model to use in PROPLAB s comprehensive ray tracings The default is one of the three dimensiona 1 models These models are discussed in detail in Section 3 3 4 2 Consult that section for more information regarding the type of models to select 44 3 3 18 5 Integration Method PROPLAB PRO s comprehensive ray tracing technique contains numerous complex equations that must be integrated in order to ray trace signals These methods are a little bit older but produce reliable results The first choice selects the Runge Kutta int egration method while the second choice selects the Adams Moulton me
162. ity of the skip zone This is known as MUF or skip fading and can result in very dee p fade outs followed by very strong fade ins Highest signal qualities for this scenario wou ld occur over central America and southern Mexico within the first hop signal distance and o utside of the skip zone The signal deteriorates from there due to multi hop propagation and associ ated absorption etc Although not shown here a similar broadcast map showing the density of rays con verging within certain regions would be useful for determining areas where ionospheric focusing or defocusing may be occurring Together with the signal quality map it is possible to determine 95 where signal qualities correspond with ionospheric focusing to produce exceptionally good propagation conditions Although ionospheric focusing may in theory increase s ignal strength you must keep in mind that signals may differ in total distance travelled to pro duce multi path types of distortion and decreased signal quality For example a two hop signal may focus with a one hop signal to perhaps increase signal strength or produce destructive inte rference or even beating between the two signals In either of the two latter cases signal disto rtion and fading would be observed that might decrease signal quality even if the signal strength is increased For maps depicting the density of rays focusing or defocusing the values with in the key indicate how many rays strike the groun
163. latitude and longitude of the transmitter and receiver If this has already been set simply press ENTER to use those values PROPLAB next asks you to type in the distance in kilometers for the MUF If you press ENTER at this prompt PROPLAB will automatically calculate the MUF for the distance between the transmitter and receiver If you specify a distance the MUF will be computed at that distance on a bearing azim uth towards the destination PROPLAB will always compute the MUF for the shortest path betwe en the two points PROPLAB rigorously calculates the MUF That is it searches for a skip distance that coincides with the desired MUF distance and selects the maximum frequency at that distance This is a much more complicated procedure than most algorithms used in simpler p ropagation programs Those programs basically compute the MUF using empirical algorithms th at may assume simplified ionospheric parameters For example some routines used by other programs are able to rapidly compute the MUF by referencing very simple models of ionosph eric layers Others attempt to take into consideration effects of geomagnetic activity In many cases the results of these programs are fairly accurate but may completely fail during ge omagnetic storms or other phenomena PROPLAB makes only very few simplifications to help speed up the process of find ing MUFs It will only consider two control points on the path between the transmitt er and receiver The
164. lision Frequency and Profile Shaping Parameters 2 amp 228628 8h eee Oe ae oe eee 3 3 18 20 Three Dimensional Data Important 3 4 PROPLAB s Main Menu Functions 000 3 4 1 Ray Tracing Signals o605 ee eh ee ha ew be ee eben ec kas 3 4 1 1 Ray Tracing Signals using the Simple Ray Tracing Technique uke ght Oe te Sook tee A Boe NA 3 4 1 2 Ray Tracing Signals using the Comprehensive Ray Tracing Technique 2 4 6 66h eh ee eee he ena ee eS 3 4 1 3 Understanding the Generation of Ionospheric Profiles 3 4 1 4 Understanding the Three Dimensional Grid 3 4 1 5 The Text File Ray Tracing Results 3 4 2 Computing MUFs between any two points 3 4 3 Setting up Regions of Sporadic E 3 4 4 Setting up Transmitter and Receiver Locations 49 50 50 51 53 53 53 3 4 5 Plotting Electron Density Profiles 70 3 4 6 Displaying Ionospheric Profile Statistics 71 3 4 7 Quitting PROPLAB and returning to DOS 73 SECTION 4 GLOBAL IONOSPHERIC MAPS _ 2 2 0 0 0000005 73 4 1 Global Maps of Critical F2 Layer Frequencies 75 4 2 Global Maps of Ionospheric M Factors 0 00 77 4 3 Global Maps of Maximum Usable Frequencies 77 4 4 Global Maps of the Height Maximum of the F2 Layer 79 4 5 Generating Maps
165. lue of 5 a maximum value o f 30 and a stepping rate of 5 MHz By pressing ENTER at each of these prompts the software automatically contours from the minimum computed value to the maximum computed v alue at step increments that would result in maximum contour resolution In other words by default PROPLAB will produce maps with the greatest number of possible contours PROPLAB will allow up to 25 individual contour lines per generated map PROPLAB also gives you the ability to define what color to use when drawing cont ours You can select one of 15 different colors The default color is light cyan 75 If you have previously saved a map with information on it such as the sunrise su nset grayline location of the auroral zones signal path etc you can inform PROPLA B to use a previously saved map and superimpose all contours on that map This powerful fea ture lets you integrate maps of different types and superimpose contours on those maps For ex ample by pressing the S for Save key while editing sporadic E regions or graphically setting new transmitter and receiver points you can save the screen image to disk and later use that same map projection to superimpose contours of ionospheric quantities While PROPLAB is drawing contours a small box will flash red and white at the t op right hand corner of the screen This is used to tell you that PROPLAB is busy thinking You can abort the drawing process anytime by pressing the ESCape ke
166. me spread of signals in milliseconds anywhere within the bro adcast coverage range specified Voice communications can usually deal with fairly strong propag ation multipathing before deteriorating to non intelligibility However multipathing will degrade signal quality by increasing distortion and fading Multipath ranging maps may therefor e be useful to help determine possible areas of distortion and fading After you have ray traced the signals to produce the output dataset in the file PATHS OUT you can construct any of the four available maps without having to retrace rays The last map produced by PROPLAB is a simple map showing you the average time in milliseconds required for signals to travel from the transmitter to any point w ithin the broadcast coverage range area This is known as a propagation delay map 6 5 Required Map Generation Inputs 96 PROPLAB first asks you whether you want to use a previously generated map or a f resh map from the map library If you have previously generated a broadcast coverage map and wish to supplement it with additional information gathered by another ray tracing run select S to use the previously generated broadcast coverage map Alternatively if you have previously generated a map of maximum usable frequencies etc or a map showing the location of the auroral ovals sunrise sunset grayline sporadic E etc you may use that map in stead of a fresh map from the map library by selecting to
167. methods you can use to trace signals through the ionos phere The first is by holding the frequency of the signal and the time of the transmis sion constant and 54 sweeping the elevation angle of the transmission The second is by holding the elevation angle and time of transmission constant and sweeping the frequency of the signal And the third is by holding the elevation angle and the frequency of the signal constant and sweepin g the time of the transmission By sweep we mean to increase the value from a lower value to a higher value in user specified steps or increments Each of these three methods provide valuable and different results For example most radio transmitter antennas are capable of transmitting in specific or preferred directions That is their radiation patterns are usually higher in certain directions These are called directional antennas Omni directional antennas are associated with radiation patterns that are essentially equal in all directions That is the power transmitted away from the antenna is equal in all directions By selecting ray tracing by sweeping elevation angles you can essen tially analyze the performance of specific transmitters by sweeping transmission elevation angl es in accordance with the radiation pattern of the antenna To clarify let s assume that you have an antenna that is most efficient in transmitting between 4 and 12 degrees of elevation above the horizontal That is most of the power is r
168. milar results but obtains them in a different manner The first two Appleton Hartree models include effects of the Earth s magnetic field which therefore allows both ordinary and extraordinary rays to be traced However th ey differ in that the second model does not include the effects of electron collisions with neutral particles a significant phenomenon that is directly responsible for a producing most of the observed ionospheric absorption The second and third models are similar to the first two except neither of these two 42 models include effects of the Earth s magnetic field Only ordinary rays can the refore be traced using these two models They differ in that the third model does include effects of electron collisions with neutral particles whereas the fourth model does not The fifth model computes the refractive indices and associated gradients using a different method than the Appleton Hartree models but produces similar results It will likely only be of interest to those with a knowledge of the differences between the Appleton Hartr ee and Sen Wyller methods This model does not include effects of the Earth s magnetic field but it does include the effects of electron collisions with neutral particles The default and recommended model is the Appleton Hartree formula that includes effects of both the Earth s magnetic field and electron collisions with neutral particles Model 1 This model will produce the most accurate ra
169. n is not impinging on the ionosphere when the Sun is not in the sky For these reasons you can utilize the maps of solar zenith angles to determine where the strongest SWFs may be observed 4 7 Producing Maps of Magnetic DIP Angles PROPLAB will produce maps of magnetic DIP or angles of inclination Since many parameters in radio propagation are dependent on the magnetic DIP or inclination angle these 81 maps may be useful in the study of radio propagation They are included here for convenience Magnetic DIP angles do not change substantially over time and are not dependent on sunspot number or geomagnetic activity even though you may be required to input these va lues they are common inputs for all maps 4 8 Global Maps of Magnetic Field Total Intensity PROPLAB uses models of the Earth s magnetic field One of the modelled parameter s required for determining ionospheric characteristics and propagation conditions is the total intensity of the magnetic field You can map this parameter using this option As with the magnetic DIP angles this parameter does not change significantly according to s unspot number time or geophysical activity and is included here for reference purposes Label led contours are in units of gammas or nanoteslas 4 9 Global Maps of Magnetic Latitude It is often useful to know what magnetic latitude certain features of the Earth are located at Since radio propagation is closely linked with magnetic lati
170. n may observe sma ll field variations on the order of several gammas defining a quiet interval On the ot her hand it may be normal for a high latitude station to observe field variations on the ord er of several tens of gammas defining a quiet interval for that region For this reason each station is assigned their own rating scale However all stations scale their measurements so that their K index values fall within the 0 to 9 range The range used 0 to 9 defines the level of activity observed from dead quiet 0 to extremely disturbed 9 The amplitude range of the magnetic field during a give n 3 hour interval that is the maximum value minus the minimum observed value in gammas is used to determine the K index value The K index is quasi logarithmic and open ended Each observatory uses a look up table created for that specific location to convert an amplitude range into an associated K index value The table given below shows the look up table for a typical middle latitude magnetic observatory The a indices for a particular station may be converted into units of gammas by multiplying them by a station specific factor This factor can be found by divid ing the stations minimum value for a K index of 9 in this case 400 by 250 So for this case a K index of 5 would be associated with an a index of 27 which would convert to a magnetic field variation of 27 x 1 6 400 250 1 6 77 gammas Another term commonly used
171. n menu gives you the ability to define regions of spo radic E For this function to operate properly you will need a Plate Carree map projection available in your map library If one is not available PROPLAB will notify you and return yo u to the main menu To create a Plate Carree map use the utility MAKEMAP EXE To define regions of sporadic E you will need a mouse hooked up to your compute r When first selecting this option you will be asked whether you want to define the locations of the transmitter and receiver by pressing X or regions of sporad ic E by pressing S Press S and hit ENTER to define regions of sporadic E 68 If you have a Plate Carree map in your map library the software will ask you if you want to use the map present in the map library If you have more than one Plate Carree map projection in your map library you can select the map you would like to use by skipping the unwanted maps After you have selected the desired map PROPLAB begins computing the position o f the auroral ovals and displays the ovals superimposed on the desired map along with the position of the grayline Sun and the current signal path defined by the transmitter and receiver locations In addition regions of sporadic E which you may have used in previous runs are displayed on screen Altogether a great deal of information is made available on screen You can determine for instance the proximity of the signal path to the auroral z
172. n the Sun falls below the horizon at sunset this value will become negative When the sun rises above the horizon at sunrise this value will become positive 5 11 Height or Altitude of the Ray As a ray travels through the ionosphere the height of the ray is continually up dated beside the acronym Height located on the fifth line of the top right panel of the ray tracing screen The given height is in kilometers 5 12 Plasma Frequency at the Ray Height The plasma frequency at the ray height is listed beside the Plasma variable in the top right panel of the ray tracing screen the seventh line down The plasma freque ncy is given in units of MHz 5 13 Signal Elevation Angle The angle of elevation used at the transmitter to broadcast the signal is given beside the variable Sig Elev It is given in units of degrees above the horizon A zero degree elevation angle therefore corresponds to a transmission directed at the flat horizon An angle of 90 degrees denotes a vertically propagated signal 5 14 Auroral Zone Statistics The three lines in the top right panel of the ray tracing screen labelled Aur L AT Aur LON and Aur Dist describe the geographical position of that part of the equa torward edge of the auroral zone closest to the travelling signal The Aur Dist variable te Ils you how far in 89 kilometers the signal has spent inside of the auroral zone Signals that have not or do not pass through the aur
173. nd analy zed by PROPLAB functions which will for example plot the locations of traced rays on global maps produce contoured field strength maps etc Since you cannot stop PROPLAB from w riting this information you must only decide whether you want to A ppend the results to the file or C reate an entirely new file effectively truncating any existing data and rewr iting the file from scratch If you choose to C reate the ray database file PROPLAB will erase an y contents that may already exist in that file So be careful If you recently performed a large ray tracing session and do not want to lose that information but you do want to trace a different set of rays along a different path then go to the DOS prompt and rename the database file RAYOUT DAT to something else before responding to this prompt To abort this prompt without doing anything press the ESCape key For most applications you will pr obably C reate a new database file each time you trace rays through the ionosphere In cases where you may be performing several ray tracing sessions that are all related that is they have the same or similar paths transmitter receiver locations frequencies etc you may want to A ppend the results to the existing database file so that the database of information is sup plemented with the new results After inputting the starting ending and stepping values you are asked whether or not you want to Use the existing electron density prof
