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[TowerTalk] Buried #6 copper

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Subject: [TowerTalk] Buried #6 copper
From: (
Date: Tue, 15 Jul 1997 12:20:04 -0500
FR>When I was excavating a long trench to my septic field,
FR>I unrolled a 100 feet of #6 copper in the bottom of the 4 feet deep
FR>trench and connected one of the ends to my tower.

FR>Would this have the equivalency of one or more grounding rods?

FR>    - Frank

The equivalence of 100' of #6 wire compared to a number of vertically
driven ground rods would depend on the soil resistivity..

The only way to qualify is to perform earth resistance checks with
a 3 wire null balance earth ground test and a 62% fall of potential
Measure the ground resistance of the 100' of #6 buried at 4'.
Then measure the ground resistance of a single vertically driven ground
Compare results.,
Results will not be linear, ie adding additional vertically driven
ground rods will
lower the earth resistance but not algebraically.

if a single vertically driven ground rod has a measured earth resistance
10 ohms, adding 3 more will not get you 2.5 ohms.
the results will be somewhere between 4 and 8 ohms depending (again)
on soil resistivity AND ground rod placement.

At my location, 4' down is typically a coarse sand with higher
than the top few inches with organic decay..

The ground system must be below the frost line or during the winter the
earth resistance will significantly increase and will provide poorer
in a lightning storm.

However, most of the lower resistance soil is near the top..

I hope this sheds some light...

Stan, WA1ECF  Cape Cod, MA   FN41sr

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