Amateur Radio Direction Finding and Orienteering
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What is ARDF?
ARDF (Amateur Radio Direction Finding) is like a cross between hidden transmitter hunting (or "foxhunting" as it's commonly known) and orienteering. 5 transmitters, numbered 1 to 5 and all set to the same frequency, are hidden around a course in a bush setting. Each transmitter transmits for one minute, starting with transmitter 1, followed by transmitter 2, all the way through to transmitter 5, and then the cycle repeats. A sixth transmitter on a slightly different frequency is placed at the finish of the course to guide competitors home.
In an ARDF event, competitors are given an orienteering map of the course, on which are marked the start and finish, as well as any out of bounds areas. No clues are given as to the placement of the transmitters. Instead, competitors are equipped with a receiver with a directional antenna to locate the transmitters, and a compass for navigational assistance.
When the event starts, competitors are sent off in small groups every 5 minutes to minimise the "follow the leader" effect. Once started, there is a time limit, typically between 90 and 140 minutes to complete the course. Competitors who exceed the time limit are disqualified.
There are two different ARDF events, namely 2m (or VHF), which is run in the 144-148 MHz amateur band, and 80m (or HF) which is in the 3.5 MHz band. 80 metres is typically easier, as bearings from the receiver are less affected by the immediate environment, and the variation of signal strength is less. VHF is more mentally challenging, with reflections and other local effects confusing the bearings. Because ARDF uses only receivers, competitors don't need to be licences. Anyone can take part, and it only takes minutes to learn how to use the gear. In the Melbourne area, there are usually receivers for hire at ARDF events.
For more details, take a look at the information page on the Victorian ARDF Group's website.
ARDF competitions range from small local affairs to regional and international competitions. I attended the Region 3 (basically Asia-Pacific, for the non amateurs) ARDF Championships in November/December 2003.
Orienteering.
While orienteering isn't an amateur radio activity, it is very closely related to ARDF. In fact, ARDF is sometimes called "Radio Orienteering", which is a very accurate description of the sport. Orienteering itself comes in many forms, of which ARDF is one. Other popular forms of the sport include:
I myself am a regular in the local street orienteering competition, and plan on attending bush events when the season starts.
More Information - Melbourne and Victoria, Australia.
VK3YNG Receivers for Foxhunting and ARDF.
Victorian Orienteering Association
Melbourne Street Orienteering - Why not try an event if you're in Melbourne?
Victorian Rogaining Association
Other Australian sites
Ron Graham Electronics receivers
International Sites
Region 1 (Europe) ARDF Working Group
PB 2 Radio Direction Finding (Netherlands)