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Re: [TowerTalk] CATV & Phone grounds

To:, "Jim Brown" <>
Subject: Re: [TowerTalk] CATV & Phone grounds
From: Jim Lux <>
Date: Tue, 11 Jul 2006 15:31:04 -0700
List-post: <>
At 12:13 PM 7/11/2006, Bill Turner wrote:
>On Tue, 11 Jul 2006 11:55:08 -0700, you wrote:
> >Yes. If you think of lightning as DC, you're likely to be in
> >serious trouble. IEEE studies show that the energy content in
> >lightning has a broad peak around 1 MHz, with significant
> >content well above and below that range.
>------------ REPLY SEPARATOR ------------
>That raises an interesting question. As I understand it, lightning
>really does flow in one direction, making it DC but having a
>square-wave nature. Is that where the HF component comes from?
>Lightning doesn't really change directions, does it?

The standard model of a lightning impulse is what's called a "double 
exponential" with a fast rise (2 microseconds to peak) and a slow fall (50 
microseconds to 50%).  (i(t) = (1-exp(-t/A))*exp(-t/B) with A and B chosen 
to give the right shape.)

That 2 microsecond rise time gives you the HF spectrum out to the MHz-ish 


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