How does a stormscope/strikefinder actually work?

Okay, this question is just about curiosity and the remote possibility
of an interesting DIY project. I'm an EE, so have the background do
understand (but working in the computer field, may not have the recent
experience to do so.

Just how do lightning detection systems work?

It seems to me that the E/M discharge from lightning is essentially
noise, and so would be rather wide-band. So one could easily detect
that a static discharge had occured by looking for a sudden
simultaneous burst of energy in two or more rather disparate frequency
ranges.

But finding where the discharge was... that seems harder. Clearly, one
filter out one band of frequency and use direction antennas and a
little math to figure out the azimuth to the strike.

So now we have a way to detect a strike and work out its angle
relative to the receiver.

But how do you get distance? All I can think of is having multiple
antennas on the aircraft, separate by some known distance, and using
simply time-domain analysis to convert the relative time of flight to
each of the antennas into a position. This would seem to require at
least three antennas to work, and also would require an uncommonly
precise way of measuring time considering that you can't get antennas
very far away from each other on a light aircraft.

So, how do these devices _actually_work? What frequency ranges do they
work in? How many antennas do they have? How do they determine
distance?

thanks,
Dave Jacobowitz

-- jacobowitz73 --at-- yahoo --dot-- com