[TowerTalk] Ground question
jim.thom at telus.net
Thu May 10 13:02:58 EDT 2018
Date: Wed, 9 May 2018 19:39:14 -0400
From: "Larry Banks" <larryb.w1dyj at verizon.net>
To: "Terry Brown" <n7tb at comcast.net>, <towertalk at contesting.com>
Subject: Re: [TowerTalk] Ground question
<I believe that radials 16" deep will be great for lightening protection, but
<not for RF -- they should be on or near the surface. As for how many, this
<is a good reference, from the ARRL Antenna Book:
### It appears he is installing a simple 35 ft rohn 25 tower. He never mentioned
anything about using it as a vertical, or shunt feeding it etc.
## He described what appears to be a gross overkill lightening protection setup.
For lightening protection, 2 rods would suffice, close to base of tower, then u have
a redundant ground rod. Then perhaps his proposed buried radials. Like
10 gauge solid copper, or 8 to 10 to 12 gauge bare stranded copper. And
perhaps 2-6 radials.
## for lightening protection, and if any radials used, they have to be below the frost line
for your area...and bare solid or stranded copper.
## Last time, eons ago, that I saw an AM broadcast tower array, they used 10 gauge,
solid bare copper, laid on the ground. 120 of em...and .4 wave lengths long. A ring
of 10 ft long copper ground rods close to base of tower provided the actual lightening protection.
Then 2 gauge, bare, stranded copper from each ground rod back to base of tower. Tower used
an insulated base.... with a lightening ball gaps, one bonded to base of tower..just above the insulator,
2nd ball was bonded to the ground system buss, where all the 2 gauge copper wires were bonded to.
Cadwelded at the top of each rod...and top of each rod was slightly below ground level. Then the
120 radials were on top of that mess.
## I used 3 X 8 ft copper clad steel ground rods at base of tower. Then 2 gauge stranded and insulated
RW-90, cad welded .... back to tower base. Then bare 2 gauge stranded copper, from base of tower, buried
in garden, alongside the house.... back to a 4th ground rod just outside basement window. Then routed to SPG,
just inside the basement. SPG is just .25 inch thick Al plate, aprx 12 inches tall x 20 inches wide. Some scrap
stuff I had laying about.
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