The Fox, the Hounds, and Amateur Radio
The methods used to determine, at a distance, the source of a transmitted signal, are broadly as direction finding (DF), and have application in navigation systems. But radio amateurs also effectively use DF when they take part in a popular activity called Foxhunting. This involves locating within a time limit a small hidden transmitter.
In some countries DFing is called Radio Sport, and involves a lot of footwork over reasonably lengthy courses, and is likened to a mix of DFing and another sport - orienteering. However Foxhunting in Australia often includes travel in a car, and DFing a hidden transmitter while on the move. Then the Foxhunters, or Hounds as they're known, become pedestrians to discover the hiding spot of the transmitter, and you guessed it is called the Fox. Foxhunts can also be held over relatively short courses requiring Hounds to do all of their DFing while on foot.
How is it done?
Foxhunting basically uses a directional beam antenna, both vehicle mounted or out-the-window, and receiver to DF the general hiding spot of the Fox. Then most Hounds use a special receiver called a "Sniffer" with variably sensitivity, to virtually sniff out the Fox. Numerous cunning tricks are played by those hiding a Fox as they seek to elude the Hounds.
Regular Foxhunting Championship series are held all over Australia during the Foxhunting season. A dozen or teams join in. Enthusiastic newcomers are often able to find the Fox ahead of some of the more experienced competitors.