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After a hiatus of over a year, on-foot transmitter hunting activities are coming back. Southern California's first on-foot radio foxhunting session since 2019 is being planned for Saturday, May 8, 2021 at Hillcrest Park in Fullerton as part of the Fullerton Radio Club's usually-annual Antennas In The Park event to celebrate the CQ Worldwide Foxhunting Weekend. There will be two-meter and 80-meter transmitters to find, plus a workshop for building measuring-tape yagis and active attenuators. (Click for details, directions and times). For earliest notification of these events, you can join the southern California ARDF mailing list. Radio-orienteering sessions are also taking place in North Carolina and in the Cincinnati area. There is a calendar of upcoming ARDF sessions all over the USA. This Homing In site also has results and photos of previous southern California radio-orienteering events.
Have you tried transmitter hunting on the six-meter band? A group of hams in the Riverside, California area holds Saturday morning mobile hunts on 50.3 MHz FM simplex, usually twice a year. The next hunt will be April 24, 2021. Bring your hunting gear and be at the hilltop home of Will Anderson AA6DD before the transmitter goes on at 9:30 AM. This is intended to be an easy hunt with the hiders waiting for you to find them in a park within a 15-mile radius. Most hunters will be using simple loop antennas. Download a flyer with address and other details. More information on six-meter RDF and results of previous hunts are now in this site.
The 24th annual CQ Worldwide Foxhunting Weekend will be May 8-9, 2021. The CQWWFW is an ideal time for ham clubs and non-club groups around the country to enjoy this fast-growing sport. Although large gatherings in local parks for on-foot transmitter hunting may be contrary to "safer-at-home" regulations for unvaccinated persons, there are many ham groups around the country that are enjoying in-vehicle hidden transmitter hunts, following appropriate social distancing and related precautions. For more on Foxhunting Weekend, read the announcement at this site and my column in the February 2021 issue of CQ Magazine.
The February 2021 issue of CQ Amateur Radio Magazine is now online and coming to print subscribers. In it, my Homing In column visits the Naval Air Warfare Center, Weapons Division at Pt. Mugu, California, where long-time foxhunter Norm Goodkin K6YXH taught RF principles using ham radio foxhunting. Norm also spins tales of southern California mobile T-hunts going back to his high-school days. Some ham radio stores may also have the November 2020 issue, in which my column tells why yagis and quads are the RDF antennas of choice for southern California two-meter mobile transmitter hunters and shows some simple ways to mount these rotating antennas on your vehicle. My column on radio direction finding appears in CQ Magazine at least four times per year. CQ Magazine is available by subscription and printed issues are sold in Amateur Radio stores. CQ is also available by subscription in digital form, viewable on PC, Mac, iPad, iPhone and Android. I welcome your input for future articles and columns, so please continue to send me your news of mobile and on-foot transmitter hunt activities.
The twentieth USA ARDF Championships have been rescheduled and relocated. Anticipating that vaccines will alleviate the COVID threat by fall, the ARRL ARDF Committee has selected the forests of North Carolina for this year's national championships. Dates are October 14 - 17, 2021 and the sponsoring organization will be Backwoods Orienteering Klub. There will be classic five-fox courses on two meters and eighty meters plus sprints and foxoring events. USA's Championships are open to anyone at any skill level, with or without a ham radio license. Medal winners may be selected for positions on USA's team to future ARDF World Championships. Visiting competitors from outside USA are welcome. Get more details here.
Amateur Radio Union of Serbia (SRS) will host the Twentieth ARDF World Championships, August 29 through September 4, 2021. The site will be the resort of Zlatibor, Serbia, about 230 km from Belgrade. At least 30 countries are expected to participate, including USA. These championships were scheduled to take place in 2020 but were postponed for one year due to COVID-19. All 2021 regional championships that were to be in 2021 will take place in 2022, and so forth. World Championshps feature formal competitions on two meters and 80 meters, plus sprints and foxoring. Each country may have up to three persons per age/gender category on its team. Team USA positions are filled based on performance in recent ARDF events, but there is usually room for inexperienced foxhunters in some categories. Get the details here.