174. nd thereby perhaps introduce additional 34 62 maa 21 15 is interference as distance is increased As 27 69 a al ss 24 23 HL fStop z well in order to eliminate multipathing i op toa B area ral A 55 interference transmitting antennas must z m aan n perg M Ei IE ME become more directional with sharper pene a op nm appel fe 7 s F ae md IE 8 radiation patterns Otherwise signals will xc 0 09 o BHELL Se PAT a ee a A begin to travel using more than one mode of Figure 8 4 Elevation Angle Ionogram from Hawaii to propagation and the receiver will as a result Colorado 5 300 km Compare with Figure 8 1 experience an increase in multipathing signal degradation Figure 8 4 shows that the MUF for the HF spectrum is associated with a 2 hop sig nal that is transmitted between elevation angles of approximately 6 0 and 8 0 degrees If the transmitting antenna is incapable of concentrating energy below 8 degrees in elevation then the 3 hop mode of propagation must be used Notice that the 3 hop mode of propagation has a sma ller MUF than the 2 hop mode Frequencies above the 3 hop mode MUF would therefore not be rece ived at all if the transmitting antenna failed to radiate power below 8 degrees You would therefore be restricted to communicating on frequencies less than 14 MHz These are important concepts which can be used to significantly improve communications between specific point s
175. near eastern Australia where the sun is rising and the F2 layer is being rapidly ionized Gradients can be determined by examining how clo se the foF2 contours come to each other In general the stronger the gradient the less sta ble the ionosphere is and the more likely signals will experience non great circle propagation thro ugh resulting horizontal tilts in the electron density gradient PROPLAB will not take horizon tal tilts into consideration for computing possible non great circle paths Future versions of PROPLAB may however Radio signals which are propagating through the ionosphere are most stable where the contour gradients are weakest or farthest apart OR when signals use paths that FOLLOW the gradient contours The latter may require further explanation Signals that pass through high gradient regions are more susceptible to non great circle propagation and may ex perience less stable conditions However these effects can be minimized if paths are chosen t hat follow as closely as possible the contour lines in high gradient zones For example on t ransmissions from eastern Australia to Mexico the signal path crosses the foF2 contours at almost perpendicular angles In other words the signal path goes AGAINST the gradient of the contours and is more likely to experience non great circle propagation and instabilities Under these conditions PROPLAB may be less accurate than usual particularly on sunrise crossing circuits On the
176. ng you the effects of ionospheric tilts and non great circle propagation on specific azimuths The remainder of this section makes the assumption that you have already completed a ray tracing session and are now within the utility to process the results into viewable broadcast coverage maps 9 1 Types of Broadcast Coverage Maps Supported The first menu presented by the comprehensive broadcast coverage mapping system software lets you select the type of quantity you want to map The first choice which is the default lets you create a broadcast coverage map of the signal strengths of the rays that reached the ground during the comprehensive ray tracing session The second type of map that is supported is a map of propagation delays in mill iseconds This choice creates a map that shows you how long it takes signals to travel fro m the transmitter to the locations where the rays hit the ground This may be used for example to help in determining multipathing that can affect digital communications The third type of map supported displays the maximum or minimum angles of arrival elevation angles at the reception point where the ray reaches the ground This is useful for determining the range of angles with respect to the horizon that signals are received It can be used to help in the selection of appropriate reception antennas for example an tennas that have maximum gain within the range of indicated angles of arrival The fourth type
177. nhance signals in the VHF bands Polar Cap Absorption may devastate interfering transpolar signals and thereby enhance wanted signals from other less affected paths Similarly blanketing sporadic E can be responsi ble for blacking out communications on a wide swath of the available HF bands while pro viding improved propagation and greater range for others PROPLAB gives you the ability to determine how to make the best use of your resources during ionospheric disturba nces of a wide variety However we must first understand some of the more basic fundament als of radio propagation through the ionosphere 2 6 1 Ionospheric Reflection and Refraction 14 Reflection and refraction are important concepts which must be understood before ionospheric radio propagation can be understood to any degree of usefulness To help explore these concepts it is useful to adopt the idea of a ray or single beam of ligh t and what happens to a ray of light as it strikes or passes through various types of mat erial If a ray of light strikes a highly polished surface such as a polished chrome s urface the rays of light that fall upon the surface are reflected No light passes into or through the chrome material due to the opaque nature of the polished metal More accurately if a ray strikes a polished surface at an angle of 5 degrees the reflected ray will also make an angle of 5 degrees away from the surface of the polished material Likewise if a ray of lig
178. nomaly and near sunset Over time you will gain experience in using and applying these maps and will be gin to learn how the ionosphere responds to the seasons and even events such as geomag netic storms For example MUFs may increase over the equatorial regions during geomagnetic st orms while decreasing substantially as the latitude is increased 79 4 4 Global Maps of the Height Maximum of the F2 Layer The maximum height of the F2 layer is a critical parameter that can strongly inf luence the distance related to a given maximum usable frequency For example if the MU F over the U S is fixed at 25 MHz for a distance of 3 000 kilometers increasing the height of maximum electron density in the F2 layer would increase the distance for which this MUF applied It may also increase the actual MUF Decreasing the height maximum of the F2 layer als o known as the hmF2 would decrease the distance for which the MUF applied and may also de crease the actual MUF Gradients in hmF2 can also change the path of a signal from one which follows the great circle to one which deviates therefrom Using paths that are both stable in crit ical frequency and stable in hmF2 usually give reliable and often strong signals These are the pat hs which should be sought if communication reliability desired If reliability is not as significant as MUF then greater emphasis should be given to maps of maximum usable frequencies The height maximum of the F2 layer
179. nsmissions frequencies should be kept below the E layer MUF If frequencies exceed the E layer MUF the signals will penetrate the layer and travel to the F layer for reflection which results in long distance communicati ons This is desirable if you are only interested in long distance communications where F lay er signal propagation is a must In this case the chosen frequency must reside between th e E layer MUF and the F layer MUF If the frequency you choose is above the F layer MUF the s ignals will penetrate the ionosphere and be lost to space ORNYAUDNDY ORNYAUDNDY oooooo0oo0oo000 z u A f 5 5 a7 Lg uc a c3 oc mo e nu bs pad ao can ged ne reg lu 3 Noo uc od 505 Zau aug g5 QE L itn giv STE it WO e 2 i i F a a T N 012345 67 8 910111213141516 1718192021222324 Universal Time of 95 09 28 The optimum working frequency the FOT line in the above graph is a line which tends to result in the most reliable communications statistically speaking However there are often a range of frequencies near the FOT that can be used reliably This range of fre quencies is indicated by the thin line in the Figure above This line is the average of the F layer MUF and the E layer MUF The range of most useful frequencies is indicated by the spacin g between the FOT line and this thin line In the above example the FOT line tends to represen t the upper limit for useful frequencies while the thin l
180. o allows you to enable or disable the automatic computation of th e sunspot number if you also are using the BCAST Solar and Geophysical Database Management Software If you are not using this software this feature should be disabled to permit manual entry of the sunspot number If you have the BCAST software installed and enter a date which is in the BCAST database PROPLAB will automatically attempt to compute the 12 month mean sunspot number from the BCAST database for median results the 12 month mean sunspot nu mber is recommended It will also extract the geomagnetic A index for the given date from the BCAST records and automatically modify these parameters for the new date chosen If you want to maintain full control over what values are input disable this au to computation feature and enter in the data manually If this feature is enabled you will notice a time lag while the system tries to retrieve the necessary data from the BCAST database If PROPLAB cannot locate the BCAST database it will abort without any changes The DOS environment variable BCAST should point to the directory containing the databa se 3 3 7 Setting the Transmitter Power 36 This option applies to both of the ray tracing techniques NOTICE Previous versions of PROPLAB required the input of a relative transmitter power figure PROPLAB PRO Version 2 0 no longer asks for this It instead requi res the actual power of the transmitter in Watts For example a 1
181. oached This effect is called ionospheric focusing and can result in significantly higher signal strengths than is normally possible Figure 2 6 shows a magnified view of the downgoing rays and a typical if not somewhat exaggerated example of ionospheric focusing Each ray has been tagged with a number indicating the elevation angle used at the transmitter It can be seen that as the elevation angle increases from 10 degrees to 18 degrees the distance of hit the ground at progressively smaller distances Eventually a point is reached where the rays reverse direction and begin each ray from the transmitter Wie fa dec E decreases As well the i Di proximity of each ray to each Figure 2 6 Illustration of Ionospheric Focusing other ray decreases thereby increasing the concentration of 23 signals per unit area As the elevation angle of the rays is increased further a point is reached where further increases in elevation cause the rays to increase in distance away from the transmitter resulting in signal defocusing These rays are called high angle rays High angle rays are inherently unstable since very small changes in elevation angle can result in very large changes in propagated distances For this reason high angle modes of propagation are usually unsuccessful or at the very least unstable Signals associated with high angle modes are also usually fairly weak due to the defocusing which occurs However under some spec
182. of map shows you the geographical locations where the rays reach the ground from the transmitter It will display either ordinary or extraordinary rays or both together This type of map is extremely useful for observing how far signals de viate from great 115 circle paths It can also be used to display the skip distance from the transmit ter more precisely than the contoured signal quality maps provide and should be used to more precis ely determine locations where skip distance focusing may be occurring The last choice of the menu does not produce a graphical map but rather display s the contents of the ray tracing database file RAYOUT DAT on screen in a textual form at This can be very useful when you need to determine for example the precise signal stren gth or other characteristics of the ray that most closely approaches the receiver location o r the characteristics of signals that have a negative signal strength non existent in other words 9 2 Type of Rays to Include PROPLAB s broadcast coverage mapping system will analyze ordinary or extraordina ry rays or both types of rays to produce coverage maps At this prompt select the type of rays you want included in the analysis The default is to include both types of rays as both ordinary and extraordinary rays are receivable by all antennas 9 3 Specifying the Window Corner Coordinates of the Map When PROPLAB produces a broadcast coverage map using the results of a compreh
183. of the signal as it is being traced through the ionosphere using the azimuth given in Section 5 1 Using this feature you can determine the geographical coordinates where your signal p enetrates into the ionosphere or where it crosses into the auroral zone or where the signal 1 oses much of its quality or the locations of ground hops etc 5 4 Signal Air Distance Statistic The distance a signal travels from a transmitter to a receiver is not the same as the straight line ground distance from the transmitter to the receiver The signal m ust travel further than the ground measured great circle distance because not only is the signal travelling horizontally toward the receiver but it is also travelling upwards and downward s into and out of the ionosphere The AIR DIST or air distance statistic shows you how far yo ur signal has 85 actually travelled not the ground measured great circle distance usually report ed by propagation software 5 5 CURrent Angle of the Signal As a signal travels from the transmitter to the receiver the angle of propagati on of the signal will change from one instant to another For example a signal that is sh ot at a zero degree elevation angle directly at the flat horizon will increase in height by about 1 kilometer every 112 kilometers of distance it travels because of the spherical shape of the Earth To prove this hold a ruler flat against a sphere and see if the distance from the ruler to the center of
184. ofiles over a range of bearings that are centered on the main great circle bearing to the receiver For example if the bearing from the transmitter to the receiver is 100 degrees you can use this op tion to develop ionospheric profiles that might span for example a 5 degree bearing spread on either side of the great circle bearing PROPLAB would then create ionospheric profiles spanning fr om 95 to 105 degrees Another prompt presented within this option determines how many profile s to build along the bearing range In other words you are asked to type how many ionosphe ric profiles should be built between the 95 to 105 degree bearing range The more profiles yo u build along the bearing range the less likely PROPLAB is to trace a ray through a location where the ionospheric characteristics cannot be determined To help explain why PROPLAB might not be able to find an appropriate profile re fer to Figure 3 2 The two X s shown in this figure correspond to the transmitter and r eceiver locations The great circle path between these two points is represented by the imaginary straight line between the two X s In this figure we have generated eight ionospheric profile s that describe the characteristics of the ionosphere between the transmitter and receiver at ei ght different azimuths indicated by the eight shaded regions in Figure 3 2 When a sufficient number of profiles are generated along the bearing range the profiles begin to overlap so that th
185. olar zenith angles 79 80 Spectrum Analysis 98 Oblique Ionogram 99 Sporadic E 2 11 68 90 100 105 SSC 6 Sudden impulse 5 Sudden storm commencement 6 Sun 3 average radius 3 central meridian 6 chromosphere 4 corona 4 coronal mass ejections 5 differential rotation 4 distance 3 gravitational pull 3 interior 4 magnetic fields 4 mass 3 photosphere 4 rotation rate 3 Sunspots 4 temperature 4 volume 3 Sunrise 19 30 Sunset 19 30 Sunspot 37 Sunspot number 100 Sunspots 4 bipolar 5 direction of rotation 4 magnetic fields 4 temperature 4 Superimpose 98 Sweep 17 Sweep frequency 99 SWFs 80 Terminator 1 Terrestrial 3 Three dimensional ionosphere 58 Time zone 29 Transmitter height 45 Transmitter power 36 Transverse plasma frequency map 81 Twilight 30 Universal time 29 URSI URSI 19 Usable bandwidth 3 UTC 29 Viewing window 46 Warnings grid bounds 59 World Warning Agency 68 WWA 68 X rays soft 2 Zoom 49
186. om the ground That is it appears as though you are an observer looking at the traced rays perpendicularly In this mode yo u cannot discern lateral deviations easily if at all But you can determine the altitude the ra ys travel This mode can also be simulated using the three dimensional grid by appropriately rotating the display axes The third display method graphically displays rays traced through the ionosphere by assuming you are looking directly down upon the rays from above In this mode you cannot discern the altitude of the rays This mode is useful if you are interested in t he extent to which rays are being laterally deviated However the three dimensional grid will also let you look directly down upon the rays by rotating the grid appropriately The fourth display method is one of two available three dimensional graphical modes This mode displays the progress of the traced rays using the rotatable three dim ensional grid This lets you observe ray behavior from almost any conceivable viewing angle or perspective 45 The fifth display method is the second available three dimensional graphical mode It is similar to the last display mode described but differs in one important aspect In this mode ray paths are displayed while they are being integrated In the fourth display mode ray paths are only displayed at specific points along the ray path ex entering exiting the i onosphere progress toward ray reflection the location wh
