Computer Antenna Modeling Simplified – KE5KJD
Contents
1. f Xa I NANNY T ee XS St E ac A ww Evaluate Vertical Jumpers at Antenna Base to Resonate Vertical Four Jumpers Parallel One Jumper Bandwidth 493 Khz Bandwidth 512 Khz Speculation d Resonance Print BW 400 KHz Speculation All points BW 400 v ke SWR GainFB Fass 225 SWR 7 50 0 Bw 203 40 SWR lt 1 5 SWR Z 50 0 Bw 511 9 kHz SWR 2 0 SWR Min 7 09 Mhz Modeling My Colinear VHF Vertical Antenna designed by Speculation All points Detailed Resonance If Print mm Don Murray WOVE 2 or ME Setup SWR on Z 50 0 LN OE Ga 9 84 dBi 0 dB Vertical polarization F B 0 88 dB Rear Azim 120 dg Elev 60 dg Freq 146 000 MHz Z 30 349 j12 755 Ohm SWR 1 8 50 0 Ohm Elev 1 6 dg Real GND 10 00 m height Compare My Colinear With J Pole Reduces high angle radiation 10 49 dBi OdB Increased low angle gain Field s OV OH Total V H Modeling My Fat VHF Dipole Detailed Resonance Print Bw Bs SWR Gain FB Far fields Setup 15 Bw 20991 0 kHz SWR lt 1 5 i SWR on Z 50 0 Bw 6689 0 kHz SWR lt 2 0 i 12 PR Note slow SWR d Change Ga 6 06 dBi O dB Vertical polarization F B 0 00 dB Rear Azim 120 dg2. 18 Bw 618 2 kHz SWR 1 5 Bw 85460 8 kHz SWR lt 2 0 SWR on Z 50 0 27 Modeling My 2 Elernent Phased Vertical Weston 4 Band Vertical Reflector Director Butterut HF2V 80 40 Vertical Gutter downspout Hurricane Fence Hustler 6 Band Vertical 28 This is the current configuration of my verticals am attempting to use two of the multiband trap verticals as a two element system one fed antenna with the second used as a reflector Maximum gain improvement in the model shows about 3 DB gain So far have measured only 2 DB Also front to back in the model is much better than what observe Most of this is due to the lack of good measuring equipment and some is because my signal source is within the local near field zone of the antennas Using received signals as an indicator is also difficult because the signals vary much more than the improvement expect to see However extensive testing over time verifies the small 2 db improvement As a side note a full size 12 gauge copper wire inside a fiberglas fishing pole outperforms the trap vertical on 20 meters by about 1 2 db also have a saved model which includes my push up metal poles for the VHF antennas so that interactions between antenna systems can be estimated When originally locating the 2 Meter push up pole strong interactions were noted on 40 M because the pole was near resonant on 40 M The mod
3. Linear operator Unknown function Why Model Antennas To understand how antennas work To verify designs from literature To optimize a design for your particular needs frequency height application To create a new design To compare one antenna design against another To modify the resonant frequency of an existing antenna To understand the effects of a planned antenna modification To see the effects of varying the angle horizontal vertical of a dipole To determine the feedpoint impedance around the chosen frequency To place the antenna s at your location To see the antenna radiation pattern and take off angle To view induced currents in metal objects To avoid complex manual calculations For the pure joy of it Like working crossword puzzles Questions Answered By Modeling What is the radiation pattern for a given antenna at my location Will my roof gutters and clothesline poles affect the pattern What do need to do to the antenna to optimize it for my favorite portion of the band phone data cw How much of the band can use effectively with or without a tuner How much of a change can expect if increase the height from 25 feet to 45 feet aN gt a 6 What is the SWR curve over frequency look like at the antenna 7 What is the SWR curve look like at the transmitter end of my feedline 8 Can I place another antenna on the same support without deteriorating the performance 9
4. No segments 7 Copper c 58 MS m The basic part of antenna design is a wire or cylinder of appropriate dimensions with certain conductivity The element can be specified in segments or the program can perform segmentation for you Parts of the Antenna Model Excitation Sources Ideal voltage and current sources can be inserted in any segment Sources are used to excite a feedpoint Most antennas have a single feedpoint Aunit current source of 1 jO amperes generally works well Phased arrays with multiple antenna feedpoints can be driven with a separate current sources at each feedpoint or with a single source driving a feed network f a segment contains both source and load they are in series A voltage sources and load can be assigned to a segment when it is desired to simulate the Thevenin equivalent of a real generator needed for mutual impedance effects in phased array feeds A split feed consists of putting two half voltage sources in adjacent segments to simulates a source at the junction between the segments The source excitation for the antenna is usually placed at the feed point of the antenna It is also possible to feed the antenna at the end of a transmission line with given parameters Parts of the Antenna Model Wire Loads deal non radiating point loads can be inserted in any segment If a segment contains both source and load they are in series Loads are used to model coils