Easy-to-use apps for Apple and Android tablets and phones can simplify bearing plotting and triangulation over short and long distances. They are useful for both on-foot and mobile transmitter hunting. Bearings can be entered manually or with the internal device compass. Some apps allow entering bearings taken by other hunters or networing with them during the hunt. One new app has an RS-232 interface to Doppler RDF sets. Read all about Foxhunt Pro, SigTrax Plus and Map-n-Compass apps in this updated compilation of Homing In columns.
Obtain RDF equipment for two-meter hunting on foot
Attend a southern California on-foot transmitter hunt
Participate in national and world championship hunts
Learn about mobile transmitter hunting (T-Hunting) and the equipment that hunters use
Attend a southern California two-meter mobile T-hunt
Buy or build a two-meter "fox" transmitter
Learn about 80-meter transmitter hunting
The Southern California T-Hunts for Beginners page has has information about three monthly mobile hidden transmitter hunts in the Orange County area where first-timers are especially welcomed and encouraged. On two of them, there are usually some clues to help everyone eventually find the transmitter and on one, you can compare bearings with other hunters on a separate frequency. Mount some RDF gear on your vehicle and come on out!
Mobile hidden transmitter hunters have regularly prowled the streets in search of the elusive sources of unusual signals for more than four decades. Equipment has evolved, but the adventure and intrigue remain the same. Read "T-Hunting Then and Now -- From Gooney Birds to GPS" in this site for stories of classic mobile T-hunts in the Los Angeles area. Some of them, but not all, could be done again today. Then to find out what it's like nowadays, and to help get your club started in this activity, read "Transmitter Hunting, Southern California Style."
When it's your turn to hide the transmitter, what will you use? It depends on the range and duration of the hunt, as well as whether or not the transmitter must be unattended and automatic. It's important to match your foxbox and its location to the level of proficiency of the hunters. There are many options, and you can read about them in the Foxboxes for Mobile and On-foot Transmitter Hunts page in this site.
For three decades, international-rules radio-orienteering competitions have had two major competition days. Each participant must compete on the two-meter band and the 80-meter band. The 2012 USA and World ARDF Championships included competitions in two new events: sprints and foxoring. The sprint is a shortened form of the five-fox 80-meter ARDF run that's intended to be a demonstration for the public. Foxoring is a combination of classic orienteering and direction-finding on 80 meters. More information about these new events can be found here.
For over twenty years, I have used a special cubical quad for mobile transmitter hunting on two meters. From inside the vehicle, I can select the signal polarization. Find out why this is important, why I like this antenna and how to make one for yourself in a classic Homing In column titled "Build a Multiple-Polarization Quad."
The Agrelo DFjr Doppler RDF set has been out of production for over ten years, but there is still a great deal of interest in it. DFjr was the first inexpensive plug-and-play Doppler set designed for interface to computer mapping systems and APRS. For those who own one or are considering buying a used one, the DFjr page on this site has a downloadable manual, my 73 Magazine review, antenna system improvements, and frequently asked questions about this product.
What's "Homing In?"
Homing In refers to the process of tracking down the source of a radio or other electromagnetic signal using radio direction finding (RDF) equipment.
Homing In is also the title of my regular column on RDF that ran for 15 years in 73 Amateur Radio Today magazine, then for ten years in CQ-VHF magazine and now appears quarterly in CQ-Plus digital magazine. At this Homing In site, you will find more about these columns, plus RDF articles that I have written for other publications, including Monitoring Times, CQ VHF and QST magazines. There is also information about my comprehensive book on the subject.
Radio direction finding is used to find sources of interference to any form of wireless electronic communications, including broadcast and two-way radio, television, and telephones. It is also used to track missing or stolen cars and other property. Search and rescue workers use it to find persons in distress. Emergency Locator Transmitters in downed aircraft are tracked with RDF techniques.
