Capt. H,
From the L-3 (ex-Goodrich, ex-Ryan) Stormscope website:
The Series I ranged storms using the amplitude of the 50 kHz component of the lightning strike. The WX-1000 series uses several aspects of the 50 kHz component (Rise time, fall time, pulse width, etc.) The WX-900, 950 & 500 look at the same aspects of 11 different frequencies to range the strike. In addition the WX-500 & 950 have a “CELL” mode and a “STRIKE” mode, the Strike mode displays the strike similar to the Series I (with radial spread) and the Cell mode uses a more accurate method of ranging the strike.
I was once told that the direction finder approximated a 10 MHz ADF.
The Honeywell system may use a different method as it only shows areas of strikes as symbols rather than the dot per strike of the Stormscope.