5. gt 9 R RN _ _ 2 t t The Butternut antenna has been in use by amateurs for a long time It has been touted as being able to operate with a minimal ground system which it does However the radiation efficiency varies greatly with the ground system In order to properly tune this antenna the large coils are squeezed or expanded until it resonates on both 80 M and 40 M In addition once resonated the match to 50 Ohm coax on 80 meters can be poor The standard solution is to put a coil across the feed point of the antenna See novel coil form above A good ground system will make this coil inductance value be fairly low This makes it a little more difficult to get the correct value The coil in this case will have few turns meaning that a fraction of a turn has more effect on the inductance value 16 Ground Screen Impedance Matcher This is the ground radials for the Hustler 6 band vertical At each grid junction each current will split Radial based on impedance ratios Superposition A ground screen has been placed over the ground radials On the right you can see how it functions to create a lowest impedance path to the ground rod can give you the theory for its operation amp but the real reason for the ground screen is to prevent me from adding ground wires There are approximately 120 wires of different types an
6. Elev 34 1 dg Real GND 12 20 m height G5RV A 1415 S Measured W5DXP Correction Measured 40 M SWR 4 WSDXP Dipole 4B 3ft Ladder 7 05 7 1 7 15 72 7 25 Frequency in Mhz Measured W5DXP Correction Measured 80 Meter SWR o 1 80 40 M Vertical 2 6BTV Vertical 3 ZS6BKW Dipole 4 WSDXP Dipole 4B 3ft Ladder Frequency in MHZ Measured W5DXP Correction Measured 20 M SWR 2 BTV Vertical 3f3 ZS6BKW Dipole 4 W5DXP Dipole 4B 3ft Ladder SWR 14 14 1 14 2 14 3 Frequency in MHZ Modeling My 2 Meter 6 Elernent Bearn 2 M Vertical Antenna Patterns Over 4 Mhz Frequency Range Speculation All points Detailed BW 4000 v KH Z SWR Gain FB Far fields Setup EE c s ss dcsssgx im ia Na ron mE t Colours 15 6 18 9 15 7 19 9 On 16 0 19 8 On 16 2 119 6 On 148 5 11 3 116 3 19 1 Field s OV OH 9 Total OV H Modeling 6 M 2 M 70 CM Antenna Well as you can guess the next step amp 3 is to see if they will all work on a common boom This version has the 2M 70CM elements in a vertical configuration which is appropriate for repeater contacts No significant interactions are observed with the three antennas ge eie X except for 70CM effects from the 2m piget que ake ce X 1
7. Elev 60 dg Freq 146 000 MHz Z 61 809 j7 503 Ohm SWR 1 3 50 0 Ohm Elev 3 8 dg Real GND 7 00 m height 2in OD Foil Over PVC Source Information And References http www fars k6ya org docs New Results on Antenna Impedance Models and Matching pdf http www wbddl org files Zs6bkw vs G5rv 20100221 files frame htm http www wbfc org files how to j pole J pole9o20slides ppt Compiled from the Internet for the AARA Ham Radio Club 2010 Computer Antenna Modeling Simplified KE5KJD An exposure to the benefits of computer modeling using software Archie asked me a few months ago if would be interested in presenting some information to the club about antenna modeling Not being an expert in the subject chose the topic Computer Antenna Modeling Simplified thinking that could present material that do understand and avoid any complicated questions on the subject This entire presentation is available on the AARA Club site at http www wb5ddl org This topic has become a high interest topic in the last 10 years because the computers available for personal use have the capacity and speed to perform the many calculations that at one time were done manually It is much easier to modify and test a computer model than a full sized antenna design especially at the HF and lower HF frequencies The typical PC of 1 GHZ and above has more processing power and memory than some of the supercomputers available only t
8. Where should place another antenna structure in my yard to minimize its effects or improve its effects 10 What SWR at 10 feet results in a given SWR at 40 feet 11 How much of my power is actually delivered to the antenna 12 What losses are introduced by the cable and other elements 13 Which antenna type should put up in my situation NOTE Modeling can save money time and shoe leather 1 2 3 4 5 6 7 8 How Software Modeling Works Define the geometry of the antenna Define the environment in which the antenna works Define the numerical evaluation parameters if different from a base set Select the center frequency for the initial antenna evaluation Select the lower and upper bounds for the plots View the results Make modifications then rerun until you are satisfied with results Sleep on it and start over the next day Most antenna modeling programs have extensive libraries of standard antenna designs to choose from so 1 above is not so bad Most have also tried to make the data entry as painless as possible but most fall short of easily referencing antenna elements and placement that the amateur radio operator would like KE5KJD adds his own elements to a basic library of antenna parts and uses these to build new designs Many have options to automate step 7 using supplied modification rules and some definition of success Parts of the Antenna Model Wires and Segments Each wire in an
