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From: pierson@ggone.enet.dec.com (Dave Pierson)
Newsgroups: sci.electronics
Subject: Re: lightning protection question
Summary: the knot can't hurt..
Keywords: lightning, surge, protection
Message-ID: <21931@shlump.nac.dec.com>
Date: 9 Apr 91 17:02:27 GMT
Sender: newsdaemon@shlump.nac.dec.com
Distribution: na
Organization: Digital Equipment Corporation
Lines: 23

In article <1839@eastman.UUCP>, lsls00@iliad.kodak.com (Ilia Levi) writes...
>The reason the loop in the wire should help against a lighting is that
>the lightning is very high frequency, and even a small inductance in the one
>loop coil provides a large inductive resistance.
	Which matches what i have seen, reasonably authoritatively.  Ferrites
would be better, but the knot should help.  The issue is not one of protecting
against a direct stroke, (THATs a very much harder problem) but of reducing
damage from surges induced by that stroke, or surges induced by those surges. 
Even a little inductance will block/slow the surge.  The stroke is limited
time event.  If its resulting surge(s) and their oscillations can be damped,
damage can be limited, mayhap even avoided.

(fwiw, i have seen a sketch for a field expedient coaxial antenna: assume ca 2M
operation:  strip braid from 18" of coax.  Tie knot 18" below the point where
the braid was cut off.  Connect to transmitter.  trim free end of center
conductor, OR move knot to tune.  I have (k)not tried this...)
thanks
dave pierson			|the facts, as accurately as i can manage,
Digital Equipment Corporation	|the opinions, my own.
600 Nickerson Rd
Marlboro, Mass
01752				pierson@cimnet.enet.dec.com
"He has read everything, and, to his credit, written nothing."  A J Raffles