Winter 2010 Issue

Homing In

En Route to Croatia via Ohio

By Joe Moell, KØOV

Vadim Afonkin, KB1RLI, finishes the 2-meter competition on the sand at the 2009 IARU Region 1 championships in Bulgaria. Like most European radiosport enthusiasts, he has a special orienteering outfit that includes gaiters to protect his lower legs from the brush. (Photo courtesy of Vadim Afonkin, KB1RLI)

Did you watch the Tour de France bicycle race coverage last July? It is amazing to see the effort that all of these champions, as well as most regular weekend riders, put into optimizing their gear. Each one seeks out just the right shifters, cranks, hubs, pedals, and saddles to make up a custom cycle that is perfect for him or her.

It is the same way with hams who love on-foot hidden transmitter hunting under international rules, which is called foxtailing, radio-orienteering, and Amateur Radio Direction Finding (ARDF). As they progress in skill and interest, these radio athletes look for gear that is best at giving them useful bearing information without slowing them down while navigating through the forest.

Last time I told you that most radio-orienteers start out on 2 meters with a three-element direction-finding Yagi. Elements are made from a steel measuring tape or another flexible material. These antennas are easy to construct1 and work with any handie-talkie or scanner if you add an offset-type RF attenuator2 to knock down the signal as you approach a fox transmitter.

After a few hunts, some foxtailers “graduate” to a special ARDF receiver with tone-pitch signal indication and automatic attenuation, such as Sniffer MK4 by Bryan Ackerly, VK3YNG.3 Others prefer to stick with manually operating the attenuator, because it gives them a better “feel” of the distance to the transmitter. Are these the same type of people who prefer to drive a stick-shift vehicle?

ARDF can be just a refreshing walk in the park, but winning a medal usually requires some running—lots of it if you are in a category with top-tier competitors. Therefore, your ARDF setup should be designed to be carried safely and efficiently while running. Having the antenna in one hand and the receiver in the other just won’t do. Everything should fit together in a single assembly with a handle that doesn’t require an awkward hand position. You may be carrying it for over two hours at a time, so make it comfortable.

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