[TowerTalk] Sparky Pays a Visit
kdutson at sbcglobal.net
Wed Aug 3 13:56:50 EDT 2005
It has been said many times before but is worth repeating: make sure your
system ground is tied to the AC service entrance ground. It's always best
to tie all components to this ground. What typically kills electronic
equipment is current flowing from one ground to another.
73, Keith NM5G
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of Steve London
Sent: Wednesday, August 03, 2005 3:41 PM
To: towertalk at contesting.com
Subject: Re: [TowerTalk] Sparky Pays a Visit
So, just for amusement, let's see what folks would do in my situation...
I live on a very dry hilltop in SW New Mexico. There are large limestone
boulders at the surface, or within a few inches of the surface. You don't
dig in this stuff with a shovel or backhoe - it takes a jackhammer or
excavator with a jackhammer attachment. There is no moisture in the ground,
except for a few days after a monsoon rain event.
For what small good it might do, I have ground rods at each end of my
The deepest I could get them was about 2 feet. The resistance between the
ground rods (which are about 500 feet apart) is around 5M ohms. We're
talking DRY here !
Frankly, what the local power company does for grounding seems worthless.
They drill a hole in the ground for their pole, run their copper ground wire
to the bottom of the pole, loop the copper wire in a spiral around the
bottom of the pole, and plop the pole in the ground. With no moisture in
the ground, I can't believe that does anything. When my house was built,
they didn't even try to drive in a ground rod, they just used the rebar and
concrete in the foundation as a Ufer ground. I understand that is okay for
safety grounding, but completely worthless for lightning protection.
Now, as far as radio goes, I have a 105' guyed tower, about 100 feet from
the house, and two 30' guyed towers about 30 and 50 feet from the house.
The tall tower has the typical Rohn-approved concrete base and guy anchors.
No ground rods, buried copper wires, etc. All of the cables, from all of
the towers run on top of the ground, and terminate at an aluminum plate
("bulkhead") located about 30' from the house. There is a separate set of
cables that can be connected to the bulkhead connectors, running
underground, through plastic conduit, to the ground-floor hamshack. When
the hamshack cables are not connected to the bulkhead, they sit in a covered
plastic bucket, about 3 feet from the bulkhead. The bulkhead is not
intentionally grounded or connected to the house Ufer ground. My strategy
is simple - I don't care what happens on the tower, but keep the lightning
out of the house.
I haven't had a direct hit yet, but that's only a matter of time on this
It does make me feel like I'm playing with a loaded gun !
So, short of doing a major excavation to lay a circle of copper tubing
around the house and bonding everything to it, what might make sense to
protect the house ?
Steve London, N2IC/5
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
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