9. antenna is defined by Location coordinates of both ends gt Diameter of wire Number of segments all equal in length Material or conductivity 0 9 90 9 9 9 9 o 2 X5 V2 2 Qi yp 2 Diameter AWG 12 Ya 22 No segments 7 Copper o 58 MS m Parts of the Antenna Model Excitation Sources Ideal voltage and current sources can be inserted in any segment Sources are used to excite a feedpoint Most antennas have a single feedpoint A unit current source of 1 jO amperes generally works well Phased arrays with multiple antenna feedpoints can be driven with a separate current sources at each feedpoint or with a single source driving a feed network If a segment contains both source and load they are in series A voltage sources and load can be assigned to a segment when it is desired to simulate the Thevenin equivalent of a real generator needed for mutual impedance effects in phased array feeds A split feed consists of putting two half voltage sources in adjacent segments to simulates a source at the junction between the segments Parts of the Antenna Model Wire Loads Ideal non radiating point loads can be inserted in any segment If a segment contains both source and load they are in series Loads are used to model coils traps and internally to NEC wire conductivity ohmic loss R L C Load types available are Ser
10. calculating radiation patterns My primary experience has been with the MMANA GAL version of MININEC primarily because it is pretty good at modeling and the price is right FREE have notices several recent antenna articles the use the program While NECA is the current favorite of professional designers its cost would most likely keep many hams from using it 10 MMANA Antenna Modeling Program Author Makoto Mako Mori JESHHT 1999 2000 Gontcharenko Gary DL2KQ EU1TT developed and released English versions of MMANA in 2001 2002 Nobuyuki Oba JA7UDE wrote an English user manual in 2001 Software beta testing was provided by a group of fellow amateurs Cost Freeware MMANA is an antenna analyzing tool based on the moment method introduced in MININEC Mini Numerical Electromagnetics Code Version 3 MININEC should not be confused with NEC which is a large antenna analysis program written in FORTRAN and designed to run on main frame computers A graphical user interface also was added that makes MMANA much easier to use than MININEC version it was ported from Some portions of later versions of MININEC are written in FORTRAN 11 MMANA GAL Prograrn Features Both table based and graphical based editors for antenna design and definition A3 dimensional graphical antenna viewer that shows antenna elements element current distributions and the elemental segmentations used Afar field radiation viewer that shows both
11. horizontal and vertical far field radiation patterns MMANA GAL 1 20 has 3 D far field display A comparator that can be used to compare two or more computation results Anantenna element editor Anantenna wire editor Tools for defining combinations of pipe or tube elements with stepped diameters Auser customizable automatic antenna optimizer capable of optimizing antenna designs with respect to jX SWR Gain F B Elevation and Current An antenna optimizer results display table with manual tuning capabilities Antenna frequency characteristics plotting An antenna specification file generator Plus many other things such as 3 dimensional antenna rotation antenna stacking and frequency scaling Many times simply copy the antenna definition file into a notepad text editor to make global changes which is quicker than modifying elements one by one also use this trick to insert pre defined ground planes metal objects and other antennas into the model without manually entering them each time then just update the wire count to match 12 MMANA MMANA GAL Differences keen nee SAA rain cat aa eel ToT DoW 7 Geometry View Calculer ar 31d p ole 8 72 dBi 0dB Hori Pol 0 00 d8 Rear Az 120 dg E1 80dg Freq 14 150 MHz 2 60 SWR 1 83 60 0 11 98 6000m Elev 23 9dg Real GND 16 0mH 1 MMANA v 1 77 Both of these pro
12. the modeling It is still barely usable on this band but certainly not optimal 21 Modeling My 2 Meter 6 Element Beam 22 This antenna is mounted on a TV push up pole with a TV rotator It lets me easily get into Baton Rouge and Abbeville repeaters It is evolving into a mulltiband 2M 440 and 6M antenna as seen in the models to follow The boom is a 1 x 2 wood beam with spar varnish left over from a previous project The elements are straightened copper tubing cut from a 50 ft roll of refrigerator tubing which is lighter and less expensive than solid wire Aluminum tubes would work nearly as well 22 2 M Vertical Antenna Patterns Over 4 Mhz Frequency Range Speculation All points Detailed Resonance Print BW 4000 KH 72 SWR Gain FB Far fields Setup Colours _ F B ON 18 9 On 19 9 On 19 8 On 19 6 On 19 1 On Field s OV OH Total OV H The directional properties on 2 meters are excellent The front to back ratio is also very good This design saved me about 150 over a commercial version Tests conducted with W5JXC indicated both good gain and front to back ratio with this antenna 23 Modeling 6 M 2 M 70 CM Antenna Well as you can guess the next step is to see if they will all work on a common boom This version has the 2M 70CM elements in a vertical configuration which is appropriate for repeater contacts No significant in
