Foxhunting is an amateur radio activity best compared to geocaching. However, instead of travelling to a set of predetermined coordinates, participants "home in" on a hidden radio transmitter. The beacon constantly broadcasts a beep and an identifying callsign, and using a variety of directionfinding techniques (such as high-gain/directional antennas and triangulation) it is possible to determine the exact source.
Besides being a fun outdoor activity, foxhunting is a very useful skill -- identifying the location of a transmitter is often very valuable. For example, a source of troublesome noise can be identified and eliminated, and tracking the telemetry signal from a fallen rocket booster can be a great assistance to recovery.
The beacon used for our first hunt was a last-minute fix. The original mp3 player used to produce the beacon tone and identification failed, so I managed to rig up a 3DS instead:
The transmitter was a club Baofeng UV-5R, and transmission was controlled by VOX (when the "MP3 player" sent a signal, the radio would key up and transmit it.)
Overall, it was a fun evening, and plans are in progress for a larger, campus-wide foxhunt -- open to the public! Bring your friends (aand your directional antennas).