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Re: [TowerTalk] CATV & Phone grounds

To: "'Jim Brown'" <>,<>
Subject: Re: [TowerTalk] CATV & Phone grounds
From: "JC Smith" <>
Date: Tue, 11 Jul 2006 12:45:23 -0700
List-post: <>
Here's a thought (probably mentioned previously).  Assuming a tower has a
good ground system, we still have cables connecting the antennas and other
equipment on the tower to the house and electronics in the shack.  We want
to minimize (or eliminate) any lightning following these cables into the
house.  I know there are fancy commercial systems for this but how about
bolting a 10' length of galvanized pipe to the tower leg and running the
cables through it?

73 - JC, K0HPS

-----Original Message-----
[]On Behalf Of Jim Brown
Sent: Tuesday, July 11, 2006 11:55 AM
Subject: Re: [TowerTalk] CATV & Phone grounds

On Tue, 11 Jul 2006 10:49:32 -0700, Jim Lux wrote:

>How to tie really depends on why you're tying.

Yes. If you think of lightning as DC, you're likely to be in
serious trouble. IEEE studies show that the energy content in
lightning has a broad peak around 1 MHz, with significant
content well above and below that range.

This means that the most important consideration is the
INDUCTANCE of the network of conductors that tie to each other
and complete the path to earth.

To answer the original question -- YES, all of these "grounds"
should be tied together by paths having the lowest possible
inductance. That means SHORT conductors, and WIDE conductors.
As others have noted, braid and stranded wiring is bad because
it corrodes much more quickly than a solid conductor. That's
why wide copper strap is preferred for RF bonding.

Ideally, from a lightning protection point of view, telco,
CATV, power, and our ham antennas should all enter the premises
at the same point so that the bond between them can be very

In the real world, that doesn't always happen, and the bond
between them may need to either run through the footprint of
the house to be short, or must run around the perimeter. That's
another argument in favor of multiple ground electrodes (rods)
around the perimeter of the building, all tied together in a

It's also important to realize that Standards and Building
Codes are influenced by political and financial interests (like
power companies, telephone companies, and CATV companies).
That's why the requirements for bonding of telco and CATV
wiring are so lightweight.


Jim Brown K9YC


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