187. on high frequency communication above 23 MHz may be possi ble but difficult Given that the transmitter radiates most of its power at about 15 deg rees in elevation it would probably be wiser to use a frequency between 17 5 MHz just above the 3 hop MUF and 22 5 MHz the 2 hop MUP and rely primarily on signals reflected twice by t he F region for communications Selecting these bounds for frequencies will result in minima 1 multipathing distortion There will be some multipathing caused by weak 1 hop reflections but most of the signal strength should come from 2 hop signals since the primary radiation angle is closer to that required for 2 hop propagation than for 1 hop propagation Frequencies below abo ut 17 5 MHz should probably be avoided since they may be associated with more significant m ultipathing of greater than 2 milliseconds examine the difference in propagation times between 2 hop and 1 hop propagation modes in Figure 8 5 caused by signals being received by both 1 hop 2 hop and 3 hop paths Since our transmitter will not radiate much power above 35 degrees in elevation 113 4 hop signals should not be observed which will limit signal multipathing to the 3 modes of propagation 1 hop 2 hops and 3 hops 8 5 Commands Available While Viewing Ionogram Plots There are several commands at your disposal while you view the ionogram plots pr oduced by PROPLAB These are summarized below Press G after the plot has been comple
188. ones where if at all the signal crosses into the auroral zones whether the signal spends any time and how much time in daylight or darkness and even whether the signal crosses regions of sporadic E With this information in hand you can begin defining regions of sporadic E with your mous e Moving the mouse moves the mouse cursor on the screen Regions of sporadic E are defined by marking rectangular regions with the mouse cursor This is done by po sitioning the mouse cursor to the upper left corner of the desired sporadic E region and click ing on the LEFT mouse button A corner pointer will be placed on the screen where the left butto n was clicked Now move your mouse over to the area where the bottom right corner of the sporad ic E region exists and click on the RIGHT mouse button This defines the rectangular sporadi c E region PROPLAB next asks you to type in the critical frequency of the sporadic E region The value you type here determines how intense the ionization is within the defined rectangular region The ionization in turn determines the extent of signal refraction and reflection which can occur in that region Sporadic E can vary over wide ranges from critical frequencies of only about 1 5 or 2 0 MHz to critical frequencies as high as 30 MHz under rare conditions In most cases sporadic E varies between approximately 2 MHz and 10 MHz with an average maximum nighttime critical frequency of about 2 to 5 MHz Due to the unpred
189. ons Figure 8 3 Elevation Angle Ionogram from Hawaii to 36N 126W 3 500 km Compare with Figure 8 2 Again these black and white figures are actually full color on your monitor and each of the plotted lines are color coded so you can easily determine what plotted lines are associated with specific numbers of grou nd hops The Key in the upper left hand corner of the screen defines how many hops each of the colors represent The angle of elevations can be read off of the vertical grid from top to bottom on the far left of the screen where the propagation delay times were formerly determin ed in the last section In order to make optimum use of the ionosphere it is necessary to orient your antenna so that most of the radiated power is transmitted at specific angles of elevation Failure to do so limits how much control you have over where and how far your signals travel In order for a signal to reach the ship at 36N 126W from Hawaii it will be necessary to use one or more of the transmission angles of elevation shown in Figure 8 3 Some people might have problems understanding how to read the plot in Figure 8 3 To help in this regard let s examine the single hop line in Figure 8 3 This long plotted line covers frequencies from about 7 MHz up to the MUF of 23 5 MHz It tells you that for si ngle hop paths very low radiation angles of elevation between 0 0 and 3 0 degrees are re quired for signals to reach the ship at 36N 126W In addition
190. oral zone are associated w ith the acronym NoZone As is inferred this simply means that the signal does not pas s or has not yet passed through the auroral zones As the signal approaches an auroral zone the NoZone string will change to point to the geographical locations of the equatorward edge of the auroral zone that is closest to the signal These variables are continually updated 5 15 Ionospheric Distance Travelled A radio signal typically does not suffer any significant degradation until after it penetrates into the ionosphere The distance travelled within the ionosphere in kilometers is listed on the last line of the top right panel of the ray tracing screen by the variable Iono Dist This distance does not include the distance required for the signal to travel from the ground to the base of the ionosphere It only includes the distance travelled by the signal WITHIN the ionosphere 5 16 Identifying the Receiver Location When ray tracing signals through the ionosphere the location of the receiver is identified by the dotted green line extending from the base of the distance grid to the top of the ionosphere It is similarly identified in the electron density graph the top central panel as a dotted green line If the distance grid overlies the location of the receiver effectively hiding the location of the dotted green line the location of the receiver can be found by referencing the green arrow directly below the distanc
191. osphere by sweeping elevation angles frequencies azimuths or any or all of these three together The prompts associated with the elevation and frequency sweep selections are sim ilar to those for the simple ray tracing method and need no further explanation here The option to permit tracing rays by sweeping azimuths is new to PROPLAB PRO Version 2 0 but is self explanatory Enter in the starting and ending azimuths clockwise from true north east is 90 degrees azimuth you want to transmit toward in degrees Also enter in the rate with which you want to step the azimuth from the starting to the ending azimuth in degrees PROPLAB PRO Version 2 0 prompts for several additional items that are not presen t in the simple technique and in fact have not ever been present in prior releases of PROPLAB These prompts are described below 56 After selecting which component to sweep elevation angles frequencies or azimu ths you are asked to input the azimuth of the transmitting antenna in degrees clockwis e from true north This is the azimuth of the main radiation lobe of the transmitting antenna For instance if your antenna has a radiation pattern that radiates most of the transmitted power dire ctly toward the east you would specify an azimuth of 90 degrees If your antenna is rotatable specify the current azimuth of the antenna s main radiation lobe This is an important parameter that must not be overlooked PROPLAB PRO uses this info
192. ossible to see reflections in the wa ter such as your face At the same time it is possible to see a dime that has been placed at the bottom of the bowl Rays of light are both reflected from the surface of the water permitting you to see your reflection and rays of light are refracted into the water and reflected back permitting you to see the dime The degree with which a ray of light is refracted depends on the speed of light within the material where refraction takes place compared to the speed of light within the material where the ray is originating It also depends on the wavelength of the light that is passing between the two materials The speed of light within a material depends on the density of the material through which the light is travelling Light always travels more slowly through a material than it does in a vacuum The ratio of the two speeds is equal to a quantity known as the index of refraction Thus the 15 speed of light v in a material having an index of refraction n is given by v c n or n c v When light passes from one material to another its frequency does not change for the following reason When light interacts with matter the electrons in the material absorb energy from the light and undergo vibration motion with the same frequency as the light This motion causes reradiation of the energy with the same frequency Hence since the speed of light in a material is equal to the wavelength of the light w m
193. ote that PROPLAB will accept almost any set of angles here However some exotic angles may cause PROPLAB to improperly draw grid borders labels or other things Even so no harm can be done it may just be more difficult to see so feel free to play with this section until you find values that are aesthetically pleasing 3 3 18 16 Zoom Factors and X Y Axis Offsets PROPLAB PRO has the ability to display three dimensional grids that are zoomed in or out The X and Y axis offsets permit zooming centered on any location of the thr ee dimensional grid Zoom factors must be specified in percentages where zero percent represents an unzoomed screen A zoom factor of 100 percent will zoom into the three dimensional grid centered on the center of your monitors screen by a factor of 2 times the normal Similarly a zoom factor of 50 percent will cause PROPLAB to zoom out by 50 percent thereby making the three dimensional grid half the size on the screen The X and Y axis offsets are relative to the middle of your monitors screen not the middle of the three dimensional grid They are also both stated in percentages o f screen widths and heights The X axis offset defines the center location of the X axis of your screen The default value is 0 00 percent which corresponds to the 320th horizontal pixel on VGA displays A value of 30 0 percent corresponds to a location 30 to the left of the 320th horizontal pixel while a value of 30 0 percent cor
194. other hand a signal path from eastern Australia to the southern tip of South America more closely follows the foF2 contours and GO WITH THE GRADIENTS For this signal path greater signal stability and less non great circle propagation would likely be observed It is interesting to note that in this last signal path the signal is essentially a grayline signal or one which follows closely along the sunrise sunset terminator Maps produced with geomagnetic A index levels less than or equal to 5 can be con verted to monthly median maps if the sunspot number or solar flux value used is the ave rage value for the last 12 months By offsetting the geomagnetic A index or sunspot number it is possible to 77 adjust the maps for conditions that may more closely represent observed conditio ns In general the geomagnetic A index for the current UTC day as well as the sunspot number or solar flux value averaged over the last week or two are sufficiently accurate inputs to mo del approximate observed conditions It must be remembered that daily maps of foF2 may differ markedly from those produced here since the ionosphere is still a highly unpredictable region of our atmosphere 4 2 Global Maps of Ionospheric M Factors M factors were discussed previously and represent the ratio between the maximum usable frequency for specific distances and the critical F2 layer frequency For example an M factor for a distance of 3 000 kilometers would be computed by
195. per interpretation of these features shortly PROPLAB produces oblique sounding ionograms between two points by sweeping the H F spectrum at the transmitter and measuring the signals that reach the desired rec eiver The process is rather complex and can be time consuming for detailed results but the inform ation which can be gathered from such an analysis is well worth the time 8 2 Phase 1 Collecting the Required Data There are two phases to producing Oblique Ionograms with PROPLAB The first phas e is to collect the data The second step is the analysis phase which is discusse d in Section 8 3 This first data collection phase requires the most time but is extremely simple to set up 100 First you must make certain that the transmitter and receiver locations and par ameters are properly established using option 8 of the Main Menu Be sure that the relativ e transmitter power is set properly as well as the geomagnetic A index and the sunspot number or solar flux Also be certain that the date and time local or UTC is also properly entered These are the most critical parameters If sporadic E may affect the signal path make sure you use option 3 of the Main Menu to set up the regions of sporadic E If solar flares or PCA might inhibit commun ications enter the appropriate data in option 8 of the Main Menu Make sure that all of the items in option 8 of the Main Menu are properly establ ished for the signal path you wish to analyz
196. pheric profiles from 163 kilometers for 2 seg ments to 36 kilometers 15 000 km 9 segments 46 profiles per segment This is the best PROPLAB can do and is far better than we probably really need because in most cases ionosph eric characteristics do not change appreciably over distances as small as 36 kilometers Hence interpolation will not introduce any appreciable inaccuracies in the traced rays PROPLAB saves each segment of ionospheric profiles to a separate disk file within the PROFDATA subdirectory that is created when you install PROPLAB If you instruct PROPLAB to build 9 segments it will save 9 separate files containing all of the ionosph eric profiles for those segments PROPLAB saves one file for every step in the bearing or azimuth that is used as well For instance in our example where we built ionospheric profiles spanning a 10 d egree range at steps of 1 degree each PROPLAB would save 10 separate files to the PROFDATA sub directory one for the 95 degree bearing another for the 96 degree bearing and so on unti 1 the 105th degree bearing was saved By using a stepping rate of 0 1 degrees per bearing the num ber of saved files increases to 100 10 degree range 0 1 degrees per bearing The amount of disk space consumed increases dramatically if you are not careful in your selection of parameters The more profiles you build along each segment up to a maximum of 46 profiles per segment the greater the disk space will b
197. pping rate and traces a second ray through the ionosphere using the starting azimuth and the new angle of elevation This process is repeated until the last ray is traced re presenting the ending angle of elevation for the starting azimuth When this ray has been compl etely traced PROPLAB resets the angle of elevation back to the starting angle of elevation and increments the azimuth by the azimuthal step rate previously defined PROPLAB then retraces all of the rays from the starting angle of elevation to the ending angle of elevation at the new incremented azimuth and continues to reset the elevation angle and increment the azimuthal angle until the ending azimuthal angle is reached The process of computing the required data is then complete when the last ray of the ending azimuthal angle and the ending elevation angle is traced Following this PROPLAB automatically transfers control over to the broadcast co verage map generator subprogram known as ANALYZE EXE This entire process is time consuming but is accurate and can be made as accu rate as time permits using smaller angles of increments The resulting data file in PA THS OUT may be a respectably large file of many hundreds of thousands of bytes There is no limit on the size of the data file generated PROPLAB will handle files from several K bytes to ma ny megabytes PROPLAB is only limited by the size of your hard drive You can force PROPLAB to abort the computation of the data by
198. pressing the ESCap e key anytime during the ray tracing phase This will force PROPLAB to load the ANALYZE EXE module Premature abortion of this phase may result in inaccurate or incomplete or even perhaps non existent or non computable maps due to insuffic ient data 6 4 Types of Broadcast Coverage Maps Available There are four types of broadcast coverage maps that PROPLAB will produce after the appropriate data has been computed and collected see Section 6 3 PROPLAB will produce maps of signal quality showing you the quality of signals throughout the broadcast range specified PROPLAB will also produce maps showing you the density of rays per un it area This latter function is valuable for determining the effects of ionospheric focu sing or defocusing and therefore possible signal strength patterns PROPLAB will also compute the time delay of the signal from the time it leaves the transmitter to the time it reaches the gr ound throughout the broadcast coverage range and will produce maps showing the average time delay per unit area Finally PROPLAB will compute the multipath range of signals or ranges of time required for signals to reach specific regions It will produce maps of multipath time spread s which is exceptionally useful information for packet radio systems or other digital type communications Figure 6 1 is a sample broadcast coverage map showing signal quality from an omn i directional antenna located in Colorado broadcasting
