[TowerTalk] lightning

[aa7e@juno.com]

I have just moved from Oregon to central Florida.  As such, I have a
renewed interest in lightning protection.

Coming from the TV broadcast industry, maybe I can inject another issue
on the subject.

As we all know, a square wave contains energy at all frequencies. 
Similarly, lightning contains energy all the way up to 50 MHz or so.  So
often, grounding systems are designed as if all the energy was at or near
DC.  As a case in point, a translator station had a problem with
lightning so they installed a new and "improved" grounding system.  As a
result, the lightning problem was made even worse.

The problem was traced to long lengths of wire between the tower and the
grounding rods.  Although these might have been effective at DC, they
appeared as open circuits at the higher frequencies.

Since the watertable in my local area is 30 feet down, I have been told
that grounding rods need to be drilled down to that level.  I would have
thought that such a system might have the same problem.  I am thinking
that the solution might be to parallel the rods with a copper sheet mat
just below the surface.  This mat would provide some sort of grounding at
the higher frequency content of the lightning energy.  Any comments would
be gratefully received.


73, AA7E


aa7e@juno.com

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