Fox-Oring

Fox-Oring is a form of Radio-Orienteering or Amateur Radio Direction Finding (ARDF). It differs from standard ARDF compared with which fox-oring could be considered to have more orienteering involved.

	Fox-Oring Control

A fox-oring event operates in a similar way to a score event and typically there are about 10 controls. There are no nationally or internationally agreed rules for Fox-Oring at present and so although the general principles remain the same the details vary between different events.

At each control there is a low power transmitter which can be received within about 100 to 200m from the control. At some events the transmitters will be operating continuously whereas at others each will transmit for a certain period of time during each minute. All the controls transmit on the same frequency and usually each transmits a different letter in Morse code (slowly) so it is possible to tell them apart. The controls themselves are made less conspicuous than a normal orienteering control; often there will be no flag (and if there is one it will be small).

The map looks like one for a normal score course with each control marked as well as the start and finish. However, the location given for each control is only approximate – the control itself is not at the centre of the circle and may even be outside it, but it will be positioned so that it is possible to receive it from within the circle. There are no control descriptions and controls are not necessarily on mapped features.

The competitor needs to select which controls to visit, in which order and navigate to their vicinity in the same way as for a normal score event. It is at this stage that the radio part comes in for finding the exact location of the control.

3.5 MHz DF Receiver

All Fox-Oring events in the UK use the 3.5 MHz band. Receivers used for this band are fairly compact and have two antennas – a ferrite rod (like in a MW radio) and a whip. (The receivers you may have seen with large antennas made from tape measures are for a different band – 144 MHz). Most of the time only the ferrite rod is used, this has the characteristic that there is a strong null when the rod is pointing towards the transmitter. This gives an accurate bearing but with a 180° ambiguity. To resolve this the whip is used, pressing a button (called sense) combines the two antennas and this configuration the signal is strongest with one side of the receiver facing the control (usually marked with an arrow) but it is not possible to take an accurate bearing. Using the sense also makes the receiver more sensitive which can be useful when some distance from the control.

At the simplest, once you are close enough to the control to hear it you follow the direction given by the null and will reach it. This will work reasonably well where the controls transmit continuously, the terrain is uniformly runnable and the controls are widely separated. In other cases other skills become useful such as estimating the distance to the control from the signal strength.

Over the last few years there has been roughly one radio-orienteering event each month in the UK with a few of these having a fox-oring course, so there have been fairly limited opportunities to try it. In 2009 it is planned to run a number of Fox-Oring events which will be aimed at beginners, which are likely to be mainly in the summer. There will be a supply of receivers available at these events so it is not necessary to have any special equipment to take part.

Details of all radio-orinteering events in the UK (and some further afield) can be found at http://www.ardf.btinternet.co.uk/events.html.