Xnec2c User Manual
Contents
1. On the top row of widgets this window has the same Viewer angle selection buttons and spin button displays as the Main window The two buttons at the middle right Gain and E H select either the Gain or the Near Electric Magnetic Field pattern display Provided there are at least two steps in the theta and one in the phi angle as specified in the Radiation Pattern RP command the Gain pattern will be calculated and drawn The E H field will be properly drawn if there are at least two points specified in the NE or NH commands The Frequency Loop control buttons at the far right can be used to Start Pause and Reset the loop The View menu in addition to the Common Projection and Common Frequency check buttons provides sub menus for selecting Polarization type Gain Scaling and the Near Field data to be drawn The selection of polarization type affects the Gain pattern the displayed Viewer gain and the value of max and min gain as shown to the left and right of the color code bar The selection of gain scaling only affects the form of the Gain pattern drawing Linear Power is the most realistic since the distance from the origin of each point in the gain pattern is proportional to the radiated power density as is the color code red for max gain and magenta for min gain A disadvantage of this scaling is the inadequate representation of side lobes since they are usually significantly weaker than the main beam Linear Voltage is better in thi2. option where n is the number of processors in a SMP machine xnec2c will 06 21 2014 09 00 PM Xnec2c User Manual http www gqsl net 5b4az pkg nec2 xnec2c spawn n child processes to which it will delegate calculation of frequency dependent data for each frequency step Thus data related to n frequency steps will be calculated concurrently and passed on the the parent process by pipes to be further processed for graphical display Child processes are spawned before GTK is initialized and started so that only the parent process is tied to the GUI interface Thus there are n 1 processes running when the j option is used and execution is faster by slightly less than n times Please note that its pointless and counter productive to specify a value of n greater than the number of steps in the frequency loop Built in NEC2 input file editor Xnec2c has a built in editor for NEC2 input files Data in NEC2 cards can be entered or edited either directly in the main editor window tree view or in more convenient dedicated editors for each type of card Edited data can be saved to a NEC2 input file and reloaded for execution so that the edit execute display cycle is quicker and more convenient 3 Limitations Since xnec2c is interactive it cannot operate in the same way as NEC2 or nec2c Specifically commands that cause execution in NEC2 nec2c XQ RP etc are only read in but not acted upon unless the user requests the display of relev
3. 9b Fixed a few bugs mainly in the NEC2 editor code and also changed the code of all individual Geometry and Command editors so that edited data are set in the main NEC2 editor s tree views when another Geometry or Command card tree view row is selected for editing Implemented a work round around a serious bug which I could not trace since it now seems to be outside my code When the zint or foar functions are called they seem to corrupt xnec2c s memory allocation when they return This corruption manifests itself as NAN values appearing in calculations so modified these functions to return their computed value via a pointer in the argument list also changed the function declaration from complex long double to void as it seems this bug is related to functions of the former type declaration returning a value Version 1 0b In this version xnec2c has been re worked extensively to make it multi threading and to streamline its operation to some extend Many bugs created by these changes and others that already existed have been fixed and the user interface has also changed somewhat The example input files have also been checked and some mistakes in them have been corrected This is now the first version 1 0 beta release for public testing Version 1 0b3 Added setlocale LC_NUMERIC C to the main function so that in locales where commas are used in decimal numbers xnec2c can read data correctly suggested by Joop Stakenborg Som
4. The Radiation Pattern menu item opens the Radiation Pattern window so that the Gain pattern or the Near E H fields can be calculated and displayed The Frequency Data item opens the Frequency Data Plots window which allows the plotting of various frequency related data against the frequency range specified in the FR command It also allows quick selection of the current frequency and recalculation of data by clicking on the plots drawing area The Polarization sub menu allows the selection of different polarizations for which many data items are calculated e g gain F B ratio etc The selection is global e g it effects all relevant data that are drawn or displayed in other windows The Common Projection item couples the projection viewing angle parameters of the Structure display in the Main window and the Gain or E H field display in the Radiation pattern window so that both move in step Similarly the Common Frequency menu item couples the Frequency entry display spin buttons in the same windows so that displayed data are for the same frequency The Radiation Pattern window E Xnec2c Radiation Patterns Emm File View c i att E H Fields Frequency Loop Step 21 1 M 4 2502 1 20 dB 0 980 MHz Apply 7 Radiation Pattern Total Gain Linear Power View Radiation x y z el 2 45 BR a5 Zoom 100 G a 6 of 18 06 21 2014 09 00 PM Xnec2c User Manual http www gqsl net 5b4az pkg nec2 xnec2c
5. The default is 1 0 Hz Clicking the Apply button starts an animation of the near fields using the specified parameters The OK button does like wise but it closes the animation dialog while Cancel stops the animation The Total Field sub menu allows the selection of drawing either the Peak value or a time frozen Snapshot of the instantaneous value of the total Near Field E H vectors The Snapshot values are calculated as the vector sum of the X Y Z components of the E H field and the Peak values are calculated using the formula NEC4 uses to print the Peak field values 7 of 18 06 21 2014 09 00 PM Xnec2c User Manual http www gqsl net 5b4az pkg nec2 xnec2c The Overlay Structure menu item enables the drawing of the structure in the radiation pattern drawing area when the Near Field pattern is selected for drawing This makes it easier to understand the scale and extend of the Near Field patterns around the structure The color scheme for the structure becomes white when Overlay is enabled unless it is overridden by either the Current or Charge distribution being enabled by the relevant buttons in the Main window In the second row of widgets the Color Code bar shows either the max and min values of Gain in the radiation pattern or the maximum value of the field strength in the near E H field pattern Of course only one value can be shown the precedence being E field H field or Poynting field strength depending on which of these is
