[TowerTalk] Ground question

Jim Thomson 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

<Hi Terry,

<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. 

Jim   VE7RF   

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