[TowerTalk] ground rod depth problem due to rocky soil -- solutions?

[john at kk9a.com]

Interesting data, how long were the seven radials?



To:	 "'Towertalk'" <towertalk at contesting.com>
Subject:Re: [TowerTalk] ground rod depth problem due to rocky
soil -- solutions?
From:	 "K1TTT" <K1TTT at ARRL.NET>
Date:	 Fri, 16 Nov 2012 14:46:47 +0000


List-post:
<towertalk at contesting.com">mailto:towertalk at contesting.com>
I plugged that into my lightning modeling software... if I put 7 radial
wires(NO rods) 1" in diameter (a bit smaller surface area than 2"
strap),
bury it 1' in solid rock (ignoring any advantage of topsoil above the
rock)
and run them out 100' (to equal your 700') I get a ground resistance of
about 8 ohms... as good as 20 rods 8' long by 1" diameter in good
loam...
still sounds like overkill to me.  If I allow for 1' of topsoil on the
rock
with the wires on the rock it goes down to under 6 ohms.   To put that
in
perspective, the 'normal' 2 rods in loam calculates out to over 70 ohms,
in
common clay that reduces to 35 ohms.

David Robbins K1TTT
e-mail: mailto:k1ttt at arrl.net
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