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Re: [TowerTalk] my long lightning story (was RE: lightning strike)

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Subject: Re: [TowerTalk] my long lightning story (was RE: lightning strike)
From: Martin Ewing AA6E <>
Date: Fri, 30 May 2008 12:07:53 -0400
List-post: <">>
Interesting thread.  There has not been too much systematic thinking 
about lightning / surge protection for ham radio, IMO.  Lots of good 
ideas floating around, but too many anecdotal reports.  If you get 
struck, that's a serious anecdote!  But it doesn't help us gauge the odds.

One line of defense I haven't seen mentioned:  avoid the effects of 
external fields (E fields and induction) by building your shack in a 
Faraday cage.  I.e., inside a continuous conductive (grounded) surface.  
(It can be a screen mesh.) This will ensure that the only way bad stuff 
can get to you is through a defined (small) number of cable ports, 
properly filtered.  It's sort of a super single-point ground.  
Expensive, but impressive to your visitors!

The trick for each of us is to balance safety and cost (time and 
money).  Few of us can afford "perfect" protection, and we all live in 
different physical and weather environments.  Many of us gauge our 
protection by eye -- it looks like that ground system is beefy enough, 
it looks like that bend is shallow enough, etc.  Unless we've 
experienced lots of lightning strikes and their effects, or unless we're 
able to thoroughly analyze the E&M problems, we shouldn't trust our 
intuition too much.

We do what we can, but at some point we have to let the insurance 
company take the risk.

My 2c worth.


Martin Ewing, AA6E


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