6. are read in but not acted upon Any data in the lines of these commands are saved for use when the user requests output data calculation and display via buttons and menu items in the GUI Also since xnec2c was designed to visualize output data 13 of 18 06 21 2014 09 00 PM Xnec2c User Manual http www qsl net 5b4az pkg nec2 xnec2c graphically certain types of output data requests are not supported e g the surface wave pattern option 11 1 of the RP command etc An error message dialog will hopefully appear to inform the user of unsupported commands or options Here is a list of Commands or command options not supported by xnec2c GF Read Numerical Green s Function Relevant code has been removed in nec2c since this type of solution is obsolete WG Write Numerical Green s Function Relevant code has been removed in nec2c since this type of solution is obsolete NX Next Structure Data Relevant code has been removed since xnec2c cannot operate in batch mode PQ PT CP These commands affect printed output and have no effect on data presented by xnec2c in graphical form Since version 1 0 xnec2c does not print results to file SOMNEC The separate SOMNEC code has been incorporated in nec2c and hence in xnec2c also EX When Incident Wave or Elementary Current Source Excitation is specified xnec2c can only calculate and render the re radiated field produced by the current induced onto the structure Only the initial values of t
7. enabled in the View gt Near Field sub menu The Text Entry widget at the right of the color bar shows gain in the direction of the viewer perpendicular to screen while the Frequency Spin button following it shows the current frequency in MHz for which data is displayed It can also be used to enter a new frequency in the same manner as in the Main window The Redo Check box enables re calculation and display of data when the frequency value changes while the button to its right causes same when clicked by the user but only if a new frequency has been entered Currently the Gain pattern is drawn as a transparent wire frame with each line segment colored according to the average value of gain associated with the two points it joins The pattern can be dragged with the mouse pointer to rotate or tilt it and it can also be positioned using either the X Y Z or Default right arrow buttons The Rotate and Incline spin buttons can also be used to accurately position the Gain pattern in the window The label in the drawing area s frame gives information on what is on display and also the type of polarization or gain scaling Starting with version 2 1 the radiation pattern display can be zoomed in or out by using the mouse wheel or the Zoom controls Zoom spin wheel and the 1 buttons and it can also be moved around by dragging with the right mouse button 2 Both the Gain and Near Field patterns can be saved as PNG image files by using the
8. in the EX card Although this is not supported in xnec2c it still produces a segmentation fault because the ipnt buffer is not allocated in the netwk function in network c Version 1 2 Made the page size of spin buttons 0 to make setting of spin button values compatible with GTK 2 4 Version 1 3 After an inquiry about using incident field excitation which was not implemented in previous versions removed the restrictions in excitation to allow plotting the re radiated pattern from a structure excited by incident field or elementary current source However the calculations are carried out only for one set of angle of incidence angles e g there is no stepping of the theta and phi angles This would require much more complex changes to xnec2c and am not currently able to do this Version 1 4 Applied a patch supplied by Tom Beierlein DL1JBE to fix crashing of xnec2c 1 3 on long input file names gt 80 characters Version 1 5 Changed the handling of command line arguments so that the input file name may be specified without the use of the i option In this case xnec2c will take the last argument to be the input file name but only if it has the nec extension Got rid of some variables that were set but not used according to warnings given by gcc Applied a patch supplied by Rik van Riel to allow the calculation of front to back ratios when the antenna is modeled over ground Version 1 6 received another bug report from Ri
9. input impedance is such that a 16 1 quadrifilar toroid CM transformer should raise it to 50 Ohms zi 4 Edit Geometry Data Wire Arc Helix Patch Cylinder Move Reflect Scale Geometry ene lia E E E leo lea a 10 of 18 06 21 2014 09 00 PM Xnec2c User Manual http www qsl net 5b4az pkg nec2 xnec2c 3 0 00000E 00 0 00000E 00 1 32000E 01 5 99500E 0 1 5 99500E 00 0 00000E 00 1 32000E 01 5 53800E 0 16 0 00000E 00 0 00000E 00 0 00000E 00 0 00000E 00 1 1 00000E 00 0 00000E 00 1 30000E 01 0 00000E 0 m Edit Control Commands Excitation Frequency Ground GN Loading Network Trans Line Radiation Near Fields Ground GD Kernel Interaction Execute Commands 0 00000E 00 0 00000E 00 0 00000E 00 9 80000E 01 2 00000E 03 0 00000E 00 1 00000E 00 0 00000E 00 0 00000E 00 3 70000E 07 0 00000E 00 0 00000E 00 gt Xnec2c has a built in NEC2 input file editor to make the edit save execute cycle easier and quicker The main editor window opens from either the File gt New or File gt Edit menu items of the Main window The File gt New menu item opens the editor with some default rows cards that amount to a free space vertical dipole which serves as a simple example The File gt Edit menu is used to edit a NEC2 input file that is already open in xnec2c The main NEC2 input file editor can be used to directly edit rows if desired and indeed this is the only
