Radio Direction Finding, AKA Foxhunting

If you’re thinking amateur radio is just about sitting at your desk and making contacts with other hams, there’s a whole lot more to it. One of the fun things we can is as a form of “radiosport” called foxhunting. It uses radio receivers to locate a transmitter at an unknown location.

Typically, directional antennas are used to home-in on a signal, allowing you to get a bearing, move in the direction from which you think the signal is coming, then listen in and adjust your bearing until you (hopefully) arrive at the transmitter location. The first one to find the transmitter wins!

This activity can be done on foot or with the use of vehicles to allow quick movement toward the transmitter. In the case of a mobile operation, you either use RDF antennas in/on the car or pull over and stick an antenna out the window every so often.

You can build your RDF gear or buy it pre-made or in kit form. Check out this page for some resources or do a web search to learn more.

RDF is used for more than just fun. It is also used to track wildlife, locate sources of interference (1, 2), find stolen cars (LoJack), or for search and rescue. If you ever had reason to track radio frequency interference (RFI), it would sure be nice if you’d already had some experience with direction finding so the process was familiar.

Here’s a good video that shows a competition in progress and gives a good idea of how the process works. It was produced by KN4AQ, who has a series of YouTube videos under the title HamRadioNow.

Here’s a link with video of a practical use of RDF for tracking down power line noise – the noise coming from some broken piece of equipment on a power pole (like a cracked insulator causing arcing).

 

Additional Reading:

https://en.wikipedia.org/wiki/Transmitter_hunting

https://en.wikipedia.org/wiki/Direction_finding

http://www.homingin.com/ – all about foxhunting

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