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
TowerTalk mailing list