[GreenKeys] OT -- sneak peek -- oops, forgot the pics

[Jim Haynes]

Some guys here made a Doppler direction finder for hidden transmitter
hunting.  Consists of a pair of 2-meter dipoles spaced a foot or two
apart, and in the middle is a tiny little circuit that switches between
them to a cable that goes to a handheld transceiver.  When both antennas
are broadside to the signal source you hear nothing, but when they
are at different distances from the source you hear a tone.  I haven't
got my head around how this works, but the transceiver is FM, so if you
hear a tone I guess it's because there is a difference in apparent
frequency between the signal from the two antennas.