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 Previous: ARRL First VP Chairs Global Amateur Radio Emergency Communications Conference |  Next: Icom to be 2006 ARRL November Sweepstakes Principal Awards Sponsor |
By Joe Moell, K0OV
ARRL Amateur Radio Direction Finding Coordinator
Contributing Editor
August 16, 2006
Looking like porcupines on steroids, SUVs and other vehicles bristling with antennas gather on hilltops every weekend. What's going on?
 A simple cubical quad on a window mount is an excellent way to get started in mobile T-hunting. Crystal Melhorn, W9IOU, and Anthony Boudreau were the winning team at the Kankakee Amateur Radio Society's T-hunt during the 2004 CQ National Foxhunting Weekend. [Clay Melhorn, N9IO, Photo] |
 Dick Arnett, WB4SUV, demonstrates his setup for mobile T-hunting in the Cincinnati area. He has a rotating beam with a CRT polar strength-versus-direction display. His Doppler unit is on the dash at far right. [Joe Moell, K0OV, Photo] |
As ARRL's ARDF Coordinator, my mission is to spread the word about on-foot transmitter hunts, especially ones using the internationally coordinated rules that make national and worldwide competitions possible. I have the privilege of working with national coordinators in Canada as well as in many countries of Europe and Asia.
But there's another kind of transmitter hunting that I don't coordinate. It has been going on in the US for much longer, in more localities, and with more participants. Many hams in the Eastern US call it "foxhunting," but in California, it's "T-hunting." Most hams have heard of it, and many have tried it, but few are aware of the intense interest in this radio direction finding (RDF) sport among hams in such places as Los Angeles and San Diego.
Mobile T-hunting made news on Memorial Day weekend, when two long-time participants lost their lives in a single-vehicle accident. Based on some posts in message boards afterward, it appears that many hams think these T-hunters were doing something unusual and dangerous. Unusual yes, but dangerous, no. T-hunting might be an "extreme sport" for ham radio, but in this case it was no more risky than driving a narrow mountain road. As a mobile T-hunter in southern California for 30 years, I want to fill you in on this fascinating specialty of our hobby.
All-Day Means All Weekend
After many years on 75 and 10 meters, mobile
transmitter hunts moved to 2 meters in the 1950s. This was the era of AM voice
with "Gooney Birds" (the Gonset Communicator series) and "Benton
Harbor Lunch Boxes" (Heath single-band transceivers). The sensitivity of
these "hollow state" (ie, vacuum tube) sets was just good enough to
give about a mile of mobile-to-mobile range in the city. The bulky rigs and the
batteries/power supplies necessary to power them weren't easy to conceal, so
most hunts ended up with everyone converging on a parked vehicle. Occasionally,
an enterprising "hider" would attempt some camouflage in a baby stroller or
traffic-counter box.
 Mike Obermeier, K6SNE, who died while T-hunting in May, loved to build unique mobile RDF systems. This was one of his first, in a converted mail truck with steering wheel on the right side. [Joe Moell, K0OV, Photo] |
 Most southern California T-hunters have switched to SUVs, but the author still likes his minivan because there's room for both a rotating quad and a Doppler array on top. Note the hole in the roof for the rotating mast, with rain deflector. Atop the quad is a fluxgate sensor for the polar bearing display inside. [Joe Moell, K0OV, Photo] |
By 1980, solid-state FM transceivers with ever-increasing sensitivity became affordable. A new era in T-hunting began, as one club or another staged a mobile hunt in the Los Angeles area almost every weekend. Typical boundaries encompassed from 80 to more than 3000 square miles of urban, suburban and rural terrain. Transmitters were buried, placed in trees and hung from bridges.
But this wasn't quite enough intrigue for some of the hunters. Why not take boundaries to the limit? With this, the "All-Day" hunt was born. There has been one on the fourth Saturday of each month ever since, usually starting from a 1200-foot hilltop on the Palos Verdes Peninsula, south of Los Angeles.
All-Day hunt rules are simple. The hider must provide a huntable signal, meaning that the hunters can detect it with their long Yagis, GaAsFET RF preamps and multimode 2-meter receivers at the starting point. Boundaries are the continental US. This means no transmitters in Mexico, on boats off the coast or on Catalina Island! The winner is determined by start-to-finish odometer mileage (lowest wins), not by time. This encourages safe driving and careful plotting of bearings.