Most of the information at this site pertains to RDF equipment and techniques for Amateur Radio (ham) operators. Hams use RDF to track jamming stations and stolen equipment, but more often, they use it just for fun. Hidden transmitter hunting has been done by hams for about seventy years and it is a growing activity. T-hunting refers specifically to hunts involving hams driving in RDF-equipped vehicles. A mobile T-hunt is best described as hide-and-seek for all ages with radio gear. When you set out on a T-hunt, you never know where you'll end up, and you have no idea what you're going to find. No form of ham radio contesting is more fun! Mobile T-hunting is done in cities and towns all over the USA, and elsewhere in the world. Depending on the frequency band and the nature of the hunt, the hunters use loop, yagi, quad, doppler and time-difference-of-arrival RDF antenna systems mounted on their vehicles. Click here for for general information about mobile T-hunting or click here for beginner-level T-hunts in southern California.
Mobile T-hunting is called foxhunting in some parts of the USA, but everywhere else in the world, the terms "foxhunting" and ARDF refer to another kind of RDF contest, done completely on foot in large woods and parks. It's a map-and-compass sport similar to orienteering, with about a half-dozen "fox" transmitters to find in a period of two hours or so. Someday this sport, which is also called foxtailing, fox-teering and radio-orienteering, may become an Olympic event. Meanwhile, it's a fun-filled activity for your hamfests and Scout Jamborees. Try it, and you may find yourself at the next annual national USA ARDF Championships. You might even become a member of ARDF Team USA, which has competed in five foxhunting World Championships. Click here for for general information about radio-orienteering or click here for beginner-level ARDF events in southern California.
Keep reading---you will find lots more about foxhunting, T-hunting, and other uses of RDF at this site.
What's at the Homing In Site?
Find your topic of interest below in the complete Table of Contents (or as some call it, the Site Map). Or you can Click here for the Site Search page.
Getting Started -- The basics
RDF Topics in Print -- Read all about it
Home-built RDF Projects -- Inexpensive and educational
Commercial RDF Equipment -- Getting the most from it
Follow-up and Support -- for readers of THRDFS and Homing In
Championship Radiosports -- Taking on the world
Results, stories and photos of ARDF sessions, large and small
Volunteer Opportunities -- Use your RDF skills to help researchers and protect wildlife
Spending a few minutes at this Homing In site will give you a jump-start into the world of transmitter hunting. After that, you can find out how to get involved in mobile T-hunts in your area by visiting local T-hunt/foxhunt web sites and contacting nearby Homing In Correspondents listed on the links page. You'll find manufacturers and suppliers of RDF gear there, too.
Who is KØOV?A registered professional electronic engineer and an active Amateur Radio enthusiast since age 11, Joe Moell KØOV has 50 years of experience designing radio-frequency circuits and systems for broadcast, communications, and radar, ranging from near-DC through microwave frequencies. He has designed new devices for radio direction finding and has written about RDF and other topics for almost every ham radio publication in the USA. In February 1998, he was appointed by the American Radio Relay League (ARRL) as the USA's first ARDF Coordinator, to promote international-style foxhunting and to organize Team USA for international ARDF competitions. He also conducts the annual CQ Worldwide Foxhunting Weekend.
Joe collaborated with Tom Curlee WB6UZZ to write TRANSMITTER HUNTING---Radio Direction Finding Simplified, a comprehensive text on RDF, and has written over 280 published articles on the subject, including his monthly Homing In columns that ran for 15 years in 73 Amateur Radio Today magazine, then for ten years in CQ-VHF magazine, for one year in CQ-Plus digital magazine and now appears four times per year in CQ Magazine. As a Technical Advisor to ARRL Headquarters, he authored a chapter on RDF for The ARRL Handbook and has made more than 100 presentations on transmitter hunting to clubs, conventions, classes and seminars. As time permits, he is available for private engineering consulting.
Surfing suggestion: For a quick start into the world of RDF and mobile hidden transmitter hunting, jump to Let's Go T-Hunting.
Please note that this Web site is built and maintained independently by Joe Moell. It is not sponsored by or affiliated with CQ Publications, 73 Amateur Radio Today, Wayne Green Enterprises, TAB/McGraw-Hill, ARRL, or any other commercial or non-commercial entity. All content is protected by applicable intellectual property laws.
Entire site Copyright © 1996-2020 Joseph D. Moell. Text, photos and original graphics may not be served or reproduced elsewhere without permission.
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This page updated 15 April 2021