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[TowerTalk] Ground Constants

To: towertalk@contesting.com, topband@contesting.com
Subject: [TowerTalk] Ground Constants
From: Brian Beezley <k6sti@att.net>
Date: Wed, 29 May 2024 12:28:05 -0700
List-post: <mailto:towertalk@contesting.com>
To better represent specific terrain, my HF Ground Constants page now includes an interpolator for the Hagn generic curves. The Hagn HF values are more realistic than the ARRL ground constants offered by antenna analysis programs, which are actually for the AM broadcast band:

http://ham-radio.com/k6sti/hfgc.htm

I've updated my ground probe calculator and the utility that averages ground constants in time or space:

http://ham-radio.com/k6sti/gnd.htm

A 1934 paper sampled soil at depth at a dozen locations in Great Britain. The paper provides enough data to determine the accuracy of short ground probes. Errors of tens of percent at 10 MHz are common, with a few much higher. Errors were < 30% for a trench in Oregon:

http://ham-radio.com/k6sti/gpse.htm

To avoid ground probe sampling error, I took another look at the low dipole method of measuring ground constants. This method samples ground at the proper depth. However, it provides ground constants only for a single band. To overcome this limitation, I tried extrapolating results to the other HF bands with the Messier soil model. It works remarkably well. See the documentation for more:

http://ham-radio.com/k6sti/extrap.zip

Brian

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