199. r disk named MKMAPV1 EXE to create the older style map library You can now also customize the colors of the maps consult Section 3 2 of this manual for mee information FOR INDIVIDUALS UPGRADING TO VERSION 2 0 If you have an old version of PROPLAB on your computer yu MUST DELETE EVERYTHING in the old PROPLAB directory before installing Version 2 0 of PROPLAB PRO There are some significat changes to the way PROPLAB handles some of the files and utilities In order forit to be properly installed all old versions must be completely deleted from your hard dive unless you are installing PROPLAB PRO Version 2 0 in a different directory This doesNOT apply if you are installing PROPLAB PRO Version 2 0 in a directory that is comp tely separate from the old version However any DOS environment variables that referto the old version must be modified to point to the new version after it has been succesfully installed If you previously purchased our Professional Dynamic Auroral Oval Simulator you will notice that the older mono colored maps are used However the format of the map files are identical Those who use our Auroral Oval Simulator can therefore see whethe r they want to use the full color map databases by copying the MAPS LIB file from the PROP LAB directory into the directory containing the Auroral Simulation Software 26 After the installation procedure is complete you can execute PROPLAB from your MSDOS command prompt PROPLAB PR
200. r s impler propagation programs It uses a standard parabolic equation to describe the elec tron density 34 throughout the ionosphere Use of this model demands a fair bit of knowledge of ionospheric electron density shapes and a familiarity with the standard parabolic profile eq uations Before this model can be used to produce an ionosphere in which rays can be traced sev eral options must be defined in the comprehensive ray tracing options menu Main Menu 8 Sub option 18 In particular you must define the critical frequency of the F2 layer at the mid point of the path if this is unknown you can use the CCIR or URSI model with PROPLAB to print out the predicted critical F2 layer frequency use Main Menu Option 7 after defining th e location of the transmitter and receiver You must also specify the thickness of the F2 layer and the height where the electron density reaches a maximum in the ionosphere These parameters will be discussed in greater detail in the section which deals with these settable options This model is only valid for single hop paths Model 6 Alpha Chapman Two Dimensional Model This model is similar to Model 5 and requires the same type of information It is also only valid for single hop paths 3 3 4 3 The Right Model to Use There is no right or wrong ionospheric model The model you use will usually be dictated by exactly what you require However if you are not sure what you need or which model you
201. r sunris e or sunset Solar zenith angles greater than 90 degrees denote areas of the Earth that are in dark ness or twilight Astronomical twilight typically ends or begins when the sun reaches a solar ze nith angle of about 102 degrees or about 12 degrees below the horizon During solar flare activity maps of solar zenith angle are of primary importance for determining what areas of the world may be experiencing short wave fadeouts or SWFs A short wave fadeout is a period of time when shortwave HF signals suddenly or gradually fade out and disappear As flares increase in magnitude frequencies which can be aff ected by the activity increase For example a magnitude M1 0 flare may produce a SWF affecti ng frequencies up to 7 MHz Compare this with a magnitude X1 0 flare which may produce an inte nse SWF affecting frequencies as high as 15 or 20 MHz effectively wiping out communica tions on most HF bands The extent to which flares affect communications depends on the solar zenith ang le Low solar zenith angles or times when the Sun is high in the sky result in the strongest SWFs and affect frequencies higher than at any other location on the Earth As the solar zenith angle increases toward sunset or sunrise conditions the effects of flares decreases For solar zenith angles greater than 90 degrees when the Sun is below the horizon flares do not have any significant adverse effects on signal absorption since the ionizing radiatio
202. rate profiles eve ry 1 0 degrees in bearing 10 degree spread 10 profiles 1 0 degree PROPLAB will then gene rate the first profile at a bearing of 95 degrees the second profile at 96 degrees etc until the bearing exceeds 105 degrees You can increase the resolution of the profiles that is make them overlap more to reduce or eliminate gaps in data by increasing the number of profiles For example by specifying 30 profiles instead of only 10 you effectively instruct PROPLAB to produce ionospheric profiles every 0 3333 degrees in bearing 10 degrees 30 profiles 0 3333 degrees per profile PROPLAB would then create the first profile at 95 degrees the sec ond profile at 95 3333 degrees the third profile at 95 6666 degrees etc until the bearing in creased beyond 105 degrees Hence the lower the stepping rate the higher the resolution the grea ter the overlap in profiles and the less chance there will be for data gaps Gap in ionospheric profiles can cause inaccuracies in traced rays Figure 3 2 Gaps in Ionospheric Profiles see text The smallest stepping rate allowed by PROPLAB is a stepping rate of 0 1 degrees in bearing Even for very long distance paths near the 20 000 kilometer limit of PR OPLAB s comprehensive ray tracing engine this stepping rate usually suffices However be aware that as the distance between the transmitter and the receiver increases or rather as the ray moves farther and farther away from the transm
203. rcle path propagation This type of phenomenon is fairly common during d isturbed geomagnetic and auroral periods in the auroral zones PROPLAB is unable to consider each of these differing types of phenomena individually The main reason for this is the high level of unpredictability which exists for these types of activity Instead PROPLAB attempts to lump all of these differin g types of activity together to average their effects It would also be necessary to input several different types of data into the software for it to reliably take this activity into consideration Aside 12 from being unnecessary the required inputs would be difficult for the average r adio communicator to obtain Reasonable accuracy is obtained from the software withou t requiring these inputs 2 5 Polar Cap Absorption PCA Polar Cap Absorption is the result of intense ionization produced by energetic p rotons The protons originate from a class of large solar flares known as proton flares These types of flares successfully accelerate protons to a good fraction of the speed of lig ht When these protons reach Earth only minutes to hours later they spiral around and down the magnetic field lines of the Earth and penetrate into the atmosphere The high energy of t hese protons permits them to penetrate relatively deeply before being stopped about 40 to 80 kilometers high Some particularly powerful flares are capable of throwing out protons with energies in the GeV r
204. ree s per side In the second example the total bearing range would have been 2 degrees 1 degr ee per side This prompt is therefore essentially asking you what the stepping rate should be between successive sets of azimuthal ionospheric profiles The stepping rate can be comp uted by dividing the bearing range by the number of profiles you want to build along the bearing range For example if the bearing range is 20 degrees and you want to build 50 sets of pro files along that range PROPLAB would use a stepping rate of 20 50 0 4 degrees Assuming the main bearing is 315 degrees the first set of profiles would be built along the bearing 315 10 305 degrees The second set of profiles would be stepped by 0 4 degrees and would therefore be built along the bearing 305 4 degrees The third set of profiles would be built along the bearing 305 8 degrees etc in the end resulting in about 50 sets of ionospheric profiles cov ering the bearing range from 305 to 315 10 325 degrees in 0 4 degree increments This prompt is important for preventing data gaps in ionospheric profiles The next prompt posed by PROPLAB asks you to specify the distance in kilometers behind the receiver to begin computing the various sets of ionospheric profiles In most instances a value of 0 kilometers will be specified here indicating that the first profile generated along each bearing should be directly above the transmitter The following prompt asks you to spe
205. responds rapidly to changes in geomagnetic ac tivity Usually the hmF2 increases as geomagnetic activity increases over the middle an d high latitudes since heating in the lower portion of the F2 layer erodes the ionization of that portion of the ionosphere and causes the maximum height of the electron density to increase This may sound good from the point of view of increasing transmittable distances however incre ases in geomagnetic activity are also accompanied by an attended decrease in F2 layer el ectron density and hence critical frequencies for the same reason as given above This reduce s the MUF over all affected regions As it turns out the reduction in foF2 is usually more imp ortant than increases in hmF2 And since any increase in hmF2 is usually accompanied by a de crease in foF2 any positive effects of increasing hmF2 are nullified 4 5 Generating Maps of Critical E Layer Frequencies The critical frequency of the E layer or foE is heavily dependent on the locat ion of the Sun For high solar elevation angles or low solar zenith angles the critical frequency of the E layer reaches a maximum of between 3 to 4 MHz That is the frequency which wo uld cause a vertically propagated signal to penetrate the E layer would be between 3 and 4 MHz if the Sun were high in the sky As the Sun drops toward the horizon critical frequencies drop After the Sun sets ionization in the E layer abruptly ends and critical frequencies fall even fur
206. responds to a location 30 to the right of the middle of your screen The Y axis offset is defined similarly The default value of 0 00 percent corres ponds to the 240th vertical pixel on VGA displays A value of 30 0 percent corresponds to a location that is 30 above the middle of your screen while a value of 30 0 percent refers to a location that is 30 below the middle of your screen By adjusting these variables it is possible to zoom in to features of traced ra ys that might be difficult to see under normal circumstances 3 3 18 17 HMax and Altitude Grid Ym and foF2 Layer Shaping Factors This option will likely only be used by those who have a firm knowledge of the mathematical representations of ionospheric electron density profiles These options are used primarily by the Quasi Parabolic and Alpha Chapman electron density models and must be adjusted to the appropriate values prior to performing any raytracing The two dimensional electron density models CCIR and URSI require the foF2 critical frequency of the F2 layer parameter only The other two parameters HMax and Ym are not used in the URSI or CCIR two dimensional electron density models 50 The HMax parameter refers to the altitude above the surface of the Earth where the electron density reaches a maximum usually in the F2 layer This parameter is also used to adjust the height of the altitude grid wall on three dimensional displays For example to display a thr
207. ric pr ofiles This is accomplished by actually instructing PROPLAB to begin a comprehensive ra y tracing session use Main Menu Option 1 3 4 PROPLAB s Main Menu Functions The Main Menu of PROPLAB gives you access to all of the functions of PROPLAB and is responsible for loading and executing the appropriate subprograms when reques ted It consists of nine options which are described below 3 4 1 Ray Tracing Signals PROPLAB is very flexible in the way it permits signals to be traced through the ionosphere Before ray tracing can be accomplished it is important to setup the appropriate parameters in the Options Menu see Section 3 3 so that PROPLAB knows all about the signal you are transmitting from one point to another As has been noted in previous sections of this manual there are two main ray tr acing methods that are available a simple technique and a comprehensive or complex technique The first option of the Main Menu lets you choose which type of ray tracing technique you want to use Use the simple method if you are more concerned about a quick analysis of the way signals are reflected from the ionosphere Use the comprehensive method if you need accu rately ray traced signals that show you more precisely where signals are going Use a three dimensional model of the comprehensive method to see where signals go in three dimensions 3 4 1 1 Ray Tracing Signals using the Simple Ray Tracing Technique There are three different
208. rmation to compute the field streng th of the signal Entering the proper antenna azimuth as well as the proper type of antenna is necessary if PROPLAB is to produce reliable results The second prompt asks you if you want to Store text results in the file resul ts out When using the comprehensive ray tracing technique PROPLAB PRO will optionally create a text file and write various bits of information to that file while rays are bein g traced through the ionosphere For example whenever a ray reaches an apogee or perigee maximum he ight or minimum height respectively is reflected by the ground penetrates the ionosph ere or reaches the receiver PROPLAB writes information to this file Information written inclu des such parameters as the ground range the latitude longitude of the ray the polarization of the ray ionospheric absorption encountered geometrical path distance phase path group path and ray deviations and bearings etc This information can be used to gather more detail ed data regarding a particular traced ray If you want this type of information stored select y es at this prompt Be aware that the size of this file can become quite large fairly quickly particularly if the Runge Kutta integration technique is used if many rays are traced with this option enabled For each comprehensively traced ray PROPLAB writes specific information to a bi nary file in the PROPLAB directory This information can then be later read a
209. rmits the ray to penetrate either of the layers or the electron density increases and forces the signal to become imaginary It is this latter condition which forces PROPLAB to abort If it occu rs which should be fairly rare PROPLAB will impound the affect signal with a box Notice that the inability of PROPLAB to accurately trace rays through the ionosp here via inter layer reflections as described above is related to the simpler ray tracing technique employed The comprehensive ray tracing method will accurately compute such effects Hence rays are not impounded with boxes when using the comprehensive ray tracing techn iques 5 9 Magnetic Coordinates of the Ray 88 The first two lines of the top right panel of the ray tracing screen show you the magnetic latitude and longitude of the ray as it is being traced through the ionosphere This is a critical parameter Many of the functions and calculations used by PROPLAB depend on reli able magnetic coordinates For example polar cap absorption begins to strongly affec t radiowave propagation poleward of approximately 65 degrees magnetic latitude PROPLAB uses an accurate version of the Earth s magnetic field 5 10 Solar Elevation Angle at the Ray Location The third line of the top right panel tells you the solar elevation Sol Elv or the elevation angle of the Sun above the horizon at the current geographical coordi nates of the travelling ray This is a valuable number to watch Whe
210. s Again this model will produce inaccurate and unrealistic results unless the user is familiar with the appropri ate applications for this model We recommend using the second choice to select the Dipole Field Model For general applications this will produce the best and most reliable results 43 3 3 18 3 Collision Frequency Model This subsection defines the type of model that should be used to represent the e lectron collision frequency through the Earth s atmosphere It effectively defines the rate with which electrons collide with neutral particles in the Earth s atmosphere and ionosphere and is quite important for accurate computations of ionospheric absorption values The first choice defines a model that uses two exponential terms The second choice defines a model that uses only one exponential term while the third choice defi nes a model that has a constant collision frequency model The third choice will produce unrealistic results and should only be used by those who have a knowledge of the applications through wh ich such a model can be used By default the model with two exponential terms is used The difference between the first and second models supporting two and one exponential terms respectively is almost negligible Figure 3 0 shows the collision frequency profile for transmission frequencies that vary from 100 KHz to 10 MHz The lines are defined from left to right as follows 10 MHz 5 MHz 1 MHz 100 KHz Alt