At first, All Day hunts had only one transmitter to find. Later, multiple-T hunts became the norm. One high-power T gets hunters into the area, with several lower-powered Ts along the way or within a few miles of the main T.
Mobile T-hunting is usually a team sport. A few prefer to hunt alone, but in most cases there are two or three in the car, truck, van or SUV. (Here's an opportunity to get the whole family involved!) The navigator -- which some laughingly call the "navi-guesser" -- rides in the right front seat and keeps track of incoming signal direction, trying to be as accurate as possible even when whizzing along in the fast lane of a freeway. He or she plots bearings on paper maps or a GPS-augmented computer and attempts to predict where the transmitter is and how to get there. This allows the driver to safely concentrate on the vehicle and the roads.
At the start of a 2-meter mobile T-hunt in my area, you will see a wide variety of RDF equipment, much of it home-built. Hand-rotated Yagis and quads are traditional, the mast usually protruding through the vehicle roof. That's right! There's usually a hole of one or two inches diameter in the center of the roof, with provisions for weatherproofing. This allows maximum boom length without overhang and makes it easy for either driver or navigator to turn it. A simple setup with such a beam, an RF attenuator for closing in, and a receiver with S meter is inexpensive and surprisingly effective.
A few teams employ no-moving-parts Doppler RDF sets, sometimes linked to a mapping laptop. Dopplers can catch and hold the direction of short-duration signals and are advantageous when bearings change direction quickly as the team closes in. This high-tech approach is fun to use, but it has a big sensitivity penalty due to lack of gain in the antenna system. In southern California, where hidden transmitters have weak signals because they are in canyons and behind hills, the Yagi/quad hunters defeat the Doppler hunters as often as not. Some teams make up for this by putting both a beam and a Doppler set in their arsenal.
 Another way to have a Doppler and beam on one vehicle is to put the Doppler's elements around the beam's mast, as this hunter in San Diego County has done. Keeping effective separation means that the beam has to be high above the vehicle. [Joe Moell, K0OV, Photo] |
DX Records
In the 1990s, All-Day T-hunters stepped up the competition to see who could hide farthest from Rancho Palos Verdes and still provide a huntable signal. J. Scott Bovitz, N6MI, and Milt Ronney, WA6FAT (SK), thought they had a permanent record when they launched a signal from the top of 8351-foot Shuteye Peak in the Sierra National Forest in 1989. Their Madera County location was 252 air miles from the starting point.
Not to be outdone, Jim Forsyth, AF6O, and Eric Nansen, N6YKE, decided to immortalize themselves by increasing this record by 36 per cent in 1993. Jim said that a lucky QSO alerted him to the possibility. "The month before, a T-hunt coincided with the January VHF contest. We ended up on Table Mountain looking for the hidden T, which wasn't there," Forsyth explained. "While near the peak, we decided to work a bit of the contest. We came across a guy who was putting in a strong signal from Utah."
"He told us that from Utah Hill, he regularly worked people in Los Angeles and Orange Counties," Nansen added. "Jim told everybody that we had found our spot for the hunt on this outing, which led them to believe we would be near Table Mountain, only 59 miles from the starting point."
 For an All-Day hunt in the early years, Deryl Crawford, N6AIN, put this setup in an almond grove in central California. He managed to get the signal across the 150-mile path to the start point by knife-edge and multipath propagation through the intervening mountains, some of which are 8000 feet high. [Joe Moell, K0OV, Photo] |
Utah Hill is along a stretch of old US Highway 91 from Littlefield, Arizona, to St. George, Utah, passing by Jarvis Peak. "At 4724 feet elevation, it looks right down on the Grand Basin," said N6YKE. "Except for a little ridge in the valley, we had 2500 feet elevation over everything between us and Las Vegas and beyond."
On the day before the hunt, Eric and Jim went to their undisclosed spot to test with Clarke Harris, WB6ADC (SK), at the Palos Verdes starting point, keeping in touch on 40-meter mobile SSB. They transmitted 600 W into a 15-element KLM Boomer Yagi for an hour and a half with no success. Then they moved their setup down the hill about 150 feet. Immediately, WB6ADC heard them clearly on 2-meter FM with his T-hunting quad over the 344-mile path.
