At the restaurant left to right: WB2LRH, KØOV, W6HK, W6SQQ, KD6ONU, AA6DD, AD6XJ. (Photo by KBØZDR)
Weather was beautiful for the fall six-meter transmitter hunt on November 11, 2017. Robert Haggard AD6XJ and Jenna Canillas KBØZDR were the hiders on 50.3 MHz FM, reading from an old QST magazine and trying to keep the transmitter from overheating. Four vehicles left the starting point about 9:50 AM with bearings that were generally north.
First to arrive was the team of Ken Bourne W6HK and Roger Kepner W6SQQ on their first southern California six-meter hunt. The loop led them to overshoot Robert and Jenna's location in east Riverside, but they turned around in Colton and came back. Next to get to the hiding spot behind the Habenero Mexican Grill on University Drive was Will Anderson AA6DD, followed soon after by the team of Joe Moell KØOV and Tom Gaccione WB2LRH. They had gotten into the area some time earlier, but wild bearings led them to thoroughly check out the area near the railroad overpasses to the west before backtracking to the restaurant. A few minutes later, Glen Byron KD6ONU was ready to be talked in, so Robert gave him the restaurant location. Everyone then enjoyed a fine Mexican lunch.
This hunt is scored by mileage, with the lowest mileage winning. Here are the mileages:
KØOV/WB2LRH 16.1 AA6DD 18.3 W6HK/W6SQQ 26.0 KD6ONU DNF
Watch for the announcement of the next hunt, to be held in April 2018.
For competitive mobile transmitter hunts on ten meters and six meters, single-turn loops are the most popular antenna choice. The loop is connected to a suitable portable or mobile receiver through an RF attenuator to reduce the signal for closing in when the S-meter stays at full scale.
The unwanted "antenna effect," where the loop wire picks up the electrical component of the wave as well as the magnetic component, is much more prevalent on 10m and 6m than on 80m. Good loop designs avoid this source of bearing errors by carefully balancing the loop windings around ground or by electrically shielding the loop. More information, plus three designs for 10m loops, can be found in Chapter 17 of THRDFS.
Twice each year (April and November), a well-attended six-meter FM mobile transmitter hunt takes place in Riverside County, California. The transmitter is within a 15-mile radius of the starting point. Hunters try to get to the fox with the shortest odometer mileage. These hunts are organized by long-time 6m enthusiast Will Anderson AA6DD, who has published several designs for 6m RDF loops in his Web site.
Most participants use one of Will's loop designs, but some have sought more weak-signal performance than a loop can provide. I hunt with my 6m shrunken quad (plans in my Homing In column in CQ-VHF Magazine, Fall 2013 issue). Robert Haggard AD6XJ uses his one-of-a-kind 6m Doppler installation. Most of the time, we get to the transmitter more directly than the hunters using loops.
A military surplus loop antenna like this one with a built-in attenuator makes a very simple and inexpensive RDF system for six-meter transmitter hunts.
Will Anderson AA6DD, organizer of the southern California six-meter mobile T-hunts, tests a time-difference-of-arrival RDF set for six meters.
Joe Moell KØOV has found both hidden transmitters and radio interference sources on six meters with this shrunken quad. The taped-up corners were field repairs for broken spreader tip dowels. Next time, fiberglass spreaders!
An optimum four-whip Doppler RDF antenna has the elements in a square pattern of about a quarter wavelength on a side. Robert Haggard AD6XJ uses this Doppler array for six-meter mobile T-hunting. Instead of the usual monopoles, which would have required a continuous ground plane for good directional performance, Robert uses vertical dipoles made from helically-wound whips.
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This page updated 12 November 2017