Reprinted from Homing In column in 73 Magazine, January 1997
When did you first hear about radio direction finding (RDF)? Since it has become a tool for finding downed aircraft and stolen cars, today's school kids probably get a vague notion of it early on. Sadly, they aren't told that it can also be great fun for them.
A recent e-mail exchange with Tom Stewart K3TS brought back memories of my introduction to RDF. Tom wrote a classic article about two-meter hidden transmitter hunting in New Jersey for the September 1957 issue of QST. I was 10 years old at the time and studying for my ham ticket, faithfully trying to copy W1AW code practice every night on my drifty Hallicrafters S-38D receiver. That QST issue was one of my first ham radio magazines. Tom's tales of T-hunt trickery got me eager to try the sport.
When my Novice license arrived the following spring, I agitated at the radio club in our town of 11,000 souls to get the group to hold some hidden transmitter hunts. Even though Novices had two-meter phone privileges at the time, we were a hundred miles from the nearest two-meter activity and there were no repeaters to bridge the gap.
Finally, the club scheduled a hunt on 75 meter AM, where most mobile operating was done in those days. I somehow managed to lash together a two-tube 75-meter converter with vibrator power supply and connect it to the broadcast receiver in the family's gas-guzzler convertible. Of course I had to talk Dad into driving. Bemused by the whole thing, he agreed.
For an RDF antenna, I used the multi-turn flat loop from the back cover of an old table model broadcast set. I hadn't learned enough RF theory to do a good job of resonating and coupling it, so it wasn't very sensitive or directional. Dad and I did a lot of riding around just trying to hear a signal over the ignition noise. Fortunately, the hunt boundaries were small and gas was cheap.
Hundreds of T-hunts later, I still think it is the most fun you can have in ham radio. I wish every youngster could experience it. But how many kids nowadays have supportive radio clubs and patient fathers to Elmer them into it? How can we bring kids and RDF together? I think Homing In readers Greg and Gabriella Owens have found an answer.
Greg and Gabriella's letter arrived shortly after Labor Day 1996. They were in charge of a committee from the Simi Settlers Radio Club that would be hosting a Scout Jamboree-on-the-Air (JOTA) campout. They wanted to know how to put on a demonstration of foxhunting (also called radio-orienteering and ARDF) as part of their JOTA activities. What an opportunity!
Greg Owens WA6HKM and Gabriella Owens KE6JQS asked for foxhunting at JOTA-96 in Ventura, CA.
JOTA is a worldwide ham event, held annually in mid-October for almost 40 years. Having never been in Scouts, I knew very little about it. I had no idea if foxhunting had ever been done there before. (Actually, I'm still not sure.) Either way, I knew that this opportunity couldn't be passed up, so I called them immediately.
JOTA celebrations run for a 48-hour period beginning Friday afternoon. They range from simple to elaborate. In some towns, a ham invites a troop or two for a hamshack visit, letting Scouts participate in contacts with other JOTA groups. In other places, it's a full-blown Camporee with many stations and activities. That's what the Settlers were planning.
"We hope to have stations on every active HF and VHF band," Gabriella told me. "We'll demonstrate both voice and CW modes on the air. Local ATVers will set up two stations so the Scouts can have television QSOs back and forth. We will also have code oscillator kits for them to solder together."
The Simi Settlers JOTA site would be Lake Casitas Recreation Area near scenic Ojai, California. Scouts from Ventura, Los Angeles, and Santa Barbara counties were invited. Several hundred could be accommodated. The event would officially begin at noon Saturday and continue for 24 hours. Many Scouts would camp over Saturday night, while others would be at the lake shore for just a few hours on one day. Foxhunting at night would be unsafe, so we had to make it possible for many Scouts to hunt at the same time during our limited available hours.
Lake Casitas is a drive of over 100 miles for T-hunters in my area, but it is only about 40 miles from Santa Barbara, where there is a growing group of radio-orienteering enthusiasts. I own plenty of fox transmitters, but not enough RDF gear for dozens of Scouts to use. What's more, April and I would need knowledgeable helpers for one-on-one training of the Scouts. I zipped off e-mail to Marvin Johnston KE6HTS of the Santa Barbara Amateur Radio Club and he immediately agreed to help.
Having no experience with foxhunting demonstrations for pre-teens, I could only try to envision how it would go. I imagined that we would take the Scouts in packs or troops of a dozen or two and give them a quick show-and-tell on RDFing and map plotting. Then we would hand out some gear and send them into the woods to try to find five foxes transmitting for a minute each in sequence, just like they do in a formal international-rules competition.
