[Towertalk] Re: Lighting Protection and Roof Towers & Lightning Rods

[Jon Ogden]

on 12/13/02 12:20 PM, Joe Giacobello, K2XX at k2xx@swva.net wrote:

> I always thought, as Jon describes, that the primary objective of lightning
> protection was to continuously discharge the atmosphere in the vicinity of the
> antenna in order to prevent the build-up of a large enough potential to cause
> a sudden, rapid high current discharge across the air gap.  I always thought
> that was how lightning rods worked.  However, there was a lot of discussion on
> this subject on the Antennas mailing list some time ago, and someone corrected
> me on this description.  Apparently, the mechanism is considerably more
> complex.  I don't remember the details now, but the person who made the
> corrections had pretty good credentials.  (I'm sorry but I don't remember who
> that was.)

It is more complex than that.

But there's two elements of protection.  One is trying to prevent a strike
in the first place.  The second is what to do with the strike energy if one
does occur.

I will not give up my view that half the battle is in prevention of a
strike.  If it was not a valid point, why then is it that guys with properly
protected metal structures up in the air do not get struck, yet the chimney
of their neighbor next door does.  It all has to do with charge build up and
being able to eliminate it.  The properly configured tower system does that.
They guy next door with the metal chimney flue probably doesn't.

73,

Jon
NA9D

-------------------------------------
Jon Ogden
NA9D (ex: KE9NA)

Citizen of the People's Democratic Republik of Illinois

Life Member: ARRL, NRA
Member:  AMSAT, DXCC

http://www.qsl.net/na9d

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