13. 1 88 dBi 0 dB Horizontal polarization F B 16 82 dB Rear Azim 120 dg Elev 60 dg Freq 50 500 MHz Z 46 634 j1 058 Ohm seg Shown to the left is the pattern Of the Moxon with all elements In place Not too bad Antenna SWR on 6 Meters Speculation All points Detailed Bw 2000 KHz SWR Gain FB Far fields Setup Bw 1715 0 kHz SWR 1 5 SWR on 2 50 0 Bw 3116 1 kHz SWR 2 0 Antenna SWR on 2 Meters Plots Speculation All points Detailed BW 2 SWR Gain FB Far fields Setup 14 Bw 8670 1 kHz SWR lt 1 5 SWR on Z 50 0 Bw 20558 1 kHz SWR 2 0 Antenna SWR on 70 CM Plots Speculation All points Detailed BY 10000 SWR Gain FB Far fields Setup 1 8 r Bw 618 2 kHz SWR lt 1 5 SWR on Z 50 0 Bw 85460 8 kHz SWR lt 2 0 Modeling My 2 Element Phased Vertical Weston 4 Band Vertical Reflector Director Butternut HF2V uti 80 40 Vertical Gutter and downspout Hurricane Fence Hustler 6 Band Vertical Vertical Beam Antenna Pattern on 20 Meters kure O ai e pfi NN PIN NY T 11 4 WY Mi Vertical Beam Antenna Pattern on 40 Meters pem ALPE N OH THREE n Cd PRA TRA SS BS IA NRR IH
14. Club design It works just as expected and that matches the results of modeling About 2 5 db gain over a quarter wave or J pole design The antenna is mounted on top of a metal TV type push up pole also have that modeled with the other antennas so that interactions can be observed on the HF bands 33 Compare My Colinear With J Pole Reduces high angle radiation ND Increased low angle gain Field s EY p F Load mab file Clear Colour Return 34 This shows another useful feature of MMANA GAL where you can compare one antenna pattern against another This one gives you a sense of why the colinear is a good choice for a base antenna It goes almost twice as far on transmit or receive This is not obvious from looking at the antenna pattern by itself 34 Modeling My Fat VHF Dipole x Note slow S ram Change 14 1440 125 5 146 0 1470 128 5 i 420 P 2 in OD Foil Over PVC This will be the antenna to bring to special events Itis not bothered much by close objects or people and has a very stable SWR to match a hand held or mobile transmitter Howerer the design is not much better than the Arrow antenna or any other half wave VHF antenna 35 Source Information And References http www fars k6ya org docs New Results on Antenna Impedance Models and Matching pdf http www w5ddl org files Zs6bkw vs Gbrv 20100221 file
15. Compiled from the Internet for the AARA Ham Radio Club 2010 Cornputer Antenna Modeling Simplified KE5KJD An exposure to the benefits of computer modeling using software Antenna Modeling What is it Computerized antenna modeling is evaluating the performance of a system that is governed by the laws of physics Antenna modeling programs are computer programs that use mathematics to calculate and predict the electrical performance of an antenna Modeling usually has its limitations partly because the mathematical model that we have to describe it can almost never be described in the same detail as the real thing and especially its environment and partly because of numerical limitations in the calculating code used or imposed by the developer The final limitation is the operator who enters the data and who interprets the results In all cases a good deal of knowledge and experience in the field of antennas is required in order to draw the correct conclusions and take the right decisions during the process of modeling However almost anyone with a computer and data entry skills can select an antenna design of a given type and change it to match their constraints and view the results Start With Simple Equations Pocklington s equation 1897 1 2 Lc See 8 joe E p a 1 2 Hallen s equation 1938 1 2 AN Ez yz ETB oy Cs 2 l TP General form ALL r g Driving function
16. ch their constraints and view the results Most computer modeling programs in use today use rather simple calculations on segments of radiators and accumulate its effects on every other segment and in free space This method is commonly called the Method of Moments Another method uses the differential equations and calculate answers using a Finite Difference calculation to arrive at the answer No matter which method extreme care must be taken in the numerical calculation using as much precision as required to get accurate results Also the number of segments used depends on the closeness of elements and complexity of the element connections amp Start With Simple Equations amp Pocklington s equation 1897 1 2 29 1 e 5 k penk jo E p a 2 OZ Hallen s equation 1938 jkR 1 2 2 az B sink z D EC 4zR Hu General form AFLP g 4 Driving function Linear operator Unknown function Aren t we all glad that we do not need to get into the intricacies of these equations to model our antennas The numerical programmers however need to understand these equations and also the best way to represent them numerically Why Model Antennas To understand how antennas work To verify designs from literature To optimize a design for your particular needs frequency height application To create a new design To compare one antenna design against anoth
