[antennaware] NEC2 Visualization

Kenneth Earl Harker kharker@cs.utexas.edu
Sun, 3 May 1998 23:24:21 -0500 (CDT)

     I am working on a term project in my visualization (computer graphics)
class this semester involving the visualization of certain aspects of the 
radiation pattern of antennas modeled with NEC2.


     At the moment, we have created a small application with a main window
in which the graphics happen and a few buttons and slider bars and whatnot 
below it.  The program loads in a .nec file from disk, draws the antenna
in the main window from the data in the GW cards, and puts in boom, antenna
mast and groundplane objects in the case of a yagi (I haven't tried this with 
other types of antennas just yet.)  Currently, we can visualize the 
antenna's gain pattern as well as its polarization sense pattern, and we're
aiming to visualize numerous other aspects of the antenn radiation field
as well.

    In all the images on our web page, the color green indicates that NEC2
reported a LINEAR polarization sense at that point in the pattern.  White
indicates RIGHT sense and blue indicates LEFT.  I find it very interesting
that the pattern is symmetric, but the polarization sense pattern looks very 

    Now, to my questions; I'm not especially knowledgable about antenna
modelling, having learned most of what I know for this particular
project.  Given output like what I'm attaching below, what would you
like to see graphically visualized?  Gain, of course, we're already doing,
and polarization sense is probably easy.  Would visualizing POLARIZATION
TILT be useful?  PHASE DEGREES maybe?  Any other ideas? 

                                                - - - RADIATION PATTERNS - - -

  - - ANGLES - -           - POWER GAINS -       - - - POLARIZATION - - -    - - - E(THETA) - - -    - - - E(PHI) - - -
 DEGREES  DEGREES       DB      DB      DB        RATIO     DEG.              VOLTS/M    DEGREES      VOLTS/M    DEGREES
   90.00      .00    -999.99   18.86   18.86     .00000   -90.00  LINEAR    0.00000E+00      .00    7.20823E+00    98.52

   Also, is there an easy way to determine in a .nec input file where the 
electrical center of the antenna is?  RP output data is given in polar 
coordinates, presumably centered at the lectrical center of the antenna,
and I'm interested in knowing where the appropriate place to locate the center
of our rendered pattern; presently we're putting it at the physical center,
which is easy to determine.

    Finally, the application we're working on is currently only running on 
Silicon Graphics IRIX boxes; it should be possible to recompile it without 
modification for Linux and other UNIX boxes, and in principle there's no 
reason we couldn't get it run on a Windows box eventually (I think - my 
knowledge of Windows is marginal at best.)  

     I'm interested in any feedback/suggestions/comments.


Kenneth E. Harker      "Vox Clamantis in Deserto"      kharker@cs.utexas.edu
University of Texas at Austin                  Amateur Radio Callsign: KM5FA
Department of the Computer Sciences         President, UT Amateur Radio Club
Taylor Hall TAY 2.124               Maintainer of the Linux Laptop Home Page
Austin, TX 78712-1188 USA            http://www.cs.utexas.edu/users/kharker/

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