10. spawn by forking so that the total number of processes running will be n 1 n should be equal to the number of processors in a SMP machine Please note that its pointless and counter productive to specify a value of n greater than the number of steps in the frequency loop h Print usage information and exit v Print version information and exit The Main Window B Xnec2c Structure Display SIGE File View Help Currents Charges Frequency Loop Step 21 B 3 193E 01 1 20 dB 1 000 2 MHz Apply View Currents X Y Z el a5 a 45 Zoom 100 al a E 5 S lt By 2 5 G y 4 of 18 06 21 2014 09 00 PM Xnec2c User Manual http www qsl net 5b4az pkg nec2 xnec2c When starting xnec2c from a terminal or from a file manager by OLE the i option can be used to specify a NEC2 input file xnec2c i nec2 turnstile nec Otherwise an input file can be opened from the Main window s File gt Open menu item If the input file is valid xnec2c will render the structure specified in the Geometry section of the file in the Main window s drawing area The background color is black and the structure is rendered in blue The excitation points segments are rendered in red the x y z axis in white loaded segments in yellow transmission lines in cyan and two port networks in magenta These colors are hard coded in the source code and at this stage of development there is no option to change them
11. the drawing area with button 3 right button sets the frequency to the nearest frequency loop step value as marked by the little boxes or diamonds on the graphs However all the displayed frequency related data are still recalculated and refreshed e g buffered values are not used Clicking with button 2 middle button cancels the green frequency marking line 9 of 18 06 21 2014 09 00 PM Xnec2c User Manual http www gqsl net 5b4az pkg nec2 xnec2c The top row of widgets in this window has at its right buttons to select data to be plotted against frequency These are Max Gain Maximum gain and front to back ratio at each frequency step Dir The direction of maximum gain e g the radiation angle relative to the xy plane 90 theta and the phi angle as defined in NEC2 Viewer The gain in the viewer s direction e g perpendicular to the screen VSWR Zo The VSWR for the Zo value in the Impedance Spin button default 50 Ohm Zr Zi The real and imaginary parts of the input impedance Zm Zph The scalar magnitude and phase of the input impedance The View gt Net Gain menu item changes the second plotted quantity to the Net Gain of the array This was added after a feature request for xnec2c The Frequency Loop control buttons at the top right can be use to Start Pause or Reset the loop As the loop progresses more data will be presented in the graphs and in the text entry widgets above the graph drawing area These widgets dis
12. this the Frequency Spin Button shows the current frequency in MHz for which the current charge distribution and Viewer gain are calculated and displayed If the Redo Check box is active each time the frequency is changed in the spin button all relevant data on display will be recalculated If not clicking the Redo button will initiate recalculation Printing of results to an output file has been removed starting from version 1 0 since xnec2c works in a way that does not allow printing compatible with the NEC2 format If printing to file is needed then it is better to use the original NEC2 program to avoid bugs that may still be lurking in the C translation Otherwise it is possible to save the structure drawing to a PNG file by using the Save or Save As items in the File menu Starting with version 2 1 xnec2c can save the structure display as a data file for the gnuplot plotting program This is done by using the File gt Save As gnuplot menu item to open a file chooser dialog If only the stem of the file name is given xnec2c will automatically add the gplot extension Plotting in gnuplot is done with the splot 5 of 18 06 21 2014 09 00 PM Xnec2c User Manual http www qsl net 5b4az pkg nec2 xnec2c lt filename gt with lines command although the plot can be enhanced with some of the style etc commands available in gnuplot The View menu allows opening of other output data display windows and selection of various options
13. wire diameter to be specified but then convert this to radius when entering to the Main editor and saving to file NEC2 requires wire radius to be specified Three geometry Editors wire helix arc have a spin button to specify wire conductivity in Siemens meter When the spin button value is greater than zero the Editor will enter an LD card in the Commands tree view to specify a type 5 wire conductivity loading This will result in all segments with tag number equal to that in 12 of 18 06 21 2014 09 00 PM Xnec2c User Manual http www qsl net 5b4az pkg nec2 xnec2c the Editor to be loaded with the specified resistivity Please note that Deleting the GW row in the Geometry tree view will not remove the LD loading row in the Commands tree view All editors except for the GE card have the following buttons along the bottom of the window New inserts a new blank row in the tree view after entering edited data into the current row Delete Card removes the current row card and closes the editor window Apply enters edited data into the current row OK enters edited data into the current row and closes the editor window Please note that the GE row is entered automatically by the first editor used if the tree view is cleared and there is no button for it in the Geometry frame But there is a dedicated editor for it which opens with a right click on the selected GE row and it should be used to specify the presence of Groun
14. 0 0 995 1 000 1 005 1 010 1 015 1 020 Frequency Data Plots window is the main display of frequency related data such as maximum gain VSWR input impedance etc Most data can be plotted against frequency and some are displayed in text entry widgets It is also a convenient way to quickly enter a new current frequency by clicking on the graph drawing area The following applies to all graphs plotted in this window When a graph of two quantities against frequency is plotted e g real and imaginary parts of input impedance then one quantity is plotted in magenta color and its scale is at the left vertical side of the bounding box The second quantity is plotted in cyan color and its scale is at the right side while a short descriptive title is printed in yellow at the top horizontal side The graph bounding box is in white and the scale grid lines are in light gray When only a single quantity is plotted against frequency it is plotted in magenta color and the scale is at the left side of the bounding box Once graph plotting is complete e g the frequency loop is done clicking on the graph drawing area with button 1 left mouse button will produce a vertical green line in the graph bounding box marking the new current frequency and triggering a re calculation of all frequency related data Also displays and drawings in all open windows assuming the Redo check boxes are ticked active will be refreshed to present the new data Clicking on
