Amateur direction finding ARDF, also known as radio orienteering, radio fox hunting and radio-sport, is an amateur radio sport that combines with the map and compass skills of orienteering.
One or two hidden transmitters will be located within a specified area designated by the A3 map supplied. The hidden transmitters may be hidden in diverse wooded terrain, a field, a ruin, or maybe even in a farm building.
Note: that, in the event of a Two Fox hunt, only one station may be audible from the vicinity of the starting point
Equipment Required
1) A 2metre receiver, can be a handheld radio or a receiver specially made for the purpose.
2) A directional antenna such as a Yagi antenna or purpose built variant.
3) Magnetic Compass or Handheld GPS
4) Some means of signal reduction in the case of strong signal reception (an Attenuator)
Rules
1) Each participant is issued with a topographical map of an area of the county in which the fox may be located. The location of the start will be clearly marked. The location of the meeting place for those who have completed the course will also be clearly marked. These will have no relevance to the position of the hidden transmitter.
2) The event will start at a specific Time from an appointed location. All participants must sign in at this location. The event will end at a specified time. All operators will congregate at a designated finish point for refreshments and prizegiving.
3) Competitors must plot their bearings on the map provided.
4) The Fox will make a transmission of 1-minute duration at 5-minute intervals this may be a voice transmission or an Audio CW signal superimposed on the FM carrier.
In the event of a two-fox hunt, the transmissions will be made at alternate 10-minute intervals, Fox 1 will transmit at the top of the hour and Fox 2 will transmit 5 minutes later and so on. Each fox will clearly identify as Fox 1 or Fox 2.
5) Those finding the fox will be issued with a ticket with a time printed on it. The Fox will not give any indication as to whether they have already been located.
6) To qualify as a winner, the map provided, should clearly show the bearings plotted to derive the location of the Fox.
7) Once the competitor has found the Fox, they will vacate the area immediately.
8) If both Foxes have been found the competitor should proceed immediately to the designated finish point which may be a Bar, Restaurant or Picnic Area.
Typical map with bearings drawn in from the Hunter’s point of view – the supplied map will have more detail.
Not always going to be as easy as the map above but this map illustrates the basic idea of taking bearings and finding the Fox. Note magnetic variation must be taken into account when taking bearings.
Naturally, things become more difficult as you get closer in as it is harder to get a bearing on a very strong signal. Signal reduction is essential for the final stages of capture.
There are numerous resources for antenna design and design of the attenuator to be found on the internet. The order of the day is not to make things too complicated!
