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Re: [Amps] Terrain Mapping for EZNEC ( Again )

Subject: Re: [Amps] Terrain Mapping for EZNEC ( Again )
From: Jim Brown <>
Date: Sun, 14 Dec 2014 21:21:24 -0800
List-post: <">>
On Sun,12/14/2014 12:59 PM, wrote:
Several months ago, someone recommended a mapping program that looked at the near field ground around a tower to predict take-off angles and ground reflection gains.

The only one I know about is HFTA (High Frequency Terrain Analysis) written by N6BV, and distributed the the CD with the ARRL Antenna Book. It predicts the interaction of HORIZONTALLY polarized waves with terrain. It has a learning curve, it can be tricky downloading the needed terrain data from government websites (but it's free), and it can take a lot of work (I spent months) to get a useful set of predictions for all the bands and for several possible antenna sites, but many of us here in the interesting terrain that California provides swear by it (me included).

Dean, N6BV, did a very good WebEx tutorial several years ago, that is, I believe, still on the PVRC website. Buy the ARRL Antenna Book, and study the parts of a chapter that explain the concepts and how the program works. Then watch the WebEx.

Note that this program does NOT work for vertically polarized waves because they interact very differently with the earth. I asked Dean about the practicality of writing something for verticals, and he indicated that a major roadblock is the availability of sufficiently detailed data on soil conditions. Turns out that data is useful for mining, so you gotsa pay for it, and it ain't cheap.

73, Jim K9YC
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