This site provides information on ARDF and projects to help the DF enthusiasts equip themselves for a 2m or 80m ARDF competition or even host an event.

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ARDF basics

On-foot ARDF, also known as 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).

It is a combination of Radio direction finding and 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 and a compass and is given an individual start time.

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.

Each transmitter will be co-located with an orange coloured orienteering flag.

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.

A popular 'handy cap' format in the UK is to specify a different number of transmitters to find, (from 3 up to 5), for various age group but with a single results list. The winner will be the one who finds their quota of foxes in the shortest time.
In larger international ARDF events these age categories will be kept separate.

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)

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ARDF for Orienteers

At first sight you may think ARDF is more like tracking animal radio tags or using a metal detector, but remember, the beacons only transmit for a maximum of 1 minute in 5.
You try to estimate your control locations when the beacon is active and then map navigate to, and between them, exactly as you would in Orienteering.  Following a straight line route, as in foot-O, will rarely be the productive option. 

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 the key to becoming truly competitive.

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Why AM?

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 stick with 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.

The availability of simple cheap receivers which are intuitive helps to keep the 'sport' open for beginners, youth and non-amateurs.

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Want to get involved?

The logistics of organizing an ARDF event are much more demanding than a club 2m foxhunt. You will almost certainly 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.

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Home Brew ARDF Projects by G3ZOI

Only simple receivers and QRP transmitters are required for ARDF, so home brewing equipment is economic, rewarding and productive.

All the designs and commercial products on this web site have been extensively field or event tested and more probably both!

Please contact for further details on the availability and pricing of the advertised items. This web site is non-commercial, therefore supplies may be erratic!

2m ARDF Projects

click photos
WB2HOL 3 element yagi TAPE BEAM
ROX-2T 2m integrated AM receiver using the TA7613AP (TDA1083)  
2m ARDF Transmitter
  • Construction details
  • Double sides, through-plated PCB - £6.00
  • PCB with a ICS525R driver chip and Xtal fitted and tested.
     
    144.525Mhz  £12.50
    144.775MHz  £15.00
    others  £20.00 (1st) £15.00 (repeats)

2M TX
Turnstile Antenna TURNSTILE

80m ARDF Projects

click photos
The PJ-80 80m ARDF receiver
  • Low cost- entry level RX from China click here details.
PJ-80
ON7YD 80m ARDF Transmitter and PIC timer ATX80

80m Antenna & ATU
80m Superhet Receiver Kit  (links to external site) RSGB site

Hard-To-Get Components

from G3ZOI.  (only supplied in small quantites to ARDF enthusiasts)
ICS525-01R, User configurable clock multiplier.
Up to 50mW output at 145Mhz using a standard xtal.
These are now available ex-stock from www.digikey.com (10/2009) datasheet
TA7613AP (TDA1083) 1 chip AM/FM radio £2.50 each datasheet
TOKEN 10.7mHz filters  20kHz, 110kHz or 150kHz-£1.00 each datasheet


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