A successful test doesn't necessarily mean a successful hunt. Two meter propagation over this distance varies with time of day and weather, and the weather was changing. "On hunt day, we encountered snow at 3500 feet on the way to the site," said Jim. "It turned out to be no problem driving there because it was melting fast. Propagation peaked before start time, but the hunters heard us OK."
One very distant transmitter was not enough for these two. They put out three others along Interstate 15 for the hunters to find, or perhaps forget to find. T #2 was on Kelbaker Road, 0.4 mile south of the freeway off ramp at Baker, California.
The third T was on Highway 169, which run south from I-15 to Lake Mead at Overton, Nevada. According to AF6O, "It was hidden on the northeast side of a hill with a beam pointing at Mormon Peak, a 7411-foot mountain. As you headed northeast on I-15, you couldn't copy the direct signal. All you heard was the reflection from Mormon Peak. Quite a few hunters got fooled by that."
The fourth T was near the I-15 Virgin River Gorge rest area in Arizona, nine miles beyond the Highway 91 exit to Utah Hill. "You had to get off at the rest stop and take a little dirt road on the opposite side of the interstate," Nansen said. "People were 'sniffing' at the rest stop because its beam antenna was pointing at a cliff there. One team looked for several hours before they found it."
That's four transmitters in four states on one hunt! And remember, you East Coast dwellers, who can drive through five of your tiny states between breakfast and lunch, we're talking big states here. N6MI, holder of the old record, was the winner. His total of 460 odometer miles to find all four was lower than any of the five other teams.
 As hider for the mobile T-hunt of the 2002 ARRL Southwestern Division Convention in Escondido, California, Tom Sneden, then-KE6VCR and now K6VCR, transmitted through this 44-element 2-meter Yagi, 100 feet long. It was pointed at Mt. Palomar to create signal reflections that would confuse the hunters. [Tom Sneden, K6VCR, Photo] |
 Bob Miller, N6ZHZ, and Cathy Livoni, KD6CYG, are two of the most active ELT searchers in the Civil Air Patrol. For extra sensitivity in his RDF system, Bob uses this cubical quad with elements for 121.5 and 243 MHz. [Joe Moell, K0OV, Photo] |
Not Just Fun and Games
In a constant pursuit of new adventures, Southern California hams have held T-hunts on 50 MHz, 1.2 GHz and every band in between. However, 2 meters remains the most popular band. Most hunts, even the ones with several Ts, are on 146.565 MHz simplex, which is coordinated for T-hunting by the Two Meter Area Spectrum Management Association (TASMA). A typical T transmits from five to ten seconds at a time and then is silent for a minute or more.
T-hunters never seem to tire of their games of radio hide-and-seek. More importantly, they are ready with equipment and skills when called upon to quickly track down deliberate or inadvertent interference on the ham bands. Mike Obermeier, K6SNE, who was killed in the May accident, was one of the most active ARRL Official Observers in southern California. He solved or helped to solve dozens of stuck carriers, spurious signals and malicious interference cases, including the notorious Jack Gerritsen.
Mobile and on-foot foxhunting skills can be lifesaving. When an aircraft Emergency Locator Transmitter (ELT) starts squawking on 121.5 or 243 MHz in southern California, chances are the team of Bob Miller, N6ZHZ, and Cathy Livoni, KD6CYG, of Civil Air Patrol will be called out to find it. They credit their regular experiences on mobile T-hunts for their prowess at ELT tracking.
Mobile and on-foot transmitter hunting -- both are worth a try. You can read about the latest southern California hunting high jinks at the Southern California T-Hunters Web site, a project of Deryl Crawford, N6AIN, and Steve Heinemann, N6XFC.
The RDF Links page of my Homing In Web site lists URLs
and e-mail address for RDF contesting groups all over the USA. Perhaps there is one near you. If not, start one!
| Previous: ARRL First VP Chairs Global Amateur Radio Emergency Communications Conference | Next: Icom to be 2006 ARRL November Sweepstakes Principal Awards Sponsor |