15. File gt Save or File gt Save As menu items The Save option will save the drawings with a suitable default file name which includes a serial number so that consecutive Saves do not overwrite files but please note that when xnec2c is restarted the serial numbers are reset so that overwriting will occur if the same input file is opened Starting with version 2 1 xnec2c can save the radiation pattern and near E H field display as a data file for the gnuplot plotting program This is done by using the File gt Save As gnuplot menu item to open a file chooser dialog If only the stem of the filename is given xnec2c will automatically add the gplot extension Plotting in gnuplot is done with the splot lt filename gt with lines command although the plot can be enhanced with some of the style etc commands available in gnuplot jia Data Plots window The Xnec2c Frequency Data Plots Bmx File View Max Gain Direct Viewer vswe 2r Zi Zmi Zph Freq Loop E F MHz 1 000 Max Gain 4 255 VSWR 1 067 Zrealj 3 128 Zimj0 154 Zo 3 0 Frequency Data Plots Total Gain 8 of 18 06 21 2014 09 00 PM Xnec2c User Manual http www gqsl net 5b4az pkg nec2 xnec2c 0 980 0 985 0 990 0 995 1 000 1 005 1 010 1 015 1 020 10 00 VSWR VSWR vs Frequency 0 00 L_ a ee Pe a 0 980 0 985 0 990 0 995 1 000 1 005 1 010 1 015 1 020 3 500 Z real Impedance vs Frequency 3 400 3 300 3 200 3 100 3 000 2 900 0 980 0 985 0 99
16. LDTYP 5 when wire conductivity S m was specified in the GW card Wire editor The same bug was present in the GH Helix card editor and it was also fixed added code so that the wire conductivity for GW GA and GH cards can be read from the relevant LD card and shown in the Conductivity S m spin button After all these changes checked the xnec2c source code using the Coverity Scan service and fixed an out of bounds read error that was reported by the scanner in the plot_freqdat c file Version 2 8 Fixed a bug in the GN card editor function which caused xnec2c to save the GN card parameters in the nec antenna description file without clearing the number of radials to zero This resulted in the GN card editor window to open with confusing and incorrect defaults for the radial screen when the Reflection Coefficient Approximation method was selected for specifying ground parameters 17 of 18 06 21 2014 09 00 PM Xnec2c User Manual http www qsl net 5b4az pkg nec2 xnec2c Also fixed some bugs missing variable initializations in the Ground Parameters calculation functions which resulted in incorrect Radiation Pattern calculations This would happen if a nec file with Perfect Ground iperf 1 specified in the GN card was opened after a nec file with a Radial Ground Screen specified in the GN card was processed Version 2 9 After a request by the Debian maintainer of xnec2c added a rudimentary man page he sent me and
17. Once an input file is opened the structure display can be rotated around the Z axis and tilted about a horizontal axis through the origin This can be done either by pressing button 1 and dragging the structure with the mouse pointer clicking the X Y Z or the right arrow Default view button 45 deg rotation and tilt The actual value of rotation and tilt is shown in two spin button widgets which can also be used to change the viewing angle Starting with version 2 1 the structure display can be zoomed in or out by using the mouse wheel or the Zoom controls Zoom spin wheel and the 1 buttons and it can also be moved around by dragging with the right mouse button 2 The current distribution or charge density in the structure can be displayed by clicking the Cur or Chg toggle buttons at the top right of the Main window The distribution of current or charges is rendered by a color code red for the maximum value and magenta for zero The Frequency Loop control buttons can be used to Start Pause or Reset the loop There is a Color Code bar at the left of the second row of widgets in the Main window indicating the color coding and the maximum value of the displayed quantity at its right The title in the border of the drawing area widget shows the user selected function of the display while the text entry widget at the right of the color code bar shows antenna gain in the Viewer direction e g perpendicular to the Screen To the right of
18. Xnec2c User Manual http www qsl net 5b4az pkg nec2 xnec2c Xnec2c User Manual Xnec2c is a GTK2 based Graphical version of nec2c the C translation of NEC2 1 Introduction 2 Features o Interactive Operation o No Output File o Windows o Color Codin o On demand Calculation o Multi threaded operation on SMP machines o Built in NEC2 input file editor Limitations Compilation and Installation Operation o Command Line Options o The Main Window o The Radiation Pattern Window o Frequency Data Plots o NEC2 Input File Editor Input File Considerations Output File Considerations Version History Bugs and Inadequacies Acknowledgment 1 Introduction U BW OO ONO 1 Xnec2c is a GTK2 based Graphical version of nec2c my translation to the C language of NEC2 the FORTRAN Numerical Electromagnetics Code commonly used for antenna simulation and analysis The original nec2c is a non interactive command line application that reads standard NEC2 input files and produces an output file with data requested by commands in the input file In contrast xnec2c is a GUI interactive application that in its current form reads NEC2 input files but presents output data in graphical form e g as wire frame drawings of the radiation pattern or near E H field graphs of maximum gain input impedance vswr etc against frequency and simple rendering of the antenna structure including color code representation of currents or cha