17. d lengths making up the radial system If did not put the screen would most likely still be adding ground radials to the system Enough is enough Adding the ground screen was like putting a period at the end of a sentence 17 Modeling My ZS6BKW And W5DXP 40 20 17 12 10 6 Pattern b SWR Height Effects Band Tradeoffs 80 40 Optimum Feed Length Interactions Best orientation Ground Effects Distortion due to Metal Objects 0 Antenna Gain Crossed Dipoles Fed with Measured Length of Ladder line Then 50 Ohm Coax Coax PON Ook aN 20 Meter SWR Curves Radiation Pattern ZS6BKW 20M 20 Meter 3D Radiation Pattern ZS6BKW Radiation Pattern Relative to Antenna This antenna configuration is my bread and butter antennas for HF work The ZS6BKW model is extensively covered in the evaluation vs ZS6BKW which is presented in its entirity on the AARA club web site http Awww w5ddl org files Zs6bkw_vs_G5rv_20100221_files frame htm can hardly wait until can get it up to a decent height because the model shows it will perform better at 45 feet than at 30 feet However even at the reduced height can run the ZS6BKW on 5 bands using the internal tuner on my transceiver also enjoy less loss with this antenna than with multiple fan dipoles or trap dipoles Currently my 6 band vertical will outperform this antenna on most far DX contacts primarily because of its excellent radial s
18. e an English user manual in 2001 Software beta testing was provided by a group of fellow amateurs Cost Freeware MMANA is an antenna analyzing tool based on the moment method introduced in MININEC Mini Numerical Electromagnetics Code Version 3 MININEC should not be confused with NEC which is a large antenna analysis program written in FORTRAN and designed to run on main frame computers A graphical user interface also was added that makes MMANA much easier to use than MININEC version it was ported from Some portions of later versions of MININEC are written in FORTRAN MMANA GAL Program Features Both table based and graphical based editors for antenna design and definition A 3 dimensional graphical antenna viewer that shows antenna elements element current distributions and the elemental segmentations used A far field radiation viewer that shows both horizontal and vertical far field radiation patterns MMANA GAL 1 20 has 3 D far field display A comparator that can be used to compare two or more computation results An antenna element editor An antenna wire editor Tools for defining combinations of pipe or tube elements with stepped diameters A user customizable automatic antenna optimizer capable of optimizing antenna designs with respect to jX SWR Gain F B Elevation and Current An antenna optimizer results display table with manual tuning capabilities Antenna frequency characteristics plotting An antenna specificati
19. e antenna length shortened by 5 meters and elongated by 5 meters The same was done by changing the ladder line length by 5 meters shorter and longer recording the new resonant frequency each time This sensitivity number can be then computed in cycles changed in megahertz per inch 19 Measured W5DXP Correction Measured 80 Meter SWR 6 5 5 54 Original 4 5 W5DXP e 1 80 40 M Vertical 4 s 2 6BTV Vertical 3 5 Corrected 4 3 ZS6BKW Dipole 3 W5DXP 4 W5DXP Dipole 4B 3ft Ladder 2 5 1 5 1 T T 3 5 3 6 37 3 8 3 9 4 Frequency in MHZ This graph shows the change in resonant frequency on 80 meters which is better within the DX window may in the future decrease the antenna length and increase the ladder line length to move the resonant frequency to about 3 92 MHZ on 80 M because check in to NET frequencies in this range For the time being will leave it as it is 20 Measured W5DXP Correction Measured 20 M SWR 6 Original 1 80 40 M Vertical x Corrected s8 2 6BTV Vertical W5DXP j 3 ZS6BKW Dipole 4 4 WSDXP Dipole X x x A 4 3ft Ladder 3 m yg X 2 1d 14 14 1 14 2 14 3 Frequency in MHZ 21 This graph shows the change on 20 M which indicates that the change made things worse on this band as expected from
20. el indicated that needed to move the 2 M pole about 40 feet to minimize the interaction This was before pouring the concrete footing for the mast 28 Vertical Beam Antenna Pattern on 20 Meters 29 H e hti CX 29 Vertical Beam Antenna Pattern on 40 Meters 30 30 Vertical Beam Antenna Pattern on 80 Meters Phased Feed i 31 NOTE on this band the antennas are too close together to get good directional gain and front to back gain differentials A dual phased feed is required to get the above pattern Without modeling it would have taken many measurements to determine that it would not work without phasing the two elements So will have to find another way determined BEFORE attempting to build the antenna 31 Evaluate Vertical Jumpers at Antenna Base to Resonate Vertical Four Jumpers Parallel Bandwidth 493 Khz Bandwidth 512 Khz SWR Min 7 09 Mhz The question came up on the design as to whether the antenna system could be tuned using switched jumpers to ground The above model was constructed which indicated that it would work on 40 Meters In addition if the jumpers were paralleled then as the number of jumpers was increased we also got a small bonus in increased bandwidth because of the thicker wire cage at the bottom of the antenna The antenna was changed for 20 Meters and the results were similar with
