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About ARDF

On-foot ARDF, also known as Radio Orienteering or Radio-‘O’, has been popular in a number of countries for many years, particularly in Central and Eastern Europe. The more formal competitions, at both national and international level, conform to rules set by the International Amateur Radio Union (IARU) and use the 2m or 80m Amateur Radio bands.

It is a combination of radio direction finding and foot orienteering.

Five beacons are located in a wooded site and transmit for one minute, in sequence, on the same frequency. A unique call sign identifies each transmitter.
The objective is to work out their locations from radio bearings, devise a route plan and then visit them, on foot, as quickly as possible.

Each competitor has a receiver, map and a compass and is given an individual start time.

The transmitter (usually hidden for security) will be co-located with an orange coloured orienteering flag and a time recording device , collectively referred to, as a control.

At, or near, the time of the departure, the organizer will issue a map (1/10000 or 1/15000) showing only the course start and finish.

A control card is also issued, and must be marked with a pin ( or electronic) punch at each transmitter location as proof of discovery.

Control Flag Photo: approaching a control

The competitor, using his/her receiver, will try to identify the location the various beacons, by taking bearings and optionally plotting them on a map.

Your radio bearings may initially be ambiguous and you will need to refine your route plan as you progressively uncover the location of the controls.

Some will follow bearing directly, others prefer to circumvent obstacles by map reading, and then use well marked paths… it is all is matter of strategy.

Local UK events often offer competitors a choice of a long or a short course, with fewer than the full 5 transmitters to locate. In official international ARDF events, separate courses are determined by age and gender.

On average, the event is limited to 120 minutes. Penalties for going over the limit are very severe. If you do over-time you will be ranked by time alone, regardless of the number of transmitters found !

International events usually take place over two days. One day using 2 meters (144MHz), the other day using the 80 meters band (3,5MHz).

Of course there is no reason why local events cannot use the Radio-O format on other bands eg. 160m or 70cms.

Related links

Orienteering connections

What are differences between Foot Orienteering and Radio-O?

Ideally, the same maps are used, in scale, detail and area coverage. 7500, 10000 or 15000:1 on A4 or A3.

A misconception frequently heard, is that the transmitters are hidden, and found simply by tracking the radio signal, ie. you do not really need to refer to an orienteering map.
In fact, whilst the actual transmitters may be concealed for security reasons, competitors are looking for an orienteering flag located close to the transmitter NOT the transmitter itself.

ARDF is somewhat similar to a score event without the control positions shown on a map.

It is highly unlikely one can simply run the straight line bearing to find the controls in the same way orienteers do not run the ‘crow fly’ lines printed on score-event map. In addition, the transmitters are only active for one minute in a five minute cycle

The initial task for the competitor is to take bearings, at a distance, to approximate the position of the controls and then devise a route strategy to visit them, taking into account the local terrain. These bearings can be just committed to memory, not necessary plotted and drawn onto the event-map.

Only the end-game is somewhat different, as the control does not have to be located on a map feature. When you believe you are close to the control, and when transmitter is active, then you can run towards the signal solely using your receiver. If the transmitter stops, and you have not discovered the control, you might take a compass bearing and continue running-the-compass bearing, just as you would in foot-O.

A lot of time can be lost here, if it transpires you are not as close to the control as you thought !!!

The biggest problem for established orienteers is - it will take 3 or 4 events to master the radio techniques. Unfortunately in this learning period the radio aspect is likely to completely dominate.

If you can persevere, you will be rewarded for your efforts because thereon orienteering skills and fitness will be of great value in becoming truly competitive.

AM for 2m

2m Events in Region 1 continue to use AM for the MCW Morse code signature, in contrast to ’new world’ regions, where FM has been adopted, due to the popular of the FM-handy.
Why AM? It’s primarily a legacy from the long establishment of ARDF in Region-1, but staying with AM has advantages.

Simple manually controlled AM receivers, without AGC, make very good DF receivers. i.e. the volume of the received signal is relative to the signal strength.
A simple cheap receiver which is intuitive to use helps to keep the ‘sport’ open for beginners, youth and non-amateurs.

However, a typical FM receiver modified for foxhunts, will likely be suitable anyway if it complemented with an RF attenuator and some sort of signal strength device. eg. An analogue or audio s-meter.

Get involved

The logistics of organizing an ARDF event are more demanding than a club 2m foxhunt. You may need help to assemble all the equipment and need participants from outside your club to make it worthwhile.
Planning an ARDF event shares a lot in common with traditional orienteering. Establishing contact with your local Orienteering Club, is very highly recommended. Orienteering Clubs will have maps and knowledge of suitable venues. In addition orienteers with a passing interest in technology or Amateur Radio are often keen to try ARDF.

Most Orienteering events are open to all, with ‘colour coded’ courses for a wide range of ages and abilities. Just going an event and seeing the organization, will prove to be a valuable experience. If you feel a little more adventurous, take a compass with you and try a beginners ‘Orange’ course for a taster !

See the British Orienteering Federation web site for more information. (BOF)

Please let the existing UK ARDF community know of your ARDF activities so, they can coordinate a national events calendar.

See the RSGB Amateur Radio Direction Finding Committee Site for more information.