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[Towertalk] bulkhead ground system

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Subject: [Towertalk] bulkhead ground system
From: (Dick Green)
Date: Tue, 23 Jul 2002 19:01:09 -0400

I guess it would be reasonably inexpensive insurance to insulate the copper
plate from the wood with a layer of high-temp fireproof insulating material,
maybe like the rock board they use for parking woodstoves and isolating the
chimney pipe from  the wall (I think this stuff used to be called asbestos
board, but can't believe any asbestos-based products are out there these
days.) However, I didn't see any reference to a fire hazard in all the
Polyphaser material I've read about installing bulkhead panels. That could
be because many bulkhead entries are through concrete foundations. But it's
odd that they wouldn't have mentioned the potential hazard.

Speaking of Polyphaser, they have bulkhead-mount feedthrough coaxial
lightning suppressors that may simplify your job by eliminating the need for
the extra feedthrough connectors. They also sell professional bulkhead
panels, but you can do nearly as well yourself for less money.

I would caution that if the window is relatively high, you are increasing
the panel's distance to ground, which should be as short as possible in
order to achieve the lowest impedance path to ground. Although it's more
work, you might be better off cutting a hole in the wall near the ground. In
fact, one of the Polyphaser books describes an installation where part of
the bulkhead panel is underground and they say this allows a very low
impedance path to ground.

73, Dick WC1M

> -----Original Message-----
> From:
> []On Behalf Of
> Sent: Tuesday, July 23, 2002 1:36 PM
> To:;
> Subject: Re: [Towertalk] bulkhead ground system
> In a message dated Tue, 23 Jul 2002 12:28:24 PM Eastern Standard
> Time, writes:
> > I am considering removing a window in my garage (my ham station
> > sits on the 2nd floor, over the garage) to use as an entry point
> > for all my antenna feedlines and control cables.
> >
> > I am thinking of replacing the window with a sheet of copper cut
> > to the window frame's dimensions, drilling a series of holes for
> > double female coax feedthru connectors to connect the feedline
> > from the antenna outside the window to ICE lightning protectors
> > (the ICE units connected to the feedthru connectors via double
> > male coax connectors) on the garage side.  Copper ribbon will
> > connect the copper sheet to a series of ground rods (and the
> > telco and power gnd systems).
> >
> > I'm looking for comments on this setup before it's built.  Should
> > I be concerned about bolting the copper feed thru panel
> > directly
> > to my garage's wood frame -- is this a fire hazard?
>     Yes. This is the Single Point Ground System main connection
> to ground and any lightning transients will be going through it
> to ground so I'd keep it away from anything that it would arc to.
> Cheers,
> Steve     K7LXC
> Profesional tower services for commercial and amateur

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