21. er To modify the resonant frequency of an existing antenna To understand the effects of a planned antenna modification To see the effects of varying the angle horizontal vertical of a dipole To determine the feedpoint impedance around the chosen frequency To place the antenna s at your location To see the antenna radiation pattern and take off angle To view induced currents in metal objects To avoid complex manual calculations For the pure joy of it Like working crossword puzzles Antenna modeling is not at all fun unless you get results that satisfy your requirements It does however make one aware of all that needs to be specified and known about our antenna before we can view results that we can use and trust in putting together our own antenna Many times in modeling antennas was made aware of why my implementation of someone s design did not perform as well as the author s version mostly due to my lower height of the antenna It also explained why some antennas like the colinear W5YI on 20 meters is such a good high gain antenna even at low antenna heights Questions Answered By Modeling What is the radiation pattern for a given antenna at my location Will my roof gutters and clothesline poles affect the pattern What do need to do to the antenna to optimize it for my favorite portion of the band phone data cw How much of the band can use effectively with or without a tuner How much of a cha
22. grams are free Both give good results on most antenna designs The MMANA GAL v 1 2 0 20 does have a 3D visualization mode which can be an advantage when looking at obstructions and their effects on the radiation fields 13 Modeling Roof Effects on G5RV Zack Roof and Antenna i Model Antenna Pattern Zack was concerned about his G5RV and the possible interaction with his metal roof A model of the roof was added to the G5rv model and run It showed some interaction mostly good because the metal roof had stronger reflections than the lossy ground and gave some additional gain in the direction opposite the roof 14 Modeling My HF2V Butternut Ea mecs pie ee 40M 80 40 Vertical Detail Of m Matching EN _ Coils This was a somewhat difficult antenna to model because of the interaction of the two large resonating coils It is also somewhat difficult to tune in real life for the same reason needed this to work because 1 needed to know what value of coil to put across the feed point to lower the SWR on 80 meters without severe negative effects on 40 meters It took fewer turns than most of the suggestions in the literature but very close to the model results 15 Modeling My Real HF2V Butternut Radial System 1 Capacitor AW ANOS He Vey Matching Coil u E xc lt
23. ies Constant impedance jx gt Series RLC network a gt Parallel RLC network Trap network Parallel RLC Laplace impedance positive real rational function R g L up to 5th degree Trap P jo a joy a Cjo a jo a jo a jo a eat Y Q jo b jo b joy b jo b Which Program Do Use NEC Numeric Electromagnetics Code NEC 2 Public Domain Single diameter wires 4NEC2 Free version of NEC 2 EZNEC Pro W7EL Active ham developer Sales NEC 4 Latest version from Lawrence Livemore Labs 250 License MMANA GAL EZNEC with spreadsheet antenna definition GAL ANA MININEC 3 and NEC2 calculations Demo version only in active development QUO GI B I The MININEC versions are adequate for most applications NEC 4 models most situations including an accurate ground system MMANA GAL does not have accurate results near ground but does include variable element diameters and tapered elements NEC 4 has the most up to date features and is used by antenna design professionals You should look up these programs on the internet if you need additional information KE5KJD uses MMANA GAL because it is free and does reasonable job of calculating radiation patterns MMANA Antenna Modeling Program Author Makoto Mako Mori JESHHT 1999 2000 Gontcharenko Gary DL2KQ EU1TT developed and released English versions of MMANA in 2001 2002 Nobuyuki Oba JA7UDE wrot
24. ion All points Detailed Resonance Print BW 200 2 SWR Gain FB Far fields Setup 210 SWR on Z 50 0 Radials Modeling My Real HF2V Butternut Radial Bypass Capacitor UN 2 80 Coil e a A a Ls nm w Pus ij _ y 1 Matching Coil d EE Ground Screen Impedance Matcher This is the ground radials for the Hustler 6 band vertical At each grid junction each current will split Radial based on impedance ratios Superposition Modeling My ZS6BKW And W5DXP 40 20 17 12 10 6 gt 1 Pattern Te 2 SWR 3 Height Effects 4 Band Tradeoffs 80 40 9 Optimum Feed Length 6 Interactions Crossed Dipoles 7 Best orientation me d Fed with Measured 8 Ground Effects Length of Ladder line 9 Distortion due to Metal Objects 50 10 Antenna Gain 20 Meter SWR Curves Radiation Pattern ZS6BKW 20M 20 Meter 3D Radiation Pattern ZS6BKW SWR on Z 500 S Radiation Pattern 20 Meters 14 MHz Relative to Antenna 34 750 14 6 Deg Orientation Gain 2 DBi Eme oisi eram Note 6 Deg pattern is same antenna at lower 6 degrees takeoff angle Ga 8 51 dBi 0 dB Horizontal polarization F B 0 01 dB Rear 120 dg Elev 60 dg T Freq 14 175 MHz Z 62 588 j3 567 Ohm My ZS6BKW SWR 1 3 50 0 Ohm 29 5 ft
