ARDF Equipment

All you need to enjoy ARDF is a hand-held directional antenna, a radio receiver, and a sense of adventure!

The basic electronic equipment needed for ARDF includes one or more transmitters to locate, and a hand-held direction finding receiver for each participant. ARDF equipment does not need to be very expensive or complicated. Many ARDF enthusiasts begin with simple equipment when they first get interested, then improve their equipment later. Unfortunately, there are few sources in the Americas for commercially-produced equipment designed for ARDF. Fortunately, it is not too difficult to find used or new equipment from Europe, Australia, or Japan, and many ARDF enthusiasts enjoy building their own gear from kits or published designs.

Some specific examples of ARDF equipment, kits, and plans are listed below to help those interested in becoming involved in ARDF. These are not the only options for getting on ARDF. If you think you might enjoy designing or building your own ARDF equipment, Dale Hunt WB6BYU has written an article on ARDF Equipment Design Considerations.


2 Meter ARDF Receivers

The typical two meter ARDF receiver consists of a short hand-held yagi antenna with two or three elements, and a dedicated receiver and attenuator, often mounted on the antenna boom. A short yagi with a boom of ~50 cm (~20") is small enough to carry through the woods, and can be designed to have a clean pattern for direction finding. Many ARDF enthusiasts build these antennas out of inexpensive steel tape measure material that can survive rough treatment in the woods. Two meter receivers can be everything from an HT with an external attenuator, to a dedicated ARDF receiver with built-in ARDF features like automatic attenuation, audio S-meters, and more. In the Americas, most ARDF competitions on two meters use FM transmitters, so having an FM receiver is important.

VK3YNG 2M Receiver VK3YNG Foxhunt 2M Sniffer
This integrated ARDF receiver from Bryan Ackerly VK3YNG is one of the most popular ARDF receivers for two meters. It receives AM, FM, and CW, incorporates an audio S-meter (with stereo headphones,) and automatic-ranging attenuation.
ROX-2 2M Receiver ROX-2T Receiver
D.J. Deane G3ZOI presents schematics, circuit board layout, and enclosure details for a low cost, single conversion two meter ARDF receiver, which is also available for purchase as a kit.
Mizuho FRX-2001 2M Receiver Mizuho FRX-2001
Mizuho is a small Japanese manufacturer of low power Amateur Radio equipment, including direction finding equipment. Finding Mizuho equipment for sale can be a challenge.
Altai 145 2M Receiver Altai 145 2M ARDF Receiver
Altai 145 receivers were commercially produced in the Soviet Union, and were widely used in physical education classes in schools. Available on the used market, it has a rechargeable battery and uses high impedance headphones.
WB2HOL Yagi WB2HOL Tape Measure Yagi
Joe Leggio WB2HOL presents his classic, detailed construction article about building two meter yagis out of steel tape measure material and PVC tubing. These yagis are inexpensive, and rugged enough to handle wooded terrain.
WB6BYU Yagi WB6BYU Tape Measure Yagi
Dale Hunt WB6BYU offers some alternative dimensions for constructing tape measure yagis for two meters. Dimensions are offered for 45 centimeter boom yagis and 60 centimeter boom yagis.
K0OV Attenuator K0OV Offset Attenuator
This offset attenuator design from Joe Moell K0OV provides over 100 dB of attenuation, and is perfect for use with a general purpose hand-held receiver. This is an easy starter project to build yourself.
WB2HOL Attenuator WB2HOL Offset Attenuator
This offset attenuator design from Joe Leggio WB2HOL has a 1 MHz offset and over 100 dB of attenuation. It uses only a few parts and can be built into a small project box.

80 Meter ARDF Receivers

The typical 80 meter ARDF receiver consists of a hand-held CW receiver with a magnetic loop antenna or a ferrite rod antenna attached to it. Most simple CW or SSB receiver circuits for 80 meters will work for ARDF. Magnetic loop and ferrite rod antennas produce a bi-directional pattern, with two symmetrical nulls. Using an additional sense antenna (a small vertical whip) can change the pattern to a cardiod shape with a single (but less sharp) null. Most ARDF receivers for 80 meters use a momentary contact switch to engage the sense antenna when needed.

