on 9/19/02 2:23 PM, Bill Hider (N3RR) at n3rr@erols.com 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
much.
73,
Jon
NA9D
-------------------------------------
Jon Ogden
NA9D (ex: KE9NA)
Life Member: ARRL, NRA
Member: AMSAT, DXCC
http://www.qsl.net/ke9na
"A life lived in fear is a life half lived."
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