Greg surveyed topographical maps for the site and suggested a hilly area of about one square mile across the park road from the camping area. He even agreed to make lots of copies of that map for the Scouts. "Don't worry," he told me, "they are prepared for being in the woods and will bring compasses with them." Good, all I would need for orienteering would be a batch of protractors.
For a week before the event, I spent each evening tuning up my RDF sets and borrowing more. On Friday afternoon, April and I went to the site to check it out. I quickly realized that my imagination had not served me well. The hilly area was fenced off. No access! Oh well, it wasn't very shady. In truth, it looked like a barren home for rattlesnakes. Besides, it was too far away from the campsite.
We decided to hide the foxes within the large wooded JOTA campground, not far from our van where we were showing a video of international radio-orienteering competitions. Scouts would not have a long hike. We could easily watch and help. As a side benefit, the sight of them combing the grounds with sniffing gear would attract much more attention to our demonstration.
April WA6OPS helped explain RDF to eager Scouts before they went out to hunt. Looking on is long-time Scouting supporter Darryl Widman KF6DI.
The two hundred or so Scouts that came to Lake Casitas were mostly in elementary schools. They may be champs at the latest video games, but they had to start at square one when it came to RDF. No way could we simply slap gear into their hands and send them out. It worked best to guide them along in groups of two or three as they learned. One Scout at a time used the RDF set while the others watched. It would then be their turns to find the next foxes.
Five cycling intermittent transmitters proved to be too confusing during the learning process. We changed two of them to be continuous emitters on separate frequencies below 146 MHz, just for first-timers. One was in a surplus ammunition box while the other was the cleverly camouflaged "stud T" (see Homing In for October 1996). That one always got looks of amazement when the Scouts flushed it out. As time and equipment permitted, those who did well on continuous foxes could try to bag the intermittent ones on 146.565 MHz.
To regular users of VHF-FM, it's easy to gauge the strength of incoming signals by the amount of background hiss, or lack of it (quieting). But to a Cub Scout who has never held a handi-talkie before, it's not obvious. After some practice, a few of them did well at getting bearings with an HT, beam and active attenuator. Others couldn't seem to get the hang of it, especially if the HT didn't have an S-meter.
Other types of RDF sets were much easier for kids to learn. The Santa Barbara group brought several dual-dipole homing sets (TDOA type) with left-right indication (meter or LEDs). Although TDOAs are more prone to multipath bearing errors and they lacked signal strength indication, the kids found them easy to learn and had good results.
Reg Reginato KE6ZQY (SK) of Santa Barbara shows a Scout how to use his dual-dipole TDOA RDF set in the JOTA-96 campground.
In Europe and Asia, where radio-orienteering is a popular sport in schools, everyone uses special amplitude-based RDF sets for two meters. There are many variations, but they all incorporate a yagi or phased array antenna and a built-in receiver with wide-range RF gain control. Signal strength is indicated by a panel meter, tone pitch, or tone loudness.
I had only two of these foreign-made sets along, but I think they were easiest for Scouts to learn to use. All they had to do was turn the antenna for strongest signal indication and walk that way. Their excitement grew as signal strength rose and they had to lower the RF gain; it meant they were closing in. Bearings were nearly always accurate.
Weight was the biggest disadvantage of the integrated receiver/antennas. It surprised me how difficult it was for some grade-schoolers to hold a 3-element 2-meter yagi overhead long enough to hunt down a hidden fox. Their arms would become fatigued in about three minutes and the beam would slip down to shoulder high. Of course that adversely affected the beam's sensitivity and directivity. In the future, I want to have lighter antennas with masts, so they can easily be held overhead.
To this Cub Scout, RDF gear seems a bit heavy after a few minutes of fox tracking. Lighter sets and/or mast-mounted antennas may be the solution.
Competitive foxhunters prefer using earphones to hear fox modulation and strength tones in noisy surroundings. That's why most foreign-made integrated receiver/antennas don't have speakers. But phones aren't ideal for one-on-one training. My solution was to have the trainee wear them around the neck instead of over the ears. With gain turned up, they put out enough audio for the trainer, the trainee, and observers to hear. As a bonus, this eliminated the chance of an audio blast directly into the ears if the RF gain control was improperly set when the fox came on the air.
ARDF and kit building were smash hits at our JOTA operation. Lots of Scouts were beeping away on their newly built code oscillators as they came up to the foxhunting display. Some older Scouts said they'd had lots of HF QSOs in previous years, so they were glad have some new activities this time.
