"SR" wrote in message
...
Ok so it was like a LORAN system.

SR


No, LORAN uses time measurement.

A Radio Direction Finder basically points in the direction of a LW or MW
radio station.
Have you ever used an old AM radio with a ferrite rod antenna inside? If you
turn the radio around the signal drops out if the end of the radio is
pointed toward the AM broadcast antenna.

Old direction finders used big circular crossed loops, now ones use a block
of ferrite with two windings on them at 90°.
With a combination of signals driving servo amplifiers, it is possible to
drive a device called a Goniometer to a null position, ie no signal, then
read off the bearing.
With a bit of practice, you can do the same thing with an old transistor
radio. BUT - they aren't very accurate. 4 or 5 degrees was considered
excellent. If you are trying to get a bearing on a distant station, be sure
you are using the groun wave, as the ky wave can distort and come in from
different angles.

Most modern aircraft carry an ADF receiver, but some are being removed in
favour of GPS.

Brad.