19. ant data For example if an RP command line is included in the input file xnec2c reads the relevant data from that line but does not calculate render the radiation pattern until the user requests this by opening the Radiation Pattern window and clicking on the Gain button In addition the NX and WG GF commands are not recognized since only one structure at a time can be input and evaluated and the Numerical Green s function is not needed or implemented Also some options of certain commands e g the surface wave option 1 1 of the RP command are not implemented and they must not be used since they will disrupt or even crash xnec2c There are advantages deriving from the interactive operation it is possible for example to specify both the NE and NH commands in combination with a multiple frequency FR card although only the relevant data of the last command will be used 4 Compilation and Installation Please note that use Void Linux AMD64 which is a bleeding edge type distribution so there may be compilation and or run time difficulties if you are using a relatively old distro This is mostly true of the basic dependencies like GTK 2 and Glade 2 and there can also be sound card incompatibility problems at run time To compile the package it may be preferable to first run the included autogen sh script in the package s top directory to produce a fresh build environment Then the configure script can be run with optional param
20. corrected some spelling errors arbitary to arbitrary 9 Bugs and Inadequacies Xnec2c is based on nec2c my translation to C of the original FORTRAN NEC2 code Any bugs discovered in nec2c will affect xnec2c as well and they will have to be fixed In addition changing the flow logic of nec2c from a non interactive batch processing command line tool to a GUl based interactive application was rather complex and introduced many bugs that were fixed but it is always possible that a combination of some input file with an untested sequence of user actions may trigger a hidden bug Such a case in fact did appear and it was traced to a bug in the original NEC2 code This has been fixed by G Burke and the fix has been incorporated in nec2c and xnec2c See the NEC2 bug txt file for details When xnec2c was made multi threading a lot of bugs appeared and were fixed but again there may be some that have not showed up One condition that did appear a couple of times was xnec2c getting blocked in a select call waiting for a child to write to a pipe This apparently happened because was testing a very minimal input file and the child processes seemed to write to the pipes before the parent process dropped into select If this seems to happen do not enable multi threading don t use the j option for very simple jobs A known inadequacy of xnec2c is the slowness of the animation of displayed drawings e g the structure itself the radiation patte
21. d GN command etc Sample Dedicated Control Editor G6 Excitation Command EX Card om Excitation Type Voltage Source O Incident Linear Wave O Incident RH Wave O Incident LH Wave Current Source O Current Slope Discontinuity Print Control O Maximum Admittance Matrix Asymmetry L Impedance of Source Segment Excitation Parameters Tag Number Segment Number 7 pI Voltage Real Part Voltage Imaginary Part Normalization Factor 1 00000 B 0 00000 B 0 00000 2 NOT USED NOT USED NOT USED 0 00000 B 0 00000 a 0 00000 2 New amp Delete Card f Apply 0K Excitation Command Editor The Excitation Command Editor opens when the Excitation button in the Edit Control Commands frame is clicked or when a selected EX row is right clicked with the mouse The excitation type is selected by activating the appropriate radio button whereby some labels over the data input spin buttons will change to indicate their purpose The print control check buttons specify additional data to be printed to the output file but please remember that xnec2c does not produce an output file The buttons in the bottom row of the Command Editors function in the same way as the Wire editor described above 6 Input File Considerations Since xnec2c is interactive it will not initiate calculations without a prompt from the user For this reason certain NEC2 commands that normally cause execution e g RP XQ etc
22. d system to be compatible with the current version of these tools at the time of writing February 2013 Version 2 3 beta Fixed a bug in the cell_edited_callback function that caused segmentation fault crashes when a cell in the input file editor was edited directly by the user Version 2 4 submitted xnec2c and nec2c for scanning to the Coverity source code audit website which produced a list of no less than 57 issues to be fixed Most of them were not bugs that affected calculations but possibly two both in the Somnec code one in function rom1 and one in gshank likely could have caused errors in the relevant calculations Unfortunately the Fortran source of Somnec as well as that of the NEC2 is very difficult to read so cannot say with certainty if this was SO Version 2 5 After a bug report by Jean Collin made some changes to the input file parser code in input c to properly identify tabs in the input file Version 2 6 After a bug report by Lucjan SQ9VPA changed the case of the signal handler that deals with SIGCHLD so that it doesn t cause xnec2c to exit when the SIGCHLD signal does not originate from child processes created by xnec2c It appears that in some Linux installations a SIGCHLD signal is sent to xnec2c even if it is not running forked e g the j option is not used in the command line Version 2 7 After a bug report by Tim WJ5Q fixed a bug that was preventing the creation of an LD card of type 5
23. e minor changes to the user interface were also made to allow the NEC2 editor window to fit in displays with shorter heights Version 1 0b4 After a bug report from Juha Vierinen changed some sprintf commands to snprintf to avoid buffer overruns Version 1 0b5 Following on the above changes revised all similar situations in xnec2c s source and modified all sprintf commands to snprintf just in case as could not replicate the bug so could not test for other similar problems also fixed a bug in the save and save as handler to avoid false attempts by xnec2c to save structure and radiation pattern frequency plots pixmaps when a save of the NEC2 editor data failed for some reason Version 1 0 After several months with no bug reports or feature requests am sticking my neck out and releasing xnec2c as version 1 0 This version incorporates the last two feature request received from users The Cancel button on card editors has been replaces with a Delete Card button which deletes the selected card row in the NEC2 editor window A Net Gain menu item has been added to the View menu of the Frequency Plots 15 of 18 06 21 2014 09 00 PM Xnec2c User Manual http www qsl net 5b4az pkg nec2 xnec2c window to replace the second plotted quantity with the Net Gain of the antenna Version 1 1 spoke too soon A segfault bug has been reported that occurs when Maximum Admittance Matrix Asymmetry printing is requested