211. s represent northern hemispheres Negative latitudes represent southern hemispheres Longitudes are given in a direction me asured west of Greenwich and never become negative Therefore values between 0 and 180 represe nt western longitudes and values between 180 and 360 represent eastern longitudes Bearing Defines the current azimuthal bearing of the ray as measured from the transmit ter In other words this value represents the bearing required for the ray to get from the transmitter to its current geographical location It is constantly being updated and gives you a good idea of the 65 extent to which non great circle deviations may be affecting the ray Absorption PROPLAB integrates the ionospheric absorption equations at the same time it integrates the ray tracing equations It is therefore a highly accurate measure of the total ionospheric absorption encountered from the time the ray left the transmitter to the current ray location and far exceeds the accuracy of empirical absorption calculations performed by most other propagation programs Phase Path This will likely only be used by those with a deeper knowledge of ionospheric radio propagation It indicates the phase path of the ray and is constantly upda ted as the ray is traced Sig Strength This value is the computed signal strength of the ray currently being traced It is only updated when the ray either penetrates the ionosphere or reaches or is ref lected by the ground I
212. se the F2 layer electron density and hence critical frequency decreases slower during sunset than it increases during sunrise In other words the critical frequency changes more abruptly and systematically during sunrise than it does during sunset Higher F2 layer critical frequencies will produce correspondingly higher MUFs for given distances since the increased F2 layer ionization will reflect signals with higher frequencies The map in Fig ure 4 2 shows MUFs in MHz for a path distance of 3 000 kilometers 78 When instructing tf PROPLAB to produce global maps f f of MUF you will be asked what distance to compute MUFs The default is 3 000 kilometers Most of the critical parameters for 3 000 kilometer MUFs have been precalculated Producing default 3 000 kilometer MUF maps are therefore significantly faster than producing maps of different path lengths Specifying paths of different lengths will force PROPLAB to rigorously compute 5 MUFs for those distances by quickly ray tracing through the ionosphere until the MUF for the given distance is found This can be a time consuming process particularly on slower computers or if high map res olution levels are chosen However the results can be very informative and helpful UNCON DOO e 6 S342 007 oO MAP OF MUFC3O00 gt _ 9 00 U uT 199 i INI Q
213. should select use one of the three dimensional models They tend to be a little more time consuming to set up but are not as prone to produce confusing results More importantly the results they produce are more accurate and easier to interpret Generally for most applications either the URSI or CCIR three dimensional mode Is will be of greatest value The two dimensional models should only be used if you are tracing signals through the ionosphere that you know will never need to be traced beyond one hop That is the signals should never be reflected by the ground and back into the ionosphere bef ore reaching or nearing the reception point Paths beyond 4 000 kilometers definitely should not use the two dimensional models Instead one of the three dimensional models should be used Models 5 and 6 are oriented more towards professionals who know the capabiliti es and uses for Quasi Parabolic and Alpha Chapman electron density equations If you are not familiar with these models selecting them may prove to be problematic and produce unreal istic results In other words if ever in doubt use either the URSI or CCIR three dimensional models They will automatically handle all of the things which the two dimensional model s do not such as recomputing electron density profiles at each point along the traced ray etc 3 3 5 Setting the Operating Frequency 35 The fifth option of PROPLABs Options Menu applies to both the simple and the compl
214. sing this software For this reason systems equipped with math coprocessors or 486 or better based computers are much better equipped to handle the large quantity of complex floating point calculations required for many of the functions of this package Use of coprocessors will sig nificantly speed up operations and are recommended for use with this software PROPLAB will operate fine if you don t have a math coprocessor in your system It will simply take more time to complete some of the functions We have made every effort to test this software for bugs Although we can t prom ise that all of the bugs have been corrected we hope they have If you find a bug in the software we would appreciate it if you would write to us and notify us of the p roblem Inform us of the type of computer system you have hardware configuration type and version of the disk operating system you are using as well as any other pertinent infor mation that will help us locate any potential problems in the system We will do our best to correct any problems that are found as quickly as possible Alternatively send bug reports to us on the Internet via Oler Solar Uleth CA or COler Solar Stanford Edu PROPLAB will print graphic screens directly to your dot matrix printer But befo re this can be accomplished PROPLAB s printer control file PROPLAB PTR must be modified to work with your particular printer All of the instructions necessary to alter this file are contained
215. smitter and the receiver It can therefore only trace rays out to a distance of 20 000 kilometers which is the circumference of half of the Earth and is the greatest short path distance betwe en two points The Termination Mode applies to both of the available ray tracing techniques and tells PROPLAB when you want it to stop tracing rays through the ionosphere If the sig nal strength or quality becomes degraded to the point where it is useless or blacke d out a white X is stamped on screen at the point where the signal vanishes the X is only displayed when using the simple method PROPLAB will normally continue tracing the ray through the ionosphere even though the signal quality or strength is at the blackout condition If you want PROPLAB to stop tracing rays whenever the blackout condition is reached you can change the termination mode to stop ray tracing if this occurs For the complex ray tracing technique this occurs when the signal strength reaches zero decibels dB This will help speed up ray tracing sessions by ignoring signals that lose all power 3 3 4 Choosing Ionospheric Models URSI or CCIR PROPLAB is integrated with two different ionospheric models while using the simple ray tracing technique and six ionospheric models while using the complex ray tracing technique These models are discussed below Ionospheric models are necessary in order to describe the characteristics of the ionosphere around the world These models ef
216. solar wind When this occ urs a shockwave not unlike the shockwaves that are formed by supersonic aircraft may form at the front of the disturbance Within 2 or 3 days this material may arrive at the Earth and slam into the Earth s magnetosphere at speeds as high as 7 200 000 kilometers an hour or 4 500 000 miles per hour or 2 000 kilometers per second The magnetosphere res ponds to this sudden increase in solar wind speed and pressure by springing inward or b eing suddenly compressed This can be observed in space and on the ground by magnetometers w hich are capable of measuring the strength of the Earth s magnetic field Compression of our magnetosphere causes the strength of the magnetic field to increase This sudden enhancement in the strength of the magnetic field is known as a sudden impulse or SI When it is associated with the sudden occurrence of geomagnetic storming it is known as a 6 sudden storm commencement or SSC Strong interplanetary disturbances can make it difficult for satellite controllers to control their satellites Uncontrolled tu mbling of satellites can occur Satellite surfaces may be electrically charged to levels which may ca use small discharges within the satellites and thereby damage some of the electronics 2 2 3 Flare Rating System Flares are rated in two different ways The first method was used earlier this c entury and is still in wide use today It involves measuring the brightness of the flar
217. spheric characteristics described in the Section titled Global Ionospheric Maps In fact many of the prompts which must be answered i n that section are also required to produce real time maps Refer to the Global Ionospheric Ma p section for information on how to respond to the various prompts PROPLAB will produce real time maps of ionospheric critical F2 layer frequencies maximum usable frequencies for 3000 km or variable distance paths critical E layer frequencies M factors for 3000 km distances maximum heights of electron densit ies solar zenith angles which are 90 degrees minus the elevation angle of the Sun above the hori zon essentially solar elevation angles and various maps of the Earth s magnetic field PROPLAB will also produce real time transverse plasma frequency maps of the ionosphere between any two points on the Earth This latter map shows you a picture of the ionospheric layers and lets you see how the structure of the ionosphere changes in real time The magnetic field maps are not updated 122 in real time because their parameters change too slowly to observe even over time scales of years For example magnetic latitudes are related to the location of the geoma gnetic poles and the poles only change minutely from year to year Hence mapping the geomagnetic field parameters in real time is not really practical All of the other maps however are updated in real time 11 3 Update Rates for the Real Time Maps
218. st be associated with an infinite number o f imaginary rays that have more substantial differences or vary in characteristics more seriously than the traced ray Each traced ray must therefore be assumed to cover a larger area of ground in order to simulate true conditions realistically As a result if there are a relatively s mall number of traced 103 rays that are used you may have to accept signals that strike the ground within a larger area than just 50 kilometers You might need to accept signals within 200 kilometers o f the receiver For very large numbers of rays the concentration of rays that strike the ground along the great circle path will be sufficient to use smaller values say within 5 or 10 kilometers of the receiver You can experiment with the values but keep in mind that you want to keep this window as small as possible while still retaining a respectable number of samples to build reliable results The next prompt asks you whether you want to analyze all rays regardless of their signal quality In most cases you will want to consider only those rays that are assoc iated with a signal quality above zero in other words one which has not blacked out due to abso rption or other factors This filters out all of the signals that would not be received because they have been degraded to the point of uselessness and displays only those signals that you sh ould be able to hear at the receiver If you re curious about the c
219. straight line until it reaches the ground o ver 3 400 kilometers from the transmission point The last ray traced in the above example is transmitted at an elevation angle of 20 degrees above the horizon It shows that as the elevation angle is increased it becomes increasingly difficult for the signal to return to the Earth through the process of refraction In this case the signal did refract but did not refract enough to return to the E arth 2 6 2 Ionospheric Critical Frequencies and Heights A great deal of information can be discerned through the study of signals that are transmitted and reflected vertically from the ionosphere Ionosondes are used for this purpose There are many ionospheric sounding stations around the world Most of these stations are equipped with radio equipment designed to transmit signal pulses ve rtically and listen for echoes The principles are very similar to those that allow radar guns to work A signal is transmitted vertically into the ionosphere at a specific frequency As the signal passes into the ionosphere it is reflected back to the transmitting station whe re a receiver records the characteristics and time required for the reflected pulse to return The ionosonde then transmits another signal pulse at a slightly higher frequency and listens for the return of that pulse This process repeats in rapid succession with gradually increasing f requencies The frequency is sweeped from low to high frequencies
220. t signal quality is obviously associated with the single hop high frequency signals If our antenna radiates a fair amount of power between about 5 and 8 degrees in elevation angle the 1 hop a propagation mode on a frequency near the E HI HiO FOT 0 85 x MUF of 29 MHz should give the best results However as these figures illustrate you have a fairly wide choice of 2 frequencies before additional modes begin o introducing significant levels of multipathing Frequencies between about 23 MHz and 34 MHz will give good communications Note however that if the MUF is approached too closely severe MUF fading could begin to be observed caused by the intermittent aes ii 2 Ho ii penetration of the signals through the ii A IE E E a E ionosphere A safer choice of frequencies Figure 8 6 Elevation Angle Plot for the path from Texas would be between 23 and 29 MHz to the Eastern U S on 25 Dec 1991 at 18 00 UTC Signal Quality u a O 43 85 LH HA 40 19 a H H 75 00 26 54 22 88 Eep 29 23 25 58 ZH 21 92 P 18 27 14 62 30 00 Lon 100 40 00 Lon OBLIQUE SOUNDING IONOGRAM EAS 3 Hop D ii LHop les ry 7 31 4
221. t is given in units of dB actually dBi or decibels above one microvolt Positive values indicate hearable signals Negative values refer to signals that have ost most if not all power to absorption ground reflections signal spreading etc Ground Range This value represents the ground range of the ray away from the transmitter an d is computed as the great circle distance of the ray from the transmitter It doe s not represent the total geometrical distance that is the total distance the ray travels For this you must instr uct PROPLAB to save ray tracing results to the RESULTS OUT text file The geometri cal distance figure is saved to this file along with other valuable parameters such as group path and polarization Ray Azimuth This value defines the extent to which the currently traced ray is deviating f rom the great circle path in degrees A value of 0 00 degrees means the signal is precisely following the great circle path With this information at your disposal interpreting the results of three dimens ional ray tracings should be easier and more enjoyable 3 4 1 5 The Text File Ray Tracing Results PROPLAB PRO Version 2 0 comes equipped with an option that will save detailed ra y tracing information to a textual disk file named RESULTS OUT The information saved to this file includes the current altitude of the ray ground range phase path group path geometrical path distance that is the total distance travelled b
222. technique ate gradually bends upward because of the Earth s Luss B S78 Bias acess on arinta anida spherical shape The comprehensive technique performs the same computations but speeds up ray tracings by simply p lotting a straight line to the location where the ray penetrates into the ionosphere This is why the base part of the ray paths may appear a bit discontinuous It does not affect the acc uracy of the tracings at all Notice how these two rays the ordinary and extraordinary rays each travel inde pendent paths through the ionosphere Notice also how the ordinary ray undergoes a chord al reflection over the equatorial region on its second hop before it returns to the ground The extraordinary ray also experiences a chordal hop on its second hop However unlike the ordinary ray the extraordinary ray becomes trapped between the E and F layers in a process called ducting Ducting is quite common and can result in extremely long signal paths if the geo metry is right Signals that are ducted tend to have a whispery tone to them but in many cases the signals remain quite intelligible The three dimensional grid shown above should be viewed as follows Imagine the base of the grid where the transmitter and receiver reside forms the inside of a box with only two sides In the above example the far side of the box forms the altitude wall This wall shows the altitude of the traced rays in the ionosphere The right side of the box