25. nge can expect if increase the height from 25 feet to 45 feet What is the SWR curve over frequency look like at the antenna What is the SWR curve look like at the transmitter end of my feedline Can place another antenna on the same support without deteriorating the performance 9 Where should place another antenna structure in my yard to minimize its effects or improve its effects 10 What SWR at 10 feet results in a given SWR at 40 feet 11 How much of my power is actually delivered to the antenna 12 What losses are introduced by the cable and other elements 13 Which antenna type should put up in my situation out orm ouo NOTE Modeling can save money time and shoe leather The questions listed are some of the many reasons we may want to model an antenna BEFORE making changes or putting it up in the air In addition to the reasons listed the model can be used to verify observed results especially when we do not expect the changes we are observing How Software Modeling Works 1 Define the geometry of the antenna 2 Define the environment in which the antenna works 3 Define the numerical evaluation parameters if different from a base set 4 Select the center frequency for the initial antenna evaluation 5 Select the lower and upper bounds for the plots 6 View the results 7 Make modifications then rerun until you are satisfied with results 8 Sleep on it and start over the next day Most a
26. ntenna modeling programs have extensive libraries of standard antenna designs to choose from so 1 above is not so bad Most have also tried to make the data entry as painless as possible but most fall short of easily referencing antenna elements and placement that the amateur radio operator would like KE5KJD adds his own elements to a basic library of antenna parts and uses these to build new designs Many have options to automate step 7 using supplied modification rules and some definition of success Making a software model primarily involves inputting the definition of our antenna elements Some programs are better than others at accepting inputs or making changes to portions of the antenna None have used are as easy as think they should be want to build my element with variable lengths etc and keep them in a library of my chosing that can reference easily into my design Like a trap vertical that can then use on a boom as a dipole or Yagi Some of the designs have worked with required many many iterations to come up with the final design so ease in modification is a real plus Parts of the Antenna Model Wires and Segments Each wire in an antenna is defined by gt Location coordinates of both ends gt Diameter of wire gt Number of segments all equal in length gt Material or conductivity 09 9 9 9 9 9 9 9 AX A Z 2 21 Diameter AWG 12 0 Ya 22
27. o research and government groups in the past This presentation will show that modeling is one way to try out antenna designs before building and testing them It doesn t take long to convince yourself that building antennas with software is more accurate less time consuming and a heck of lot safer and cheaper than the real thing However one must remember the objective to have an real antenna system that will allow you to enjoy the hobby on an ongoing basis Antenna Modeling What is it Computerized antenna modeling is evaluating the performance of a system that is governed by the laws of physics Antenna modeling programs are computer programs that use mathematics to calculate and predict the electrical performance of an antenna Modeling usually has its limitations partly because the mathematical model that we have to describe it can almost never be described in the same detail as the real thing and especially its environment and partly because of numerical limitations in the calculating code used or imposed by the developer The final limitation is the operator who enters the data and who interprets the results In all cases a good deal of knowledge and experience in the field of antennas is required in order to draw the correct conclusions and take the right decisions during the process of modeling However almost anyone with a computer and data entry skills can select an antenna design of a given type and change it to mat
28. on file generator Plus many other things such as 3 dimensional antenna rotation antenna stacking and frequency scaling MMANA MMANA GAL Differences amp 2 MMANA GAL C MyCrypt HamRadio Antennas MMANA GAL ANT HF multibands Only size GR5V_ZSBKW_VeeDip 19 ox MMANA E MyCrypt HamRadio Antennas MMANA GAL ANTIHF multibands Only size GR5V_ZSBK File EHit Service Tools Help File JEdit Options Help 02 var Geometry View Compute Far Field Plot For eld piots GRbV ANTENNA ZS6BKW VEE 7 90 dg 62 872 dBi 0 dB Horizontal polarization k Ga 8 72 dBi OdB Hori Pol 0 00 dB Rear Azim 120 dg Elev 60 dg A i Freq 14 150 MHz THU F B 0 00 dB Rear Az 120 dg El 60dg E Freq 14 150 MHz Elev 23 9 dg Real GND 16 00 m height 2 50 2944j30 794 SWR 1 83 50 0 11 96 6000m Elev 23 9dg Real GND 16 0mH Elevation x Ovh Elevation a CH Total V H MMANA GAL v 1 2 0 20 MMANA v 1 77 3 D viewer only in V 1 2 0 20 Modeling Roof Effects on GSRV Zack Roof and Antenna Antenna Pattern V Modeling My HF2V Butternut Speculation All points Detaile Resonance Print BW 300 Z SWR Gain FB Far fields Setup 3 0 w 97 2 kHz SWR 1 5 182 5 kHz SWR 2 0 80 40 M Vertical Detail Of Matching Coils Speculat
29. s frame htm http www wbfc org files how to j pole J pole9620slides ppt 36 Sources will be added as time permits 36 Click to add title Click to add an outline 37