24. ec2c to reload the edited input file for execution Note In xnec2c versions earlier than version 2 0 beta due to the complex file opening process followed by NEC2 many data sanity checks and initializations etc 11 of 18 06 21 2014 09 00 PM Xnec2c User Manual http www qsl net 5b4az pkg nec2 xnec2c reloading the input file resulted in all open windows radiation pattern frequency plots to be closed This was always an awkward situation and slowed down work in the NEC2 input file editor As of xnec2c version 2 0 beta the user interface as well as a fair amount of code in xnec2c have been modified so that as far as possible when an edited NEC2 file is saved and reloaded or another NEC2 file is opened xnec2c will not close open Radiation Pattern or Frequency Plot windows and will not completely reset internally This allows the user to edit a NEC2 file in the Editor window and after saving to be presented with the new calculations on the structure being modeled Finally the Revert button reloads the last saved state of the editor from the input file to reduce the effort needed to recover from a big mistake like clearing a tree view accidentally Sample Dedicated Geometry Editor Description Wire Il Wire Element GW amp GC cards Ses Geometry Editor This O Tapered Wire is one of the Tag Number No Segments Segs lambda Wire Diameter dedicated 1 18 2 00827 0 00600 card or
25. ency related Data like Input Impedance VSWR Max gain F B Ratio Gain in the Viewer s direction etc Both the Main window and the Radiation Pattern window have buttons to select fixed viewing angles of the structure or the radiation pattern as well as spin buttons to input specific viewing angles Color Coding Xnec2c uses color coding to visualize the Current or Charge distribution in the Structure s segments or patches as well as the Gain pattern or the Near E H field pattern Color coding is also used to clarify the Graphs of Frequency related data A color code strip is shown in the Main and Radiation Pattern windows On demand Calculation Since xnec2c collects data to be displayed in buffers directly from the functions that produce them there is no need to produce and parse an output file and no need to re run the program when certain input data currently the frequency is changed or when different output data gain near fields input impedance etc is required The frequency can be changed either from spin buttons in the Main and Radiation Pattern windows or by clicking on the Frequency Data window s graph drawing area The frequency corresponding to the pointer position will then be used to re calculate whatever data is on display Multi threading operation on SMP machines Since version 1 0 xnec2c can run multi threaded by forking on SMP machines when executing a frequency loop Multi threading is enabled by using the j lt n gt
26. equivalent Cairo graphics equivalents e g replaced gdk_draw_line with cairo_line_to since Cairo provides for nicer anti aliased drawing After a feature request by David J Singer and friend Richard have added code to save data of the structure display radiation patterns and frequency plots into file in 16 of 18 06 21 2014 09 00 PM Xnec2c User Manual http www qsl net 5b4az pkg nec2 xnec2c a format suitable for the gnuplot plotting program Version 2 1 Patched a problem in the graph plotting routines that caused xnec2c to crash with a division by zero fault This can happen when e g a single wire structure is specified and a plot of gain vs frequency is requested for a polarization that is at 90 deg to the wire e g requesting gain plot for horizontal polarization for a vertical wire Since there is no radiation in the horizontal plane of a vertical wire the values of gain given to the plotting routines are all the same so the vertical scale drawing routines crash xnec2c Please note that although xnec2c will now not crash as above the plots will be jumbled and meaningless Version 2 2 beta made extensive modifications to the source code to silence a large number of warnings generated by the LLVM clang compiler when used with the Weverything option These were mostly cases of implicit conversions between variable types like int to char or uint to int etc have also updated the basic files of the GNU Autotools buil
27. eters to override the default settings and compiler flags e g configure prefix usr CFLAGS g O2 will override the default usr local installation prefix and the Wall O2 compiler flags Running make in the package s top directory should produce the executable binary in src Running make install will install the binary into usr local bin by default or under the specified prefix It will also install the default configuration file into the user s home directory This will have to be edited by the user as required There is also this hypertext documentation file which you can copy to a location of your choice No configuration files are needed and the sample input files that were used during development are in the xnec2c examples directory Please also read the xnec2c doc 3 of 18 06 21 2014 09 00 PM Xnec2c User Manual http www qsl net 5b4az pkg nec2 xnec2c nec2c txt file that describes the nec2c application that is used as the basis for xnec2c 5 Operation Command Line Options Xnec2c has the following command line options i lt input file name gt Specify a NEC2 input file to be opened at start up If the i option is omitted xnec2c will take the last argument to be the input file path name but will only open it if it has the nec extension j lt number of child processes to spawn gt Since version 1 0 xnec2c can run multi threaded on SMP machines This option specifies the number of child processes to