223. ted to save the screen image to the GIF image file IONOGRAM GIF You can then use GIF image viewing software to view the sav ed image The image will be saved according to the parameters established within PR OPLAB s option menu Main Menu option 8 suboption 17 Press P after PROPLAB has finished plotting the ionogram to save the screen im age in a PostScript compatible format for sending to a laser printer Press H after PROPLAB has plotted the ionogram to print the graphic screen to your printer You must first edit the text printer control file PROPLAB PTR before this function will work for your particular printer Pressing any other key will return you to PROPLAB s Main Menu To re examine or redraw the ionograms using different parameters choose Main Menu option 1 su boption 4 Generate Oblique Sounder Ionogram and at the prompt to Analyze previously generated ionogram data select Y This will transfer control back to the ionogram ana lysis utility and will let you reconstruct a new or different ionogram using different parameters SECTION 9 COMPLEX AREA COVERAGE MAPS Using the Complex Ray Tracing Technique We use the term complex area coverage maps to denote area coverage maps that are created from results of comprehensive or complex ray tracing sessions that is sessions which use the complex ray tracing technique It does not allude to the complexity of the maps Producing area coverage maps using the res
224. ter and receiver It then selects the lower of these two MUFs PROPLAB does not rigorously ray trace through the entire length of the path when computing long distance MUFs Nor does it consider effects of sporadic E on the MUF The o blique ionogram technique used to produce Figure 8 1 does rigorously ray trace througho ut the entire 106 length of the path It makes no assumptions or estimations by limiting the analy sis to two control points And it will consider the effects of sporadic E on the MUF For this reas on you can determine actual MUFs between any transmitter or receiver using these plots It is possible to reanalyze propagation conditions at any distance between the t ransmitter and receiver by changing the location of the receiver when so asked The first q uestion posed by the PROPLAB Oblique Sounder Ionogram utility SOUNDER EXE is Change Receive r Location By responding to this question with Y you are asked to type in a new distance to the receiver Figure 8 2 shows the results of a reanalysis between Hawaii and a point at about 36N 126W off the California coast This was done by changing the distance between t he transmitter and receiver from 5 300 kilometers to 3 500 kilometers Notice that we are still analyzing conditions along the same great circle path but at a different distance from the transmitter E The results shown in Figure 8 2 differ substantially from those depicted in Figure 8 1 First notice t
225. tered in decimal notation not in degrees mi nutes and seconds notation That is if your geographical location is 50 degrees north latitude 30 minutes and 45 seconds you would enter your geographical position as 50 5125 not as 50 3045 In addition all latitudes north of the equator must be entered as posi tive numbers while those latitudes south of the equator should be entered as negative numbers Geographical longitude values can be measured in decimal degrees west or east of Greenwich For example Denver Colorado is located at approximately 105 degrees west longitude and would therefore be entered in PROPLAB at a position of 105 degrees Again decimal values must be used not degrees minutes and seconds Sydney Australia is located at 150 degrees east longitude or 210 degrees west longitude If measurements are given in degrees east of Greenwich negative values must be used That is if Sydney s ea stern longitude value were entered in PROPLAB the value 150 would be used PROPLAB requires knowledge of the time zone of the transmitter so that if local time is used PROPLAB can compute what the local time is at the receiver PROPLAB has the ability to automatically guestimate the time zone of the transmitter by dividing the geographical longitude of the transmitter by 15 degrees since the Sun travels 1 5 degrees of longitude per hour Although this is usually accurate enough some regions may not be in easily divisible time zones PROPL
226. the Sun appears directly overhead at 12 noon Because of the orbit of the Earth arou nd the Sun this angle varies by about 23 degrees At the seasonal equinoxes spring and fall the solar declination angle is about zero degrees Therefore during these times the Sun would appear directly overhead at noon over the equator The third line gives you the magnet ic latitude and longitude of the geographical position used in the profile statistics The geographical position of the profile statistics is given in the second line of the display after the Profile Location The final line of this display shows you the magnetic DIP or inclination angle at the current geographical profile location To return to the PROPLAB Main Menu press the ENTER key 3 4 7 Quitting PROPLAB and returning to DOS To leave PROPLAB s Main Menu and exit to the DOS prompt simply select the twelf th option of the Main Menu or press the ESCape key SECTION 4 GLOBAL IONOSPHERIC MAPS A substantial amount of PROPLAB s power lies in its ability to generate practica lly any type of map for almost every type of ionospheric parameter relevant to radio com munications The maps resemble weather type maps and use complex contouring algorithms to pro duce contours of equal values By selecting the fifth option of PROPLAB s Main Menu you gain access to this large base of power This section will describe the available typ es of maps that can be generated and how they can be
227. the above prompts apply mostly to three dimensional ionospheric models Two dimensional models are not quite as demanding as only a single profile file is built by the name of IRIPROF DAT in the main PROPLAB directory The prompt asking whether or not to delete existing profiles does not apply when two dimensional models are used and should be answered with a N o meaning you don t want to delete any existing 3 D profiles Following these prompts PROPLAB begins to automatically compile the required pr ofiles in the PROFDATA subdirectory for 3D profiles or in the main PROPLAB directory f or 2D profiles After it finishes building the profiles it automatically loads the r ay tracing engine and begins comprehensively tracing the signals through the ionosphere 3 4 1 3 Understanding the Generation of Ionospheric Profiles The comprehensive ray tracing technique differs from the simple ray tracing tech nique in that it cannot compute the characteristics of the ionosphere on the fly as the simple method can The reason has to do with memory constraints The comprehensive ray tracing engine is an exceptionally complex and large software program In order to fit it all into me mory some desirable features had to be removed such as the ability to compute on the fly ionospheric profiles We could have used overlays to add this ability but the use of overlays would have dramatically decreased the performance and speed of the ray tracing engine Future
228. the flare is observe d indicating that the CME is responsible for triggering the flare A major type of CME which is often observed are known as disappearing filaments or DSFs Strings of material are often observed floating above the surface of the Sun These ropes of gas are suspended above the surface of the Sun by magnetic fields This process results in the cooling of the gas which makes it appear darker than the brighter and hotter photospheric surface When observed on the limb the suspension of the g as above the surface of the Sun can be clearly discerned and the gas is luminous against the darker background of space Occasionally one or some of the magnetic fields suspendi ng the gas above the solar surface may break free from the surface This may cause the gas to begin erupting upward and outward from the Sun This is known as an erupting filament Some very impressive erupting filaments have been observed as limb events on the Sun When observed against the brighter photospheric surface the dark string of material within the erupting filament simply disappears From this follows the term disappearing filament Filaments and other coronal mass ejections related to the more energetic solar flaring processes are capable of spewing out mass from the Sun that may quickly travel the large distance from the Sun to the Earth These disturbances are often travelling at s peeds significantly greater than the background speed of the
229. the great circle line The key below the grid shows numerous statistics which will be of interest durin g the tracing of signals The information displayed is explained below Ray Type Gives the type of ray ordinary or extraordinary that is currently being trac ed Ordinary rays are colored white Extraordinary rays are colored yellow Elev Angle Defines the elevation take off angle used by the transmitting antenna A value of 0 00 degrees indicates PROPLAB is tracing a ray that was originally shot at the horizon Azimuth Lists the azimuth that was used at the transmitter for the current ray being traced A value of 0 00 degrees indicates PROPLAB is tracing a ray that was directed direc tly northward by the transmitter It does not indicate the current azimuth of the ray see the bearing below Frequency Gives the frequency of the ray currently being traced in MHz Local Eley This section defines the elevation of the wave normal of the ray with respect to the horizontal A value of zero degrees means the ray is travelling exactly horizontal Positive values indicate the ray is travelling upward at the specified angle Negative va lues indicate the ray is travelling downward toward the ground at the specified angle This value is continually updated as the ray is traced through the ionosphere Ray Lat and Ray Lon These values identify the current geographical location of the ray being traced through the ionosphere Positive latitude
230. the ionosphere and esc apes into space Critical frequencies are very important in the study of radio propagation They are used to determine maximum usable frequencies for obliquely propagated radio wave s and can be used in many other ways to help determine other ionospheric quantities as well as the general condition of the ionosphere Each ionospheric layer the E Fl and F2 layers has its own critical frequency Since the maximum electron density usually occurs in the F2 layer this layer is usual ly used to determine the maximum usable frequency or the frequency beyond which signals pe netrate the ionosphere altogether The critical frequency of the E layer is denoted foE Similarly the critical frequencies of the F1 and F2 layers are denoted foF1 and foF2 It is important to remember that a critical frequency always refers to signals that are directed st raight up toward the zenith Another frequently used term is the plasma frequency which is simply the critical frequency of a section of ionospheric plasma This is discussed in grea ter detail later Each ionospheric layer critical frequency occurs at a specific height that varie s throughout the day For example the critical frequency of the E layer usually resides near 105 kilometers in height while the critical frequency of the F2 layer lies betw een approximately 240 and 350 kilometers in height Since the critical frequency ref ers to the location where maximum refraction occurs
231. the results of the propagation delay plot for this path Immediately several important parameters can be determined the number of supported modes the MUF of each mode and the LUF 20 of each mode There are four supported 1 s o modes of propagation 1 hop 2 hop 3 hop 0 08 and 4 hop modes The MUF s of each of fis these modes are 34 25 MHz 22 5 MHz ss 17 25 MHz and 14 75 MHz respectively 2 5 Similarly the LUF of the 2 hop mode is 5 25 3c MHz the 3 hop mode is 6 5 MHz and the 4 22 PSS er Pe et PET Le re ERRE AUNE i o Signal Quality 00 75 00 30 00 Lon io 40 00 Lon OBLIQUE SOUNDING IONOGRAM 1 Hop 8 63 mae ava PEEL AT Geer REPT hop mode is 8 0 MHz The LUF for the 1 Sio es er ue Ba eT Ait Be eo ws 40 0 hop mode from this figure is difficult to Figure 8 5 Propagation Delay Plot for the path from determine since the traces for the 2 hop mode Texas 30N 100W to the Eastern U S 40N 75W a distance of 2 520 km on 25 Dec 1991 at 18 00 UTC intermix with the 1 hop mode and cannot be discerned in these black and white renditions of the display screens Suffice it to say that the 1 and 2 hop modes have similar LUFs in the lower HF band near 5 MHz
232. ther Minimum critical frequencies are observed around local midnight with foE values of about 0 4 MHz It is important to keep in mind that foE is dependent upon sporadic E and enhanc ed nighttime E layer ionization perhaps caused by auroral electron precipitation etc Sporadic E can increase foE by many times For example normal nighttime foE is around 0 4 MHz A 5 MHz sporadic E critical frequency would increase the nighttime foE value for aff ected regions 80 to 5 MHz which is a factor of 12 5 times greater than the normal nighttime foE value These contoured maps of critical E layer frequencies do not take these sporadic phenom enon into consideration even if they are identified with PROPLAB as regions of sporadic E Only the regular non deviative foE values are used in these plots 4 6 Producing Maps of Solar Zenith Angles These types of maps are exceptionally valuable when determining possible effects of solar flares on signal paths Maps of solar zenith angles show the elevation angle of the Sun away from the zenith or the point straight up overhead A solar zenith angle of zero degrees corresponds to the point exactly straight up overhead A solar zenith angle of 45 degrees corresponds to a point half way between the horizon and the zenith Similarly a solar zenith angle of 90 degrees corresponds to a point directly on the flat horizon Solar zenith angles of 90 degrees therefore denote areas of the world that are undergoing eithe
233. there is a gap or void where no signals will be received from one hop signals even with low angles of elevation between about 14 25 and 16 MHz Two hop signals can only be received if the angle of elevation at the trans mitter is between about 11 and 17 degrees above the horizon Notice how only two hop signa ls will be 109 received between 14 25 and 15 25 MHz as these are the only traces present Between 15 25 MHz and 16 0 MHz no signals are receivable at the ship Both single hop and dua l hop paths fail to reach the transmitter between these frequencies With this information in hand you can determine what angles of elevation to use to exploit communications to remote locations using specific numbers of hops You can also determine to some degree what type of antenna radiation pattern should be used For example for reliable single hop communications a very directional and narrow beam antenna will be required so that most of the radiated energy is emitted at angles of elevation less than about 4 or 5 degrees Since most antennas in use today have a broader radiation pattern it is reasonable to think that a fair amount of energy will be lost if only radiation angles betw een about 0 and 3 degrees reach the desired receiver in one hop Such antennas are also more expensive and a bit more difficult to build It might therefore be to your advantage to concentr ate on 2 hop paths to the receiver where the range of elevation angles required to re
234. thod The Runge Kutta method is slower than the Adams Moulton method but produces a prodigious amount of information if you have instructed PROPLAB to save the ray tracing results to the text file RESULTS OUT You can choose to use either of these two methods however the Adams Moulton method tend s to be slightly faster and perhaps only marginally more accurate than the Runge Kutta method The Adams Moulton method is the default integration method 3 3 18 6 Display Method There are five available ways in which PROPLAB PRO displays ray tracing results while using the comprehensive ray tracing technique They are described below The first method does not graphically display any ray tracing information on screen It instead simply computes the ray tracing paths numerically and saves the results to the file RESULTS OUT if and only if you tell PROPLAB to create this file when you are answering the prompts that define the elevation angles to use etc While PROPLAB is compu ting the ray paths nothing will be displayed You may therefore think PROPLAB has crashed yo ur computer depending on the length of time required to complete the ray tracings This method is not recommended as it does not graphically show you any ray tracing results But it might be useful for those who are only interested in numerical results The second display method graphically displays rays traced through the ionosphere by assuming you are looking at the ray cross ways fr
235. ts that can reflect the diverse conditions in the ionosphere 22 2 6 6 Skip Distance and Maximum Usable Frequency When tracing rays through the yao pone mata a ionosphere it is useful to have an ee 5 understanding of skip distances and 7 maximum usable frequencies Often people 8 Risi te esor confuse maximum usable frequencies with penetration or critical frequencies For obliquely propagated radio waves maximum usable frequencies are not equivalent to critical frequencies Aur Dist 0 0 Iono Dst 1676 0 Consider Figure 2 5 in the following discussion This figure shows a typical situation where for a given frequency the 1000 kooo elevation angle is increased so that the Figure 2 5 MUF and Skip Distance signal eventually penetrates the ionosphere Notice that as the elevation angle is increased the distance between consecutiv e rays begins to decrease Moreover as the elevation increases the ground distance between the transmitter and the receiver decreases If the elevation angle is further increased at regul ar increments it can be seen in Figure 2 5 that a point is reached where the signal no longer hits the ground at decreasing distances but rapidly increasing distances The point where the dist ance changes direction from decreasing to increasing is known as the skip distance It is interesting to note that another side effect of this phenomenon is the increasing concentration of rays as the skip distance is appr
