Topband: lightning

[Carl K9LA]

Bud W2RU asked: What is the usual tilt, if any, in T-storm noise across 
160m?

That depends on the time domain response of the lightning discharge. If 
we assume a typical pulse (rise time of around 100 microseconds, peak 
current of 20,000 amps, and a fall time of around 10 milliseconds) and 
transform that into the frequency domain, we'll see the noise amplitude 
gradually rising all the way down to a couple hundred KHz and then kind 
of leveling off. The difference between the low end of 160m and the high 
end of 160m would be only around 1 dB (all of this comes from a 
WorldRadio column I wrote in June 1999).

Bud also asked: Is it consistent from storm to storm?

That is a tough question. Maybe someone else has some statistics on the 
variation of the time domain response of lightning discharges. I would 
think in general that the high end of 160m would normally be exposed to 
the lesser T-storm noise - but it doesn't appear to be that much of a 
difference. Of course Mother Nature would have the ultimate say here.

Carl K9LA