Tom
Once your shack and tower are separated by about 75' or so, they will
never "see" each other and should be treated as individual entities insofar
as grounding is concerned. The tower should have an extensive grounding
system as shown in Appendix A of our catalog, but I'd suggest another
smaller grounding system be emplaced at the coax entry point where you
would establish your single point ground (where all grounds: equipment,
protector, utility, etc.) are referenced to so as to minimize or eliminate the
possibility of ground loops.
In relatively good conductive soil (which may or may not exist in
the Virginia City Highlands), the inductance of the earth chokes off the
surge energy after 50-75 feet. That's why the tower and shack won't "see"
each other. Soil in these parts tends to be alkaline (do a pH test to be sure),
so copper would be the material of choice. I personally (repeat, personally)
believe hardpan to not be very conductive so ground rods may not be worth
the hassle of installation. The primary purpose of the ground rod is not to
disperse the surge energy per se, that's done by the radial system,
but to find deeper layers of conductive soil and get some of
that surge current to be absorbed by that additional layer.
Even Sylvester Stallone and a pound of C4 would find hardpan the winner.
BTW, Steve K7LXC is quite correct in his posting concerning ground rods
in soil which has been loosened by water etc. However, if you fill the hole
with conductivity enhancing material such as bentonite clay, GEM, or coke
breeze and then hammer the rod into it, it probably would be worth the hassle.
My gods just laugh at me and say "yeah, right!" If they say "No," it must be
extremely softly.
73,
Bob Wanderer AA0CY
Senior Applications Engineer
PolyPhaser Corp.
AA0CY@CONTESTING.COM
----------
From: TOMK5RC@aol.com[SMTP:TOMK5RC@aol.com]
Sent: Tuesday, September 16, 1997 2:58 AM
To: w6old@qsl.net
Cc: towertalk@contesting.com
Subject: Re: (Fwd) [TowerTalk] Driving ground rods
Dick;
I've also received my "welcome" to Nevada, trying to put in my first tower
base. As you mention, after six inches it is rock and more rock. I took a
queue from my elmer, Sam Harris, W1FZJ, who was never encumbered by natural
obstacles. I cut down a pine tree with an 8" base, placed the Rohn base
section over it, secured the tower to the tree with angle iron, placed a 2' x
2' x 2' wooden form around the whole thing and poured it full of concrete.
As far as grounding, I've been reading Polyphaser's literature and will opt
for burying radials instead of ground rods. I'm still pondering the whole
"burying" problem, since I have a 200' run to the shack and I live on open
range with wild horses who love to dig and kick up their heels!.
The saga will continue....
Tom Taormina, K5RC/7
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