HFTA does allow selecting 9 combinations of soil conductivity/dielectric
values, but the impact on the gain pattern is relatively small (0.5-1 dB) in
most of the cases I've tried.
Date: Sun, 25 Apr 2010 16:20:32 -0700
From: jimlux <email@example.com>
Subject: [TowerTalk] a fancier hfta
To: Towertalk Reflector <firstname.lastname@example.org>
For those interested in a more sophisticated approach, one starting
point is the 1994 paper by Breakall, et al.
J.K. Breakall, J.S. Young, G.H. Hagn, R.W. Adler, D.L. Faust, D.H.
Werner, "The Modeling and Measurement of HF Antenna Skywave Radiation
Patterns in Irregular Terrain", IEEE Trans. Ant. Prop. V42, #7, July
Abstract is below..
Basically they used GTD with the current distribution in the antenna as
the source. They also (as expected) found that for horizontal
polarization, you can just assume that the terrain is perfectly
conducting (which I believe HFTA does), while for vertical pol, you need
to know what the dielectric properties are.
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