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Re: [dxatlas] HamCap and ITS HF antennas

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  • Alex, VE3NEA
    Hi Steve, HamCap is designed to work with antenna model types 13 and 14 that are just tabulated antenna patterns, 2-D and 1-D respectively, vs. frequency. The
    Message 1 of 1 , Mar 19, 2004
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      Hi Steve,

      HamCap is designed to work with antenna model types 13 and 14 that are just
      tabulated antenna patterns, 2-D and 1-D respectively, vs. frequency. The
      program may work with other file types as well, but you will not be able to
      view the antenna patterns. To add a new antenna file, drop it in the
      HamCap\AntBkup\ folder and restart the program.

      It is fairly easy to create your own files of types 13 and 14.

      Type 14 is a table of antenna gain vs. the elevation angle and frequency.
      Use it for omni-directional antennas, like verticals, and for directional
      rotated antennas. In the latter case, we are not interested in the
      horizontal pattern because we always point the antenna at the dx, so only
      the vertical pattern of the main lobe matters.

      Type 13 is a huge table of antenna gain vs. azimuth, elevation, and
      frequency. Use it only for fixed directional antennas.


      I used the 4nec2 freeware antenna modeling program to create a 13-type model
      of my sloper. The program is available at ftp://ftp.qsl.net/pub/wb6tpu/NEC/
      .

      The description of another modeling program, MultiNEC
      (http://www.qsl.net/ac6la/), is very promising, but I have not tried it
      myself.


      There is another way of creating type 13 and 14 antenna files that does not
      require 3-rd party programs. It is based on the fact that VOACAP generates
      antenna pattern tables on the fly from other file types when it calculates
      its predictions. In the following example we will create a model of your 3/2
      wl vertical.

      1. Start the HFANT program that comes with VOACAP, select File -> New
      Type -> ITSA-1 IONCAP -> Type 22: Vertical Monopole in the menu, set the
      antenna parameters, and save the file as 3_2_GP.ANT. The file will look like
      this:

      ----------------------------------------------------------------------------
      ----
      3/2 wl Ground Plane
      7 7 parameters
      0.00 [ 1] Max Gain dBi
      22 [ 2] Antenna Type
      14 [ 3] Ground Dielectric Constant (1-80)
      0.00600 [ 4] Ground Conductivity (.00003-5.0 mhos/m)
      10.000 [ 5] Operating Freq
      -1.50 [ 6] Antenna Height (meters, wavelengths if < 0)
      0.00 [ 7] Gain above a dipole (dB)

      ----------------------------------------------------------------------------
      ----


      2. Start VOACAP, select 3_2_GP.ANT as transmitter antenna, and run a
      point-to-point prediction. VOACAP will create a file called GAIN01.DAT in
      the itshf/run/ directory:

      ----------------------------------------------------------------------------
      -------------------------------
      IONCAP #223/2 wl Ground Plane
      2. 30. 0.00 57.41 0.00600 14.00000
      1 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
      0.000
      0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
      0.000
      0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
      0.000
      . . . . .
      ----------------------------------------------------------------------------
      -------------------------------


      3. Move GAIN01.DAT to the HamCap/AntBkup directory, rename it to 3_2_GP.N14,
      then open the file in a text editor and replace the first two lines with the
      header from an existing type 14 file:


      ----------------------------------------------------------------------------
      -------------------------------
      3/2 wl Ground Plane
      3 3 parameters
      0.00 [ 1] Max Gain dBi..:
      14 [ 2] Antenna Type..: 30 x (efficiency + 91 gain values) follow
      14.0 [ 3] Frequency
      1 0.00 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
      0.000
      0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
      0.000

      0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000
      0.000
      . . . . .
      ----------------------------------------------------------------------------
      -------------------------------

      The first line of the header is the antenna name as it appears in the
      antenna selection combo box of HamCap.


      That's it! Now you can test your model in HamCap. To view the pattern,
      select your new model in the antenna combo and click on the frequency button
      to the left of that combo. I must say that the pattern is not very
      impressive, the main lobe in the vertical plane is way too high. A shorter
      antenna would work better, 5/8 wl seems to be the optimum height of a
      vertical.

      The same approach can be used to create models of rotated directional
      antennas, e.g., yagis. Just be sure to set the receiver location due north
      of the transmitter so that it is in the direction of the maximum gain of the
      TX antenna.

      Please let me know if you have questions.

      73 Alex VE3NEA



      > Have just become aware of HamCap & applaud its accuracy & ease of
      > use. The antenna selector is of special interest. Is there a way to
      > address the HF antenna profiles listed in the ITS HF software
      > package? The choices would be most interesting, as my main antenna,
      > for example, is 1/4 wave vertical on one band 1/2 on another 3/2 etc.
      > Plus many of our dipoles are not 1/2 waves. The data seems to be
      > there. How intricate it may be to intertwine them, well.....just
      > askin'...keep up the fine work. 73's Steve KE8PA
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