WB6BYU 80M Receiver WB6BYU 80M ARDF Receiver
Dale Hunt WB6BYU has designed a low-cost, direct-conversion, magnetic loop receiver for 80 meter ARDF that was featured in the September, 2005 issue of QST. Kits or fully assembled receivers are available for purchase from Marvin Johnston KE6HTS.
VK3YNG 80M Receiver VK3YNG Foxhunt 80M Sniffer
This integrated ARDF receiver from Bryan Ackerly VK3YNG is a super heterodyne receiver with an integrated ferrite rod antenna.
WB8WFK 80M Receiver WB8WFK FoxFinder 80
This direct conversion receiver from Jerry Boyd WB8WFK uses a magnetic loop antenna. Printed circuit boards and a detailed construction article are available for this receiver design.
OE6GC 80M Receiver OE6GC ARDF80 Receiver
Harry Gosch OE6GC presents a detailed construction article for building a compact, portable 80 meter ARDF receiver that uses a ferrite rod antenna.
Altai 3,5 80M Receiver Altai 3,5 80M ARDF receiver
Altai 3,5 receivers were commercially-produced in the Soviet Union, and were widely used in physical education classes in schools. Available on the used market, the receiver uses a magnetic loop antenna, and high impedance headphones.
PJ80 80M Receiver PJ-80 ARDF Receiver
This simple 80M receiver with integrated ferrite rod antenna is commercially available in China.

Transmitter Equipment

Hidden transmitters in ARDF competitions usually consist of a battery (sealed, lead-acid batteries are popular,) a transmitter, a transmitter controller, and an omni-directional antenna. On two meters, HTs are commonly used together with horizontally-polarized loop or turnstile antennas. On eighty meters, crystal-controlled transmitters are commonly used with shortened verticals, either hung from a tree or from the top of an extendable fishing pole. Transmitter controllers handle the sending of MCW (on FM 2M transmitters) or CW (on 80M transmitters) and timing the transmit sequence. The entire package can be bundled into a water-tight enclosure such as an old ammunition case or hunter's dry box.

Piccon Controller PicCon Transmitter Controller
This transmitter controller designed by Byon Garrabrant N6BG is ideal for ARDF competitions. It can key transmitters in sequence, can key both CW and MCW, and can be remotely controlled with DTMF tones.
Montreal Fox Controller Montreal Fox Controller
This transmitter controller designed by Francois Tremblay VE2JX and Jacques Brodeur VE2EMM keys both MCW and CW, and features IARU mode, delayed starts, and low power consumption. Printed circuit boards and microcode are available.
ON7YD 80M Transmitter ON7YD ATX80 Transmitter
This design by Rik Strobbe ON7YD is a simple crystal-controlled 80 meter CW transmitter that is popular as an ARDF transmitter.
Montreal 525 2M Transmitter Montreal 525 Two Meter Transmitter
This integrated two meter MCW transmitter and controller designed by Francois Tremblay VE2JX and Jacques Brodeur VE2EMM puts out one watt.
WB6RDV Turnstile WB6RDV Turnstile Antenna for Two Meters
This inexpensive, omnidirectional ARDF transmit antenna is a classic crossed-dipole design with a 75 Ohm phasing section.
AARC Fox Box Albuquerque Amateur Radio Club Foxbox
Check out an example of a complete 2 meter and 80 meter ARDF hidden transmitter box used by the Albuquerque Amateur Radio Club for the 2001 USA ARDF Championship.

For More Information...

Need more ideas for equipment to use in ARDF? Joe Moell K0OV has lots of practical information on his web site, Homing In. Especially worth reading are his articles "RDF Equipment Ideas for Radio-Orienteering" and "Try ARDF on 80 Meters." Joe has also written a book with Thomas Curlee WB6UZZ: Transmitter Hunting: Radio Direction Finding Simplified. Another place to look for ideas is the Direction Finding Equipment Reviews on eHam.net.

 

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Last updated: 26 January 2011
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