the strikefinder wasnt designed to find lightning strikes.
what was actually designed was the Automatic Direction Finder (ADF)
which would point a needle toward a distant am radio transmitter.
one of the ADF's weaknesses is the annoying habit of pointing toward
any transmission source on the frequency.
lightning broadcasts intensively on all frequencies during the strike
so the adf swings toward the lightning for the moment that it is
transmitting.
a bright chap designed an adf with a display that could process the
spurious transmissions and display their direction on a screen.

cunning serendipity.
Stealth Pilot