236. tude it may be useful to know where a signal travels in relation to magnetic latitude This option gives you the ability to map magnetic latitude 4 10 Producing Maps of Modified DIP Angles PROPLAB uses in addition to the regular DIP angle calculations a modified DIP angle equation that is more accurate in determining certain ionospheric characteristic s This option lets you map the modified DIP angles 4 11 Transverse Plasma Frequency Maps An exceptionally powerful and useful map available with PROPLAB is the transvers e plasma frequency map Imagine slicing the ionosphere vertically with a knife and looking at that sliced portion edge on This is what the transverse plasma frequency map provides It is analogous to cutting a tree down and examining the internal rings What you see in a transverse plasma frequency map is a cross section of the ionosphere the actual internal structure as it varies with height Why is a transverse plasma frequency map so valuable Because it shows you where ionospheric tilts exist that can cause non great circle propagation It shows yo u the various layers of ionization in the ionosphere and gives you information on their locations in tensities etc For 82 example Figure 4 3 is a hypothetical cross section of the ionosphere for the path between northern Mexico and eastern Australia at 19 00 UTC on 15 July 1994 using a sunspot number of 100 and an A index of 5 The transmitter is at the far left o
237. ue to the decreased night time electron density present at the second hop location For this reason the MUF for the 3 500 kilom eter path to 36N 126W is higher than the MUF for the path to Colorado Notice also that the various modes of communication are better defined in Figure 8 2 There are also a greater number of rays received throughout the frequency range plotted which improves the visibility of certain features in the plot The overall signal qual ity is also higher Referring to Figure 8 2 you can determine the MUF for signals of any number of specific hops For example it was already shown that the 1 hop MUF was about 23 5 MHz S imilarly by examining the maximum frequency on the ionogram in Figure 8 2 for 2 hop signa ls it can be seen that the 2 hop MUF is about 15 25 MHz Similarly 3 hop signals are asso ciated with 107 an MUF of about 11 5 MHz 4 hop signals with an MUF of 9 5 MHz 5 hop paths with an MUF of 5 25 MHz and 6 hop paths with an MUF of about 2 75 MHz Since signals are us ually focused and become stronger near the MUF you can expect signals with multi hop MUFs to be stronger than might normally be expected However signals which have multiple g round hops also lose signal strength due to ground absorption and multiple ionospheric cros sings they might therefore be weaker than single hop signals With this information in mind consider what communications might be like along the 3 500 km path depicted in Figure 8
238. ultipl ied by the frequency v w x f when the speed of light is less than the speed in a vacuu m c the wavelength of the light is also correspondingly reduced Thus the wavelength of light in a material is less than the wavelength of the same light in a vacuum Rays which strike a surface such as water at a shallow angle might not experienc e any refraction at all For every refractive material there is an angle known as the critical angle where total internal reflection occurs This process can be important in radio c ommunications where signals may for example strike a highly dense sporadic E layer and exper ience total reflection Rays which strike the material at angles of incidence smaller than the critical angle are refracted while rays which strike the material at angles larger than the critical angle are totally reflected The idea of total internal reflection can be understood by examining what happens when light passes through a Porro prism see Figure 2 1 A Porro prism is a triangular slab of glass When light passes perpendicularly through one of the prisms sides the ray of light does not change direction but passes undeviated straight into the glass However when the light reaches the other side of the prism it strikes that boundary between the air and the glass at a 45 degree angle For a glass air boundary the critical angle is 42 degrees Since the angle of incidence at this boundary is larger than the critical angle
239. ults of complex ray tracing sessions is really quite easy to do To display area coverage or broadcast coverage maps when using the comprehensi ve ray tracing technique to trace rays select Main Menu Option 6 and select the C omprehensive method 114 The comprehensive broadcast coverage map generating utility is completely differ ent from the software used to generate the simple broadcast coverage maps This is primar ily because the complex ray tracing technique produces signal strength results as opposed to the signal quality values that the simple technique produces Before a broadcast coverage map can be displayed data must obviously be collect ed by performing a ray tracing session that uses the comprehensive ray tracing technique This is accomplished by first setting up the appropriate parameters in the Comprehensive Options Menu Main Menu Option 8 Suboption 18 with emphasis on Choice 21 and then initi ating the comprehensive ray tracing function through Main Menu Option 1 For best results the option supporting the ability to ray trace signals by swee ping elevation angles and frequencies and azimuths should be used because this allows you to sweep in two directions in elevation and across in azimuth which simulates realistic transmissions However if you are only interested in single azimuths you can produce results by sweeping only elevation angles which keeps the azimuth constant This has the advantage of s howi
240. unication The unique ability of the ionosphere to bend and reflect radio waves has been a topic of heavy study for decades Over the many years since we began studying the ionosphere w e have learned a great deal about the characteristics and true nature of the ionosphere Many books have been devoted to this subject Over the last 20 years computers have been used with ever increasing frequency to study the effects of radio signal refraction or the bending of radio waves w ithin the ionosphere In the last 10 years personal computers have become significantly m ore powerful and capable of performing the complex functions necessary to analyze the ionosphere in relative detail It is then no wonder that we have made many of the major strides in the field of ionospheric radio propagation in this same period of tim e There are many computer programs presently available for predicting such quantit ies as the Maximum Usable Frequency or MUF great circle paths or the path travel led by a radio signal from one location to another and graylines or the regions where the Sun is either rising or setting Several of these have advanced features such as the a bility to compute signal strengths between two points or optimum times of transmission PROPLAB PRO contains all of these features and many others which have previously only been found on the larger main frame computers available to researchers and scientists For example PROPLAB PRO is t
241. urs of maximum usable frequencies and or contours of maximum F2 layer heights and or contours of solar zenith ang le and or with broadcast coverage maps etc The end result could be a screen image loaded with invaluable information 3 4 4 Setting up Transmitter and Receiver Locations The third option of PROPLAB s Main Menu gives you the ability to define regions of sporadic E or transmitter receiver geographical positions Select the latter by pressing X followed by ENTER Setting up the transmitter and receiver locations has been de scribed in detail in Section 3 3 2 Refer to that section for more information After you have defined the transmitter and receiver locations press the ESCape key on your keyboard to return to the PROPLAB Main Menu 3 4 5 Plotting Electron Density Profiles The fourth option of the Main Menu will plot electron density profiles for any S INGLE HOP path MIDPOINT specified The midpoint is defined as that point that lies half way between the transmitter and receiver on the great circle path If the great circle distance exceeds 4 000 kilometers only the profile for the midpoint of the FIRST HOP is used This is useful for determining ionospheric conditions at any path midpoint To determine conditions at the 71 transmitter geographical location set the receiver geographical position to the transmitter position so the path midpoint lies over the transmitter location For example if the transmitter was locat
242. used You retain full control over how you want the maps generated right down to the color for the contour lines All of the different maps require you to enter specific common information the date time sunspot number geomagnetic A index or press ENTER if not available sunspot n umber map 74 resolution level type of map projection to use type of map to generate contour specifications ionospheric model to use and the contour color to use The date time sunspot number geomagnetic A index and type of map to generate are self explanatory inputs and need no further discussion The others need to be ex plained in slightly greater detail before reliable use of these powerful functions can be e xpected For each map generated you will be asked to select a map resolution level This determines how spatially accurate the map is for the given date and time etc There are five different resolution levels that can be selected The lowest resolution level produces maps much quicker than higher resolution levels but the spatial accuracy of the map may be lacking In other words some features that may be present might not be shown in the lower r esolution maps The resolution level varies according to the type of map projection you select For example the spatial resolution and accuracy of a global Lambert map projection can be approximately doubled if a polar map projection such as an orthographic project ion is used Why Simply bec
243. uture collected data to the database of results 8 3 Phase 2 Analyzing the Results After PROPLAB has finished the data collection phase the utility program SOUNDER EXE is loaded and executed This utility reads the results from the da tabase file CHIRP OUT processes the data and displays the results on screen This utility can be optionally run from the DOS command line after the database has been built Provided the database file CHIRP OUT exists and contains data PROPLAB will di splay the geographical location of the receiver as well as the great circle distance to the receiver and ask you if you want to change the location of the receiver Since PROPLAB ray tr aces through the ionosphere a profile of propagation conditions can actually be computed any where between the transmitter and receiver provided the chosen location lies along the same g reat circle path If you choose to change the location of the receiver you will be asked to type in a new great circle distance to the receiver This distance is then later converted into appr opriate geographical coordinates and are displayed along with the final results You cannot specify a new receiver 102 location beyond the distance of the receiver used during the ray tracing phase It must lie between the transmitter and the receiver If you do not wish to alter the location of the receiver press ENTER or type N and press ENTER This will give you the second prompt which asks
244. vailable options apply to only one of these techniques Others apply to both It is important to know which options apply to which techniques so that PROPLAB is appropriately set up 25 SECTION 3 PROPLAB The file README NEW which is installed with PROPLAB may contain information that is not contained in this manual Consult that file for information not appearing in this manual 3 1 Installation of PROPLAB To install PROPLAB on your hard drive insert the program code disk into drive A and type A INSTALL After supplying any necessary information PROPLAB will b egin installing the software in the directory C PROPLAB on your hard drive Part of the installation procedure includes generating maps centered on your particular geog raphical position Each of these differing maps can be used by the PROPLAB software In order for some of the functions of PROPLAB to operate properly it is imperative that you install at least one map a Plate Carree map must reside in your map library for these func tions to work IMPORTANT PROPLAB PRO Version 2 0 will now construct full color global maps where the ocean is colored blue and the land is colored brown with large lakes dso colored blue This new enhancement provides aesthetically pleasing maps compared to themono color maps used in previous releases If you do not want to use these new full olor maps but would rather stick with the older style maps use the older map management tility on you
245. values between two geographical points The level of signal degradation is dependent on signal power and perhaps more importantly signal frequency Higher freque ncies experience less absorption than lower frequency signals during PCA However hig her frequencies also penetrate the refracting ionospheric layers more easily than lo wer frequencies If propagation through the polar regions during PCA is required it may therefore be wisest to use high transmission powers on frequencies close to the maximum usable frequenc y PCA does not significantly alter the refractive nature of the ionosphere Since most of the ionization and absorption associated with PCA occurs below the E region which is the first major refracting layer of the ionosphere most signals still refract in the same manner as would occur if PCA was not present PCA follows a diurnal pattern Polar cap absorption is strongest during the day and weakest at night However the difference between daytime absorption and nightti me absorption is small only about 2 dB If PCA is relatively strong ex above 4 or 5 dB this difference in daytime and nighttime absorption levels may not be significant eno ugh to give any better signal performance 2 6 Ionospheric Radio Propagation Most ionospheric disturbances have degratory effects on radio communications However this is not always true For example strong signal absorption during a major flare may completely absorb HF signals and e
246. ved from the Earth The second rating system is less subjective and depends on the measured brightne ss of the soft xray emissions in the wavelength band 1 to 8 Angstroms as observed by Earth orbiting satellites such as GOES 6 and or GOES 7 Geostationary Operational Envi ronmental Satellites or GOES This system was initiated on 01 January 1969 and ranks so lar activity by its peak x ray intensity This classification method offers two distinct adva ntages compared with the standard optical classification system it gives a better meas ure of the geophysical significance of solar activity and it provides an objective means of classifying geophysically significant activity regardless of its location on the solar disk or near the solar limb This rating system is described as follows all x ray measurements are in Watts per square meter A Intensity lt 10 7 lt Intensity lt lt Intensity The letter designates the order of magnitude of the peak x ray value observed T he number following the letter is the multiplicative factor For example a M3 2 ev ent indicates an x ray burst with a peak flux of 3 2 x 10 Watts per square meter Wm The PROPLAB software will accept as input the peak magnitude of the x rays observed during solar flares to compute circuit quality during flare activity The flare rating system which should be used is this one employed for soft x rays above Sources for this information are
247. veral rays may straddle the receiver hitting the ground p erhaps only a few tenths of a kilometer or a few kilometers from the receiver location To solve t his situation we must assume that each transmitted ray represents many individual rays with sligh tly differing characteristics slightly different elevation angle of transmission slightly different frequency etc If we make this assumption which is true enough we can expect that for each t raced ray which hits a specific location there will be an infinite number of imaginary rays which strike the ground at slightly differing locations from the principal traced ray All will strike the ground a few tenths of a kilometer or a few kilometers on either side of the traced ray effe ctively eliminating all gaps present If we use this theory and reasoning then this prompt makes sense We are in es sence saying that if a traced ray strikes the ground within say 50 kilometers of the receiver then an associated imaginary ray has actually arrived at the receiving antenna with c haracteristics close enough to the traced ray that the two rays the imaginary ray and the traced ray can be considered the same As a result all rays that reach the ground within 50 kilometers of the receiver are assumed to have been received by the receiving antenna and are proc essed If you collected data using relatively large step increments there will be relatively few traced rays implying that each ray mu
