Re: Rock salt and RF grounds (fwd)

---------- Forwarded message ----------
Date: Tue, 14 Jul 1998 07:58:55 -0700
From: Jim Lux <James.P.Lux-at-jpl.nasa.gov>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Rock salt and RF grounds (fwd)

Tesla List wrote:
> ---------- Forwarded message ----------
> Date: Mon, 13 Jul 1998 01:30:50 -0500
> From: Adam Parker <park_e_r-at-hiwaay-dot-net>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: Rock salt and RF grounds
> The other day I talked to someone in the national guard. He said that when
> they install a ground rod they always pour rock salt (Ice cream salt) in
> and around the hole. Anyone ever heard of this?
Adding a conductive substance to the dirt around the ground rod is a
well known technique. I've also seen copper sulfate used. The problem
with salts in general is that they eventually leach out of the ground
rod zone.  You need to keep dumping the salt solution on the ground rod
area to keep the conductivity low.

Somewhere, I saw mention of using carbon black as an additive to
increase the soil conductivity. This might work better.  The idea is to
(from an electrical standpoint) make the ground rod look bigger (larger
in diameter mostly), so that its inductance is lower, and therefore the
induced voltage from a lightning strike is reduced.

"High Voltage Engineering", edited by Khalifa (pub Marcel Dekker, 1990),
has a whole chapter on grounding, with empirical numbers for various
multiple ground rod configurations, as well as a good discussion of
grounding grids.  There are a variety of IEEE publications about
grounding and testing of grounds. Antenna handbooks (particularly those
dealing with AM broadcast stations) also spend a fair amount of time on
grounding because it has a huge effect on the performance of the antenna

Finally, you might want to check out Polyphaser's web site
(http://www.polyphaser-dot-com). They make lightning protection stuff and
grounding is an essential part of lightning protection.