[TowerTalk] Sparky Pays a Visit
n2ic at arrl.net
Wed Aug 3 16:41:22 EDT 2005
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 beverages.
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 hill.
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
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