248. ween labelled tic ks on the distance scale For example if the transmitter receiver distance is 7 000 kilometers and you want PROPLAB to display labelled tick marks or lines every 1 000 kilometers toward the receiver you would specify 1000 here This lets you instantly estimate the ground locatio n and distance the rays are from the transmitter during the ray tracing phase The last prompt defines the lateral distance grid Since traced three dimensional rays can deviate away from the great circle path the lateral distance grid gives you the ability to define how large this lateral deviation grid should be The Figure beside this paragraph illustrates this further The line drawn length wise down the center of the grid in this Figure defines the great circle distance between the transmitter and 48 receiver which are located at the ends of the A line The distance grid runs along the length of the A line The lateral deviation grid distance is the distance represented by the B line Rays which deviate away from the great circle path will begin to turn away from the A line and begin crossing through a portion of the distance represented by the B line The last prompt in this option defines how far across the B line should span in kilometers By making the distance smaller you are able to discern smaller lateral changes in the traced rays By making the distance larger you are able to discern larger lateral deviations in traced ra
249. where the ionospheric layers have increased in height by about 50 to 100 kilometers For signals striking these ionospheric layers at the appropriate angles chordal hop type propagation may be possible due to the tilting of the ionosphere on both sides of the equator In this case the magnetic equator is located at approximately the 5 000 km mark PROPLAB will produce transverse plasma frequency maps or cross sections of the ionosphere for any signal path You simply specify the geographical locations of the transmitter and receiver and tell PROPLAB how high up to 1 000 km in the ionosphere to map and PROPLAB will do the rest For greater accuracy on very long paths such as the one from Mexico to Australia divide the path into segments and generate transverse maps for each of those segments The spatial resolution of the maps is dependent on the distance between the transmitter and receiver For example the ionospheric electron density profile for a 12 000 kilometer path is determined approximately every 500 kilometers whereas the ionospheric electron density pro file for a 4 000 kilometer path is computed approximately once every 170 kilometers giving a hig her level of spatial resolution in the map You can approximate the interval used to determine profiles by dividing the path distance by about 24 For example a 12 000 km path divided by 24 gives a spatial interval of about 500 km A word of caution is required when generating transvers
250. y tracing technique can only reliably handle single hops because only one two dime nsional ionospheric profile is generated On subsequent hops using the two dimensional m odel the same ionospheric profile is used which represents the characteristics of the ionosphe re at the midpoint of the first hop Subsequent hops therefore use the same ionospheric profile which differs from reality For multi hop paths use one of the three dimensional models below Model 2 URSI Three Dimensional Model This model is based on the URSI ionospheric model and describes the ionospheric characteristics in three dimensions up to 1 000 kilometers in height This model or another three dimensional model should be used when accuracy is important when chordal hop propagation or ducting is to be analyzed or when there may be more than one gro und reflection on the way to the receiver Model 3 CCIR Two Dimensional Model This model is based on the CCIR ionospheric model and has the same limitations a s those that describe Model 1 Use the CCIR Three Dimensional Model for multi hop paths chordal hop paths ducting etc Model 4 CCIR Three Dimensional Model This model is the three dimensional version of the CCIR ionospheric model and is identical to Model 2 except it uses the CCIR method of computing ionospheric c haracteristics Model 5 Quasi Parabolic Two Dimensional Model This model is very similar to the ionospheric profile models employed by othe
251. y When PROPLAB has finished drawing contours the box disappears and a label identifying the type o f map completed is printed on the screen You can then press the S key to save the screen imag e for integration in other functions or for superimposing other contours on the same map You can also press the G key to save a copy of the screen image as a GIF image file Or you can pres s the P key to save the screen image in a PostScript compatible file for printing to a laser printer 4 1 Global Maps of Critical F2 Layer Frequencies These very useful maps provide you with instantaneous information regarding worl d wide critical F2 layer frequencies A sample map is shown in Figure 4 1 This Figure was produced by PROPLABs CONTOUR EXE utility invoked by Main Menu Option 5 and is exceptionally valuable for radio communicators It shows you the critical frequencies of the F2 layer throughout the world at a specific date and time level of geomagnetic activity and sunspot number Using the information from this map it is possible to determine where horizontal gradients exist in the electron density profile that might cause non great circle propagation It is also used to determine maximum usable frequencies the general state of the ionosphere etc 272 252 232 212 152 132 112 092 a
252. y reflected signal to make more than one ground hop to reach the d estination This option lets you define exactly how many hops are permitted when ray tracing sign als If you hit ENTER at this prompt PROPLAB will automatically permit as many ground reflection as necessary for the signal to reach the destination Once the destination has been reached or surpassed no more ground hops are permitted If you enter a value at this prom pt that value will be used as the maximum number of allowed hops As soon as the number of hop s reaches this value tracing for that particular ray stops 3 3 13 Selecting PROPLAB s Quick or Normal Modes This option is only valid when using the simple ray tracing method When tracing signals through the ionosphere using the Normal Mode the upper information panel is continually updated as the signal is traced from the transmitter to the receiver When the software is running in the Quick Mode the upper information panel is not updated Only the simultaneous electron density curve is updated in this mode T his has two major effects it reduces the number of calculations and time consuming screen u pdates and it significantly speeds up the tracing of the rays without sacrificing accuracy One major disadvantage of using the Quick Mode is the loss of the computation of signal qu ality Functions 39 that rely on signal quality data such as the generation of Broadcast Coverage S ignal Quality Maps will not work prop
253. y that hits the ground where the arrow points This fre quency differs from the penetration frequency by about 1 0 MHz for as Figure 2 7 illustrates the penetration frequency occurs at about 14 0 MHz The high angle rays are those which would be reflected by the ionosphere between the MUF of 13 MHz and the penetration frequency of 14 MHz 2 7 Ray Tracing Techniques PROPLAB PRO Version 2 0 is equipped with two major ray tracing techniques that 24 compute how signals propagate into and through the ionosphere These two methods will hereafter be called the simple and comprehensive or complex ray tracing techniques The simple ray tracing technique is faster than the comprehensive method but is much less accurate Nevertheless it produces statistics which are of fundamental imp ortance such as the distance the signals travel through the auroral zones the behavior of si gnals as they interact with regions of sporadic E and much more This method does not include effects of the Earth s magnetic field or the process of electron collisions with neutral particles in the atmosphere a very important parameter for determining ionospheric absorption and accurate ray paths However it does estimate the effects of geomagnetic activity on rad io signals The comprehensive ray tracing method is a sophisticated and extremely powerful r ay tracing engine that should be used to accurately trace signals through the ionos phere It will if desired
254. y the ray absorption doppler if any polarization both real and imaginary parts the local elevation angle of the w ave normal component of the ray with the horizontal the elevation angle of the ray as meas ured with respect the transmitter the azimuthal deviation of the ray away from the great circle p ath and the current azimuth from the transmitter to the ray location This information almost completely describes the characteristics of the traced rays 66 Caution should be exercised when saving data to the text file The size of the file can quickly increase depending on the type of ray tracing being performed A single long distance traced ray can result in a text file exceeding 50K bytes Complete ray tracing s essions saved to disk may end up exhausting disk space However it is the only method that provi des complete snapshots of traced rays as they are travelling through the ionosphere 3 4 2 Computing MUFs between any two points This option makes use of the simple ray tracing technique only Automatic computation of the MUF using the comprehensive ray tracing technique is currently beyond the capability of PROPLAB as it would require three dimensional homing capabilities an extremely difficult and time consuming process particularly if done in three dimensions Perhaps it will be attempted in future versions of PROPLAB The second option of the Main Menu lets you compute MUFs for any distance You are requested to enter the
255. y tracings It will be slower than the ot hers due to the increased number of complex computations that must be performed but the ability to trace extraordinary rays as well as the added accuracy of the tracings is more important than the increased computation time 3 3 18 2 Magnetic Field Model This option lets you define the type of model to use to describe the Earth s mag netic field Several models are supported but only one will likely be used for those with se rious applications The first choice of this suboption specifies that no magnetic field should be used If this option is selected the type of ray tracing model selected see Section 3 3 18 1 should correspond to a model that does not require a magnetic field The second choice is the default and recommended choice for those who are concer ned about accuracy This choice selects a standard dipole field model This model cl osely resembles the actual shape and intensity of the Earth s magnetic field and will produce the best results for most applications The third choice selects a model that assumes the DIP angle of the magnetic field is constant The gyrofrequency of this model also increases as the cube of the distance This model will produce unrealistic results unless the user is familiar with appropriate applic ations for this model The fourth choice selects a model that assumes a constant DIP angle and a constant gyrofrequency regardless of the location of the traced ray
256. y using varying ratios of Red to Green to Blue For example you cou ld change the color of YELLOW to a custom color using an example RGB value combination of 14 48 36 The changes you make to the colors of PROPLAB are reflected in all of the module s of PROPLAB including the Map Management System MAKEMAP EXE So if you want to recreate your map database using different map colors you simply need to exe cute PROPLAB via PROPLAB SETCOLORS and then change the RGB values of the appropriate map colors For example to make the oceans a GRAY color instead of blue you would change the RGB value for the color BLUE to an RGB combination such as 40 4 0 40 Then rerun the MAKEMAP EXE utility to reconstruct the desired maps using the new color Keep in mind that the all other PROPLAB modules that use the color BLUE will now use the color of GRAY instead So the colors you change may have side effects with he colors used in other sections of PROPLAB Some of the subprograms within PROPLAB are large For this reason the PROPLAB EXE program basically controls the main functions of PROPLAB sets up the relevant parameters contains the main menu and submenus and redirects control to the other subprograms when appropriate Most of the functions in PROPLAB are computation intensive and require at least a 386 computer to operate at a decent speed However even some 386 based systems ex those without math coprocessors may operate relatively slowly while u
257. you to accept signa Is that reach the ground within how many kilometers of the receiver In other words it as ks you to specify how closely signals must approach the receiver location before they are accepted as having actually reached the receiver This is an important prompt and deserves further explanation In reality radio transmissions are composed of an infinite number of rays that travel individually through the ionosphere As a result the reflected radio energy hit s the ground at an infinite number of points along the great circle path towards the receiver You can therefore sample almost any location along the great circle path and measure signal energy reaching the ground The same does not apply to PROPLAB Since PROPLAB must individually trac e each ray through the ionosphere it is not practical to permit an infinite number of rays To speed up the procedure it is necessary to limit the number of rays that are traced throu gh the ionosphere If a significant number of rays are traced the results will be similar to what would be expected in a realistic situation where an infinite number of rays are used If a smaller number of rays are used there may be gaps along the great circle path where no rays reach the ground In order to build an oblique ionogram the receiver must receive energy from the transmitter But if a smaller number of rays are used it is possible that none of the propagated rays will EXACTLY reach the receiver Se
258. you to instantly determine what signal paths might cross into the influential auroral zones or what signal paths to use along the grayline etc The usefulness of this feature goes far beyond the simple establi shment of transmitter and receiver locations As you become more skilled in this use of this software you will discover the greater importance of these other included features You can save copies of these screen images to disk in one of several formats By pressing G you can save the screen to a GIF image file By pressing the P key you can save the screen image to a PostScript compatible file for sending to a laser pri nter And by pressing S you can save the screen image to a special format that can later b e used by PROPLAB to superimpose other information on For example you could superimpose contours of maximum usable frequencies on the map used to select transmitter and receiver locations The additional information included on these maps location of the au roral zones location of sporadic E the traced path between the transmitter and receiver gr ayline etc would provide a wealth of indispensable information when combined with contours of ionospheric properties See Section 4 for more information regarding these featu res 3 3 3 Ray Tracing Speed Path Type and Termination Mode When performing ray tracing functions in PROPLAB using the simple technique you can set the speed with which PROPLAB traces rays by using the t
259. ys If the traced rays begin to laterally deviate beyond the given lateral grid distance you will need to increase the distance of the lateral grid so that you can better observe where the traced rays propagate The lateral grid distance you specify is centered across the A line above For example by specifying a lateral grid distance of 500 kilometers the B line distance wil 1 be 500 kilometers spanning 250 kilometers on each side of the great circle A line 3 3 18 14 Distance between Ticks in Altitude This option defines how many ticks or lines should be used to define the altit ude wall of the three dimensional grid The default is 20 kilometers which provides reaso nably good resolution In other words a line would be drawn on the altitude wall every 20 kilometers in altitude The maximum height displayed on the altitude wall is determined by the HMax para meter given below 3 3 18 15 3 D Rotation Angles for the X Y and Z Axes This suboption defines how you want to view the three dimensional grid It lets you rotate the three dimensional grid in almost any conceivable fashion effectively changing the viewing perspective of the grid This gives you the ability to view traced rays at almost any angle desired The default rotation angles are 60 0 and 20 degrees for the X Y and Z axes respectively These rotation angles provide a good view of the traced rays both in altitude distance and lateral deviation 49 N

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