Date: Wed, 28 Jan 2015 17:36:56 -0800
From: Bill Turner <dezrat@outlook.com>
To: Towertalk <towertalk@contesting.com>
Subject: Re: [TowerTalk] Fwd: Antenna to Shack Ground Connection
At the risk of starting a flame war (wouldn't be the first time), I
have to question the purpose of running a ground wire from the tower
to the shack.
What is it you are trying to accomplish? Or putting it another way,
what current are you expecting to flow between your tower and your
shack?
If your tower takes a direct lightning strike, won't a small
percentage of the strike find its way into this ground wire, and since
the wire to earth connection is not zero ohms, some of the strike will
find its way into your shack?
Even if you disconnect your coax and rotator cables during a storm,
this ground wire leaves your shack vulnerable, doesn't it?
Does not sound good to me but if there is a good reason, I want to
hear it.
Bill W6WRT
## I had my electrical contractor buddy..who is also a ham, install
the grnd system for my tower. 3 x 8 ft rods jck hammered into the ground.
Tops of rods are a few inchs below ground. 2 ga wire cadwelded to
each grnd rod. Compression clamps used on the other ends of the 2 ga
wires. crimped with a massive compressive tool. Giant lugs then bolted to
each of the 3 legs of the tower. A ufer grnd can also be used.
## Ok, here we go. A 4th 2 ga bare cu was c clamped..via a special
compression lug
on one of the 3 x tower wires. We used the same c type compression lugs in the
telco I worked at, using a huge 3 ft long crimping tool..and correct die.
Simple way to attach
a 2 ga wire to the middle of another 2 ga wire.
This 4th bare 2 ga cu wire was run from base of tower over towards the
house...and down the
side of the house, all a few inchs below ground..then terminated via a special
cadwelded
4th grnd rod, just outside the basement.
## Yet another piece of 2 ga...this time insulated, was run from same 4th
grnd rod outside
basement window..... through the wall..via 3 inch od pvc.... then to SPG
plate.... which is
just .25 inch thick AL plate, aprx 14 x 18 inchs.
## the reason for the 2 ga wire from tower to shack is to keep em both at the
SAME potential at all times.
Also, another insulated wire run from 200A main breaker panel grnd..... over to
spg plate. Lightning
is trying to find a way ..back to dirt. See K8ri previous comments. Without
the wire between tower
and shacks spg, you can end up with a huge potential difference between the
two items.
## My electrical contractor buddy sez here in BC, that wire from tower to
shack is in the electrical code.
You are in serious trbl if it is not installed. And either a 4th rod driven
just outside shack basement wall,
or your favourite ufer grnd has to be employed, no exceptions. The cadweld
on the 4th grnd rod just outside
the basement wall was a special type, designed to take TWO 2ga wires.
## base of tower.....over to TX equipment is the same deal for commercial
applications, same reason. Electrical
inspector will read you the riot act if its not done to their standards. On
a side note, on commercial towers,
braid / shield of coax has to be bonded to both top and bottom of tower.
Depending on tower height, the braid
is also bonded to tower, half way up the tower. On really tall towers, its
bonded every, I think, 100 ft.
## Im not about to argue with the electrical inspector, end of story.
Jim VE7RF
_______________________________________________
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|