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[Towertalk] creating ground "surround" of house: Obstacle

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Subject: [Towertalk] creating ground "surround" of house: Obstacle
From: (Bill Hider (N3RR))
Date: Tue, 17 Sep 2002 00:56:10 -0400
Good questions, John!
These are typical situations many hams encounter when designing and
implementing a good lightning protection system.

Let me address your questions in the order you posed them:

> I have several questions:
> 1) Should I tie the ground ring around the house to that at the tower
>       I understand that it will be (poorly!) via the coax shield, but I
seem to
>       remember reading that if the tower is a distance from the house,
>       that it was not always desirable to tie the tower ground field into
>       the ground ring around the house.

The short answer to your question is "yes" you should tie the two ground
grids together.
And do it in the way you describe in your posting, with 8' ground rods
spaced every 16 ' apart
until you've integrated them.  It's always desirable to tie the two ground
grids ("fields")
together.  Don't even think of using your coax ground to do this.  Why not?
Well, the idea is to
send the lightning to somewhere else rather than into (or onto) your coax
because the next thing
your coax touches is your equipment, your house, and you (or your guest
operators!)!  So,
the idea is to send the lightning where YOU want it, which is where?  To the
ground - as soon as possible!

Now, sometimes the tower is located so far from the shack (house) that the
impedance in the coax shield
over that long run (say several hundreds of feet) is so large that you'd
think the lightning would dissapate before
it got to your shack.  Well, maybe it would and maybe it wouldn't.  Why not
be safe and provide a path for the lightning
that YOU know is the one you want it to take?  Add that measure of
protection.  In your case, 70 ' just doesn't come
close to being far enough to ignore this, in my opinion.

> 2)   In accomplishing the ground ring around the house, to tie the
>       radio "service entrance" to the house service entrance,
>       I'm going to encounter a section of direct burial Romex that
>       is only about 6" under the surface. It's there to power the septic
>       pump.
>       How should I cross that run? There's really no way to go "around"
>       it. Even though they'll cross at right angles, I'm concerned about
>       inducing voltage into that romex run, and therefore into the house.
>       Should I be concerned?

Yes, you should be concerned, but not for the reason you cite.  The concern
is that you
provide the house grounding "ring" properly.  BTW, the "ring" need not be a
complete ring.  It may
be broken at one point or just be a section of a ring.  Look at my example
of this on my
website:  (I call it a ground grid.)

Based on your description, I'd go under it!  If it's only buried six inches,
just carefully excavate
and install your connecting ground wire under this Romex by about another
foot or so, then back fill it.


Bill, N3RR

> Thanks one and all....
> /John (waiting for the rain to stop!) WB5OAU/4
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