Most Scouts had an opportunity to track at least one fox Saturday afternoon. Darkness fell around 6 PM and it was time for a big spaghetti dinner around the campfire. Then we left them for the night, promising to charge up the fox batteries for more hunts the next day.
If there was any doubt that foxhunting enthralled the Scouts, it was dispelled Sunday morning. As we pulled into the campground, we were greeted with young voices shouting, "The fox people are here!" Before we could get the RDF gear out, were mobbed. Scouts who had hunted on Saturday wanted to try again, because the foxes were all in new locations. We gave first priority to those who had not gotten a chance to hunt Saturday; then we let the rest have at it again.
Hats off to the Simi Settlers Radio Club for going beyond the call of duty in providing a special JOTA experience for the Scouts. Special kudos to Greg and Gabriella for paving the way for ARDF events. Also thanks to foxhunting enthusiasts from the Santa Barbara Amateur Radio Club for helping. In addition to Marvin, they were Stephen Nelson KD6VEX, Nerella Reginato, Reg Reginato KE6ZQY, Brian Peddicord KF6DZN, Mike Peddicord KE6OTM, Scott Phillips KF6EDD, Hubert Stamps KC6NAH, Bib Ummels KE6WYA, and President Darryl Widman KF6DI.
Many Scout officials at JOTA-96 expressed interest in future foxhunting demos and activities for their dens, troops, and packs. Given enough inexpensive equipment and trained leadership, radio-orienteering could become a mainstream Scouting activity. I have lots of ideas for gear. But will Scouting organizations across the country be able to find enough T-hunters to get this program off the ground?
Are you Homing In readers willing to build and stockpile some kid-proof ARDF gear, seek out your local Scout leaders, and put on training sessions? I want to hear constructive opinions and ideas from both T-hunters and Scout leaders about this concept. Let's prove that we mean it when we say we want more young people involved in ham radio activities. Send e-mail to firstname.lastname@example.org and let me know your ideas.
Here is an update written for the January 2001 Homing In column about JOTA 2000. There were more Scouts in a more urban setting, so we did it a bit differently.
Future Champs in the Scouts?
Here in Orange County, California, the annual Jamboree-On-The-Air (JOTA) on October 21 was bigger and better than ever. Over 870 Scouts descended on Rancho Alamitos High School in Garden Grove to participate in 13 ham radio exhibits, including HF, VHF, ARES, RACES, ATV, APRS/Packet, CW and hidden transmitter hunting. I put ten foxboxes on the school grounds, ranging from easy-to-spot ammunition cans in the bushes to a tiny micro-T taped on the pipes under a water fountain.
None of the Scouts had ever tried this activity before, so they all needed some quick training. Fortunately, I had some expert helpers, including Tom Curlee WB6UZZ (at left in photo above), co-author of our book on RDF. Also helping was 15-year-old Jay Thompson W6JAY (in photo below) and his father Richard WA6NOL. Both had just returned from the ARDF World Championships in China, where Jay had competed in the Junior Division.
Scouts usually arrived at our foxhunting booth in groups of two or three, sometimes more. We found that a good way to start explaining RDF to them was to point out how it's used to find Emergency Locator Transmitters of downed aircraft. The techniques are similar to those used by biologists tracking radio-tagged animals in nature TV shows that most Scouts have seen.
After seeing how the RDF gear works, one Scout from the group was selected to track a transmitter as the others followed. The youthful hunter got continuous help and encouragement, of course. When he found it, another Scout was selected to find another ammo-can fox nearby. The last hunter of the group, who had received the benefit of watching all the others' mistakes, got to find a well-disguised micro-T for a surprise ending.
For demonstration hunts like this, it's best if the fox transmitters are on different frequencies and run continuously, or nearly so. Short transmissions are OK for experts, but are discouraging to complete beginners. Success for every Scout is the goal, so don't make it too hard.
One-piece ARDF receiver/antenna sets with earphones, continuous tuning, and tone-pitch S-meter are preferred by champions, but they aren't suitable for situations like this. A simple beam, offset attenuator and a scanner or handi-talkie with S-meter works best, because the instructor and everyone in the group can hear the signal and see the meter. This also demonstrates how simple and inexpensive an on-foot RDF setup can be. "Tape measure" yagis are safest for children to carry. See the Equipment Ideas for Radio-Orienteering page at this Homing In site for more information.
Text and photos Copyright ©1996 and 2000 Joseph D. Moell. All rights reserved.
Go to International-Style Foxhunting Comes To The Americas -- How we're getting the ball rolling
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This page updated 9 July 2011