ARRL

Rapid RDFing

I was recently asked to participate in a Boy Scout Camporee and provide a demonstration program of some aspect of Amateur Radio. There was to be a HF station and possibly some other Amateur Radio activities available. Being an active Fox Hunter I thought I could do radio direction finding independent of anything else so I threw my gear in the car and headed off that Saturday morning not knowing what to expect. The first thing I saw upon arriving at the site was the four vehicles in the middle of the field stuck in the mud. So I parked on the road and walked over to the HF station that was being set up. It was at the edge of a small stand of trees about seventy-five feet across. This seemed a reasonable arrangement so I decided to plant the fox on the opposite side of the stand in the tall grass at the base of a few small trees. Returning to the HF station I waited for the fox to transmit then set it to one-minute intervals for the thirty second transmissions to keep things active.

I started to develop a story line that would tie in to scouting to get the interest going. I pulled out my fox hunting gear, hung the compass around my neck, map and HT in hand (see above). It was a quick attraction. As the groups of scouts arrived I handed one of the scouts the custom antenna with a FoxFinder (see QST April 2001) attached, and started the talk with how fox hunting was like Orienteering having map and compass work with the added difficulty that you didn't know were the end point was. Since the FoxFinder is an audio signal strength indicator it was easy for the kids to swing the antenna and hear the signal change without a lot of tutoring. With one or two sweeps of the antenna virtually all of them could give a good direction. Quickly taking turns with the one-minute cycle we projected virtual bearings into the trees.

After a couple of scouts got bearings I moved them part way around the grove and gave a few more scouts a chance with the antenna and FoxFinder.

After three or four locations we estimated a spot where the bearings crossed and walked to the location. Here I instructed the scouts in fox hunting etiquette. Among other things this includes never revealing the location when you think you spot it until every one gets a chance. Even though we were within ten feet at this point no one found it accidentally. After another half dozen tries from within ten feet the location of the fox was revealed. A couple of scouts were able to correctly identify the disguised transmitter, which was remarkable as there was other "junk" around and they had no idea at all what they might be looking for.

I did this with ten groups of four to eight scouts in about fifteen minute intervals without difficulty and not losing any to other diversions.

The scouts caught on quickly to the principle of directional antennas and audio signal strength readings.

The signal strength indication by tone variation was much easier than dealing with radio S meters and attenuators. The near constant activity kept them from losing interest. 

If I were to do this again, I would prepare some schematic maps of the area and have each scout plot some of the bearings the group generated. This would combine some compass skills with basic map skills. Each scout would take home his copy of the map as a memento. And, of course, I would pre-print the blank maps with some Web addresses to learn more about Amateur Radio.