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Radio direction-finding (ARDF) hunts PDF Print E-mail
Written by Ross Wilkinson   
Sunday, 07 February 2010 23:36

Recalling a series of very successful events run by the Bolton & District ARS in the 1980's, the BWC has now revived this tradition of "Fox-hunts" (light-hearted direction-finding events) in the 2m band.

Following on from G6GVI's seminar on VHF DF-ing, members of the BWC and Bolton RAYNET Group took part in an inaugural practice event on 23-Jun-2008. Blessed by perfect weather conditions in a long light evening, the twenty participants divided into a number of teams and vehicles, and set off to track down the hidden transmitter G0BWC/P (operated by Norman G4YNK).

The teams used a variety of equipment, including 2m loops and small beams, plus the more sophisticated Datong DF1 and Montreal3 phase-detection systems. This practice event illustrated how accurate initial bearings from well-chosen sites can reduce the distance driven in the chase. And apart from learning about VHF-DF techniques, the event was also a very successful social occasion, with most of the competitors staying on at The Beehive (the Fox's lair) for a drink afterwards.

Our second event on 28-Jul again co-incided with a lovely evening, and saw a greater variety of aerials, including a wooden-framed Moxon Rectangle deployed through a sun-roof! Colin G6MRY operated the hidden station near to the centre of Bolton, and "foxed" most of the competitors for a good while. Bill's Montreal3 DF system proved its worth again, bringing his team home first.

For our the third and final event on 11-Aug, the weather stayed mostly dry, and four teams of hunters sought Norman G4YNK who was our "fox" again. Despite wasting ten minutes on a fruitless search for a radio which Ross had accidentally left at the roadside, Ross and Colin managed to locate Norman in around an hour. Although they had the Datong DF1 Doppler system linked to an on-board computer, they relied on bearings from a simple 2m loop and 70cm beam (for tracking Norman's third harmonic once they got close)!

In 2009 we tried some more high-tech options for group DF events, using APRS to co-ordinate bearings from different sites! Read more about this in our Newsletter supplement.

Three more events were held during the summer of 2010, in which fifteen stations contributed more than sixty bearings between them - Jack G8HIK and Paul 2E0TXT being the most accurate overall. But our experience showed that taking bearings on the move with Doppler-type (phase detection) equipment was less susceptible to reflections than loops from fixed sites, so ran a Club Project to build some more of these units for the 2011 season.

But in 2012 we decided to move away from these hi-tech vehicle-based events to a simpler format, where a very low-power beacon transmitter could be hunted in a small area (e.g. a local park) by pedestrian operators using hand-held antennas.


Last Updated on Wednesday, 27 June 2012 19:34

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