Triangulation. Usually only accurate on a groundwave.

Use a loop, make note of the compass heading.Drive 10+ KM to another spot
(the farther the better) and do another compass reading. Repeat for a
third time. Draw the three lines on a map and where they meet, there's the
vicinity of the transmitter.

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca