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

To: Jim Lux <>
Subject: Re: [TowerTalk] ground rod depth problem due to rocky soil -- solutions?
From: Michael Goins <>
Date: Fri, 16 Nov 2012 09:28:12 -0600
List-post: <">>
Impractical analysis because where are you going to get 1" wires and who
could possibly afford 700 feet of it? Plus the cost of getting it a foot
down in rock?

I'm on pretty much solid rock here, 1800 feet up on the side of a hill, and
that would cost a fortune to do.

Still not clear about the need/reason. Why not just totally disconnect and
reconnect the tower when you operate? That's what I do here and the tower
is not grounded other than by its proximity due to the factory base 5 feet
deep in solid rock. My station is completely broken from the tower when I
am not operating and I don't operate in storms. There is nowhere for
lightning to go that would harm my station.

Michael Goins, k5wmg
Professor, Writing
University of Texas at San Antonio

On Fri, Nov 16, 2012 at 8:57 AM, Jim Lux <> wrote:

> On 11/16/12 6:46 AM, K1TTT wrote:
>> 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.
> This brings up an interesting question...  Off hand, I would expect that
> laying a bunch of radials (not too long, but lots of them) of not very big
> wire (AWG14 or AWG12) might be a better lightning ground for the dollar
> than any of the other strategies (except concrete and wire.. great ground,
> and concrete is cheaper than copper)
> Time consuming to install (compared to driving a single rod)
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