30. shorter jumpers required It also led to a scheme of tuning the antenna to the higher end of its range for the short jumper case and to the low end of the band using the longer jumper and simply connecting more or less variable length jumpers in parallel for the tuning The plan is to use 7 relays Cat 5 control Cable and a bank of binary switches to parallel the jumpers from the shack This will allow tuning the vertical with 128 different combinations of wires Not all will be useful The lowest frequency jumper may need to be a coil if the antenna is to be used on 80 meters not likely The parallel combinations will allow tuning on multiple bands 10 M 40 M Testing of this arrangement was done in two ways One was to receive steady signals on the band while inserting and removing the jumpers on the reflector The second way was to transmit through the antenna system exciting the driven element and looking at the signal on a field strength meter It was much easier to measure the attenuation on the back side of the antenna because the F B ratio of the antenna is much higher 8 10db than the forward gain difference 2db 32 Modeling My Colinear VHF Vertical Rescnance Prnt Bw Antenna designed by Don Murray W9VE z SWR sanrB Farfelcs Setup 22 SWR denn 1452 1460 47 0 1480 This is the first antenna I built after getting my Technician license based a Dallas Texas
31. teractions are observed with the three antennas s except for 70CM effects from the 2m 4 antenna c4 A X Ga 11 88 dBi 0 dB He rizontel polarization F B 16 82 dB Rear Azim 120 dg Elev 60 dg Su t GoD Shown to the left is the pattern E P E cH Of the Moxon with all elements In place Not too bad This will be the finished antenna all turned by the same TV rotator Right now am unsure whether can run them all with the same coax feed because the model indicates touchy resonance when all fed from the same coax However with careful modeling have a 50 ohm feed point impedance on 2 Meters not the 22 ohms in many conventional designs 24 Antenna SWR on 6 Meters atio All points etaile BW 2000 2 SWR Gain FB Far fields Setup 3 0 Bw 1715 0 kHz SWR lt 1 5 Bw 3116 1 kHz SWR 2 0 The SWR will be adjusted on the final assembly Right now these graphs indicate that should be able to get a reasonable match to 50 Ohms 25 Speculation All points Antenna SWR on 2 Meters Detailed 2 SWR Gain FB Far fields Setup Resonance Print BW 4000 M 14 Bw 8670 1 kHz SWR 1 5 Bw 20558 1 kHz SWR lt 2 0 SWR on Z 50 0 26 Speculation All points Antenna SWR on 70 CM Detailed E SWR Gain FB Far fields Setup Resonance Print BW 10000 v
32. traps and internally to NEC wire conductivity ohmic loss Load types available are vx v v v v Constant impedance jx Series RLC network Parallel RLC network Trap network Laplace impedance positive real rational function up to 5th degree R L Series RLC L R Parallel RLC Trap _ P jo a joy a jo a joy a joy a jo a Z f Q jo b JO b jo b joy b joy b jo b Loads can be used at any point within an element to represent inductive loading resistive losses or traps Which Program Do Use NEC Numeric Electromagnetics Code NEC 2 Public Domain Single diameter wires 4 2 Free version of NEC 2 EZNEC EZNEC Pro W7EL Active ham developer Sales NEC 4 Latest version from Lawrence Livemore Labs 250 License MMANA GAL EZNEC with spreadsheet antenna definition GAL ANA MININEC 3 and NEC2 calculations Demo version only in active development DUO co mw The MININEC versions are adequate for most applications NEC 4 models most situations including an accurate ground system MMANA GAL does not have accurate results near ground but does include variable element diameters and tapered elements NEC 4 has the most up to date features and is used by antenna design professionals You should look up these programs on the internet if you need additional information KE5KJD uses MMANA GAL because it is free and does a reasonable job of
33. ystem On local and US contacts the ZS6BKW dipole will most often outperform the vertical The W5DXP which is a 148 foot long dipole with a tuned 450 ohm ladder line feeder is resonant on BOTH 80 and 40 meters providing an alternative antenna for the two low bands where the ZS6BKW is a little weak 18 Measured W5DXP Correction Measured 40 M SWR Original W5DXP 1 80 40 M Vertical 2 6 Vertical 3 ZS6BKW Dipole H4 WSDXP Dipole Corrected x 4 3ft Ladder SWR T T 7 7 05 71 7 15 7 2 7 25 73 Frequency in Mhz This graph shows actual SWR measurements of all my antenna HF systems The W5DXP antenna as measured when first put up had a resonance too high on this band The computed sensitivity to a change in ladder line length and antenna length from the model indicated that a longer ladder line would improve the SWR on 40 meters and also on 80 meters The ladder length was changed by about 32 inches to obtain the improvement shown as predicted by the model It also showed that the antenna length would need changing to maintain the resonance on 80 meters Since wanted a slight decrease in resonant frequency on 80 M to get closer to the DX window at 3 79 Mhz opted to only change the ladder length by How was the sensitivity determined Simply recording the resonant frequency of the antenna at the nominal measurement and with th
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