28. he theta and phi angles are used and no stepping of these angles is performed Therefore it is better to specify only one step for theta and phi in the EX card RP The surface wave option 11 1 is not supported 7 Output File Considerations Printing of results to an output file has been removed starting from version 1 0 since xnec2c works in a way that does not allow printing compatible with the NEC2 format If printing to file is needed then it is better to use the original NEC2 program to avoid bugs that may still be lurking in the C translation 8 Version History Version 0 1 First version with ability to draw a color coded wire frame Radiation Pattern Near and Far Field Graphs of various Frequency dependent data Gain VSWR Impedance etc and the Structure Wires Patches including a color coded Current or Charge distribution Version 0 2 Incorporated some changes to the GUI the Glade generated design since after upgrading to GTK 2 8 9 the geometry of the windows the position and extend of buttons entry widgets changed a little Also fixed some bugs in the GUI code to handle unusual sequences of user actions correctly Version 0 3 Added the ability to stop the frequency loop by clicking on the frequency display spin buttons and to restart it by toggling the Gain or E H buttons in the Radiation Pattern window Version 0 4b Added a NEC2 input file editor that makes the edit save reload execute cycle easier and q
29. k van Riel The patch applied above did not help as somehow the buggy code got duplicated below the bug fix reproducing the same error in the calculation of front to back ratio Hopefully fixed this time Version 2 0 beta received a bug report from David Binderman regarding an array bounds violation which he found by compiling xnec2c with the D_FORTIFY_SOURCE gcc flag fixed this bug and also tested xnec2c source code using cppcheck decided it was about time modify the xnec2c user interface so that it will as far as possible allow the user to save and re open NEC2 files in the Editor window without closing the Radiation Pattern and or the Frequency Plots windows This will significantly soeed up work on editing NEC2 files and also make xnec2c usage less awkward However many bugs were introduced and fixed during this re write of xnec2c so users are advised to be watchful of possible bugs that got away and to report them for fixing Version 2 1 beta have introduced many changes in this version so am releasing it again as a public beta version for testing and bug reports After a bug report by David J Singer changed all declarations of variables that are used in memory allocations from int to size_t This error was in the nec2c code from the beginning but apparently it only showed up when extremely large memory allocations are requested in nec2c and xnec2c have replaced all the deprecated GDK drawing primitives with
30. method available for editing Comments The editor though has several dedicated sub editors for each of the type of card that is indicated in the Buttons above the Geometry and Commands Tree Views The dedicated editor windows open when these buttons are clicked to add a new row or when a selected row is right clicked by the user with the mouse Main Editor Description The Main NEC2 Editor window is divided into three Tree View areas one for editing Comments one for editing Geometry and one for Control Commands Each tree view has editable rows divided into cells that correspond to NEC2 input file s card columns e g Card Name CM Comment Text or Card Name GW Wire Data 11 12 F1 F2 F3 F4 F5 F6 F7 etc Each row can be edited by selecting it with a mouse click and then clicking on a cell This requires detailed knowledge of the format of each of the NEC2 input file cards and so this method is only useful for editing comments The main editor is controlled by the top row of buttons The Add button inserts a new blank row in whatever tree view has been selected by a mouse click The Remove button deletes a row that was selected by a mouse click and the Clear button deletes all rows in a selected tree view and clears it The Save As button opens a file selector dialog for saving the data in the Editor to a NEC2 input file The Save button writes data in the Editor to an already open input file The Apply check button when checked signals xn
31. play the current frequency in MHz the maximum gain in the radiation pattern for that frequency the VSWR for the Zo value in the spin button above and the real and imaginary parts of the input impedance The File gt Save and File gt Save As menu items can be used to save the graphs in the drawing area as PNG image files with a default file name or one of the user s choice respectively The View gt Polarization sub menu can be used to select the wave polarization type for which data is calculated and presented When Viewer gain plotting is enabled the graph will be re drawn when the structure projection is changed by the various means described earlier dragging by mouse pointer Rotate Incline spin buttons etc Starting with version 2 1 xnec2c can save the frequency dependent functions as a data file for the gnuplot plotting program This is done by using the File gt Save As gnuplot menu item to open a file chooser dialog If only the stem of the filename is given xnec2c will automatically add the gplot extension Plotting in gnuplot is done with the plot lt filename gt with lines command although the plot can be enhanced with some of the style etc commands available in gnuplot NEC2 Input File Editor GE Xnec2c NEC2 Input File Editor HHn Edit Tree View Rows NEC2 Input File df Ada Remove Clear Save As F Save lt Apply Revert Comments CM Top loaded helical vertical for 1 0 MHz over perfect ground CM The
32. rge densities These results are only calculated and drawn on user demand via menu items or buttons e g xnec2c is interactive and does not execute NEC2 commands in batch style as the original does Printing of results to an output file has been removed starting from version 1 0 since xnec2c works in a way that does not allow printing compatible with the NEC2 format If printing to file is needed then it is better to use the original NEC2 program to avoid bugs that may still be lurking in the C translation Xnec2c now has a built in editor for NEC2 input files which can be used to edit geometry or command card data This basic editor displays comment geometry and command cards in tree views where individual rows each representing a card can have their cells edited directly for raw entry of data More useful are pop up editor windows that open when appropriate buttons are clicked or when a selected row is right clicked with the mouse These editors allow easier more convenient entry 1 of 18 06 21 2014 09 00 PM Xnec2c User Manual http www qsl net 5b4az pkg nec2 xnec2c and editing of individual rows with no need for detailed knowledge of card formats When editing is completed the contents of the nec2 editor can be saved ina NEC2 compatible input file which can then be re loaded by xnec2c for execution 2 Features 2 of 18 Interactive Operation Xnec2c is interactive in its operation e g when started it just shows i
