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LRMD ARDF coordinator: Mindaugas Nakvosas, LY5AI
Amateur Radio Direction Finding (ARDF, also known as radio orienteering and radio fox hunting) is a sport that combines orienteering and technical activity, where competitors are searching for low-power radio transmitters (foxes) hidden in wooded terrain by means of a radio direction finding apparatus, map, and compass.
According to the rules issued by the International Amateur Radio Union (IARU), ARDF championships are organized in four formats as follows: foxoring, sprint, and two classic races. In the foxoring race, competitors are searching for continuously operating very low-power transmitters that are clearly audible only within their nominal positions marked on the map. In the sprint race, several groups of transmitters operating at different frequencies are searched for. Each group is comprised of five transmitters operating in short 12 s intervals in sequence (the entire duty cycle amounts 1 min). In the classic races, five transmitters operate in 1 min intervals in sequence (the duty cycle amounts 5 min). In all formats, a continuously operating finish beacon is installed at the beginning of the finish corridor. In the foxoring and sprint competitions, foxes transmitting in the 3,5 MHz (80 m) radio frequency band are used, while in the two classic races, foxes transmit in the 3.5 MHz (80 m) and 144 MHz (2 m) radio frequency bands, respectively. The latter band is specific by the distortion of the propagation of radio waves by landscape relief and inhomogeneity of vegetation and soil; therefore an exact direction to a transmitter might be difficult to estimate.
The foxes transmit their call signs in Morse code as follows: MOE for the first one, MOI, MOS, MOH, and MO5 for the rest four ones, respectively, and MO for the finish beacon. In the classic races, the transmitters are marked on the terrain by an orange-white flag similar to that used in orienteering. In all races, electronic marking devices (IARU recommends SportIdent marking system) or pin punchers are used. The start and finish are located apart. In the classic races, the distances of at least 400 m in-between the foxes, of at least 150 m from a fox to the map edge, and of at least 750m from the start to the nearest fox, respectively, are to be kept.
A winner competitor is identified by all necessary foxes found within a shortest time. Competitors are grouped in several men and women age categories with the different numbers of searched foxes and different minimal lengths of the route. This kind of sport requires endurance training, orienteering (using map and compass) and tactical (establishing an optimal sequence of the foxes searched and finding an optimal route) skills, as well as good controlling of a well-designed direction finding receiver.
In Lithuania, national ARDF championships are being held since 1958. Lithuanian competitors have won numerous awards in European and World ARDF championships.