A couple years ago I had occasion to purchase a FRoG-7 from a fellow, and in 
his vehicle was a DF device that consisted of a small flat box (chassis) 
measuring about 5-8 inches square and about an inch tall with a circle of 10 
(or so) red LEDs on the top and a couple mini-toggles on the rear edge (for 
power, attenuation, etc...). This unit was in turn connected via a cable to 
another smaller box with what looked like large nails (same number as on the 
other box) pointed up through the top of it, and a magnet for mounting it on 
the roof. If anyone has more info (ie schematic) on this, I'd like to give 
building one a shot.  Please, no internet sources.
From what I can figure, the distance between the spikes, and the measurement 
of frequency shift differential (largest change) is the theory behind this, 
correct ?   This project might also be of help to the fellow having problems 
with the jamming SWL'er on his local repeater, that I just read about here in 
the echo.  ;)
Reply here, or direct netmail to 1:2003/7 - Thanks in advance...
All the Best to you and yours,
       Bruce LeGrande
           KB6LWN
           NC2003
--- GEcho 1.11+
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