33. rn near fields pattern etc Specifically dragging these drawings with the mouse to rotate or incline them seems very heavy on processor loading and with most structures the movement is jerky This is my first attempt at animated wire frame drawings and lack experience with GTK2 in this field so probably went about this the wrong way am open to any suggestions that may solve this problem 10 Acknowledgment Some of the code in xnec2c is based on Pieter Tjerk de Boer s xnecview application which visualizes NEC2 s input and output files The general look and feel of xnec2c was also influenced by the same application Author Neoklis Kyriazis Ham Radio call 5B4AZ September 20 2005 18 of 18 06 21 2014 09 00 PM
34. row editors for Wire X1 Wire Y1 Wire Z1 Wire Length creating or 2 40000 2 o 00000 2 90000 3 61248 editing wire geometry It Wire X2 Wire Y2 Wire Z2 Conductivity S m will appear 0 00000 0 00000 fo 20000 0 00000 when the Wire button in the Edit T Delete Card lt Apply 0K Geometry Data frame is clicked or when a selected Wire row is right clicked with the mouse In the former case a blank GW row will be added to the Geometry tree view which can then be filled by entering wire geometry data in the Editor and clicking Apply or OK in the latter case the editor is closed The Tapered Wire check button in the upper left corner opens an additional frame for entering wire taper data and adds a blank GC row to the tree view To make things easier the Wire editor has spin buttons to specify Length Taper and Diameter Taper separately to hide the need for calculating the actual beginning and end diameters Also the Segs lambda spin button indicates the wire segment length as a percentage of smallest wavelength and can be use to set the needed number of segments for each wire to maintain a uniform relative segment length for all wires Please note that this function will only work if the Frequency FR card is specified in the Commands tree view and all the data is saved to file and read by xnec2c so that frequency data is valid in xnec2c s buffers Please also note that all dedicated editors require
35. s respect since the position of points in the gain pattern is proportional to Electric field strength and hence follows a square root law ARRL Style follows a form of logarithmic scaling suggested by the American Radio Relay League e g exp 0 058267 gain where gain is in dB10 Finally Logarithmic follows a logarithmic scale with a median of 40dB When a Near Field NE or NH command is included in the input file clicking the E H button produces a drawing of the near Electric and or Magnetic fields By selecting the Near Field gt Poynting Vector menu item the Poynting vector is also drawn These fields are depicted by lines of fixed length in the direction of the relevant E H Poynting vector at each point in the drawing The field strength is depicted by the color of the lines as using the line length for this purpose makes most lines too small to be useful The drawing of the Near E or H Fields can be enabled or disabled by the Near Field gt Near E Field and Near Field gt Near H Field menu items The Near Field gt Animate Dialog menu item opens a dialog box for setting the parameters and starting an Animation of the near field pattern The Steps Cycle spin button allows the setting of the number of angular steps around a cycle of the excitation input The default is 36 and it results in angular steps of 10 degrees The Animate Frequency spin button specifies a fictitious slowed down excitation frequency for which the animation is performed
36. ts Main window ina blank state indicating that no valid input data has been read in yet The NEC2 type input file can be specified at start up in the command line optionally with the i option or it can be opened from the file selection dialog that appears via the File gt Open menu of the Main window Once a valid input file is opened all the normal widgets in the Main window appear so as to allow proper operation The NEC2 commands in the input file are read in but not executed until a request is issued by the user via buttons or menus in the appropriate windows No Output File Printing of results to an output file has been removed starting from version 1 0 since xnec2c works in a way that does not allow printing compatible with the NEC2 format If printing to file is needed then it is better to use the original NEC2 program to avoid bugs that may still be lurking in the C translation Windows In its current form xnec2c has three windows for the graphical display of output data When started without an input file specified optionally by the i lt input file gt option the Main window opens with most of the button and menu widgets hidden When a valid input file is opened all the hidden widgets are shown and the structure is drawn in the Main window s drawing area widget From the View menu the Radiation Pattern and Frequency Related data display windows can be opened to draw either the Gain pattern or the Near E H fields or Frequ
37. uicker Version 0 5b Fixed a bug that caused segmentation faults when only one wire segment was present in the structure This is not a case that will normally exist but the seg fault had to be fixed Version 0 6b Fixed a bug inherited from NEC2 If no geometry cards are present only a GE card then there is division by zero in conect NEC2 seems to accept the lack of geometry cards this is now an error condition in xnec2c Reduced the max value specification of the Capacitance spin button in the Loading card editor from 14 of 18 06 21 2014 09 00 PM Xnec2c User Manual http www qsl net 5b4az pkg nec2 xnec2c 1 0e 12 to 1 0e 9 pF since the higher value is beyond the range of the long type in 32 bit systems Modified the behavior of some card Editors to make them more user friendly Version 0 7b Fixed a bug in the co ordinate translation Move editor and edited the code in the GW card editor so that the wire diameter does not change when the New button is clicked Version 0 8b Fixed a serious bug that caused segmentation faults and crashes in structures that have a wire in contact with a patch The subph routine divides this patch into 3 or 4 sub patches so the total number of patches increases There was no provision to reallocate and initialize buffers used in rendering patches in the structure display window Other minor bugs were also fixed and the example NEC2 files were also checked and edited when needed Version 0
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