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Re: [TowerTalk] 16om vertical and the number of radials

To: towertalk@contesting.com
Subject: Re: [TowerTalk] 16om vertical and the number of radials
From: Brian Beezley <k6sti@att.net>
Date: Sat, 3 Dec 2022 10:21:41 -0800
List-post: <mailto:towertalk@contesting.com>
Paul, W9AC: "Isn't the measured probe result only useful for near-field system efficiency analysis? By near-field I mean to obtain system efficiency within a wavelength or so of a vertical radiator.
But for skywave propagation field strength, don't we also need to know 
more about the ground conductivity much further out to more than 1km on 
160m?"

Paul, I don't know how distant ground affects 160m specifically. But if you're on a hilltop, at low elevation angles your signal may reflect or diffract from ground miles away. Its permittivity and conductivity might be quite different than that of the ground beneath your antenna.
I think the main usefulness of knowing your ground characteristics is to 
predict antenna efficiency. That could easily determine your choice 
between a horizontal and vertical antenna on 80m or 40m.
If you have some idea of the ground quality far away, you could create a 
separate model with that value to study low-angle effects. You could 
take a drive and go measure distant ground. But you'd probably have to 
take a number of measurements to satisfy yourself that you had a 
representative sample. My ground probe calculator includes a utility 
that will average probe measurements. I had in mind making multiple 
measurements near the antenna, but you could use it to create an average 
of far-away ground for a low-angle model.
Brian
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