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[Towertalk] Box forSPG and Lightning protectors

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Subject: [Towertalk] Box forSPG and Lightning protectors
From: (Jon Ogden)
Date: Thu, 19 Sep 2002 15:24:38 -0500
on 9/19/02 2:23 PM, Bill Hider (N3RR) at wrote:

> As I read some of the comments/questions about covering the lightning
> protection boxes, I'm wondering if consideration was taken into account for
> a Single Point Ground (SPG)??
> If the lightning protectors are just laying around on the ground, presumably
> near the ground rod, and then coax or control cables are just run into the
> house without a SPG, what's wrong with this picture?  If that's the
> scenario, you're missing a couple layers of protection.

But if the lightning protectors are all tied into the same ground rod, isn't
that the same as the SPG?
> First of all, a SPG box provides the common ground point ensuring no
> difference in potential even in the face of lightning.
> Secondly, a SPG box made of metal, rather than plastic, provides a Faraday
> shield for all wires passing through the metal SPG box.  A plastic box does
> not.
> Third, a steel box, rather than aluminum, provides a magnetic shield against
> magnetic fields (produced by lightning strikes) inducing currents into your
> cables then entering the house.
Yes, but the box only shields the stuff inside the box.  What about all of
the coax that is run inside the house that is not shielded by any metal?  I
fail to see how a metal box that encloses other metal boxes is going to do



Jon Ogden
NA9D (ex: KE9NA)

Life Member: ARRL, NRA
Member:  AMSAT, DXCC

"A life lived in fear is a life half lived."

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