Homing In

The Art and Science of Radio Direction Finding (RDF)

Provided by Joe Moell, ham radio callsign KØOV. (That's K-zero-O-V)

Latest RDF News Headlines

Albuquerque Amateur Radio Club and New Mexico Orienteers hosted the 2011 USA ARDF Championships from September 14-18, 2011.  These annual national championships were combined with the biennial championships for International Amateur Radio Union (IARU) Region 2 (North and South America).  They were open to anyone of any radio-orienteering skill level, and were a chance to learn from experts.  There were separate days of competition on two meters and 80 meters, preceded by two days of optional intensive training.  The latest information, including links to results, is in this Homing In site. Over a hundred photos are now here, too.

The Fall 2011 issue of CQ VHF Magazine is now being distributed to subscriber mailboxes and ham radio stores.  In it, my Homing In column tells all about the 2011 USA and IARU ARDF Championships, held in Albuquerque in September..  Your local ham store may still have the Summer 2011 issue of CQ-VHF, in which my Homing In column reviews a new micro-transmitter from Byonics and some new plastic parts to improve your measuring-tape yagi from KI6DYX. There is also news from the Australian foxhunting championships.  I welcome your input for future articles, so please continue to send me your news of mobile and on-foot transmitter hunt activities.

The Tenth Friendship Radiosport Games (FRG) took place in Khabarovsk, Russia from August 13-16, 2011. There were competitions in on-air DX contesting, Morse code sending/receiving, and on-foot transmitter hunting under international rules (ARDF). Team USA, led by co-captains Dale and Kuon Hunt (WB6BYU and KB7WRG), took team silver in the ARDF event on two meters. Read more about FRG-2011 here.

Scouting's annual Jamboree-On-The-Air (JOTA) was October 15-16, 2011.  JOTA is an ideal time to introduce young people to all aspects of ham radio, especially hidden transmitter hunting.  Only the transmitter hider has to have a ham license!  If your club included transmitter hunting in JOTA, please e-mail me for possible use in an upcoming article.  For more information, see the Foxhunting for Scouts page at this site.

Want to see what you've been missing by not reading Homing In in CQ-VHF Magazine? Read this article from a recent issue, titled "Innovators in RDF: An Inventor, a Code Writer, and a Fox Meister." It tells about a pioneer in electronics and radio who may have patented the first switched-antenna RDF system, a new app for iPhone that triangulates RDF bearings, and the hams of Nashville who have fun with transmitter hunting and also have used it to help their community.

The fourteenth annual CQ Worldwide Foxhunting Weekend was May 14-15, 2011 but if your club didn't hold a hunt then, it's not too late! Start the fun now by reading the announcement at this site and my articles in the April and May 2011 issues of CQ Amateur Radio Magazine. The April article has the lastest ham radio foxhunting news, while the May issue has hunt stories and photos from 2010. After that, plan a hunt for a weekend in the near future, either in cars or on foot. For clubs that participated in Foxhunting Weekend 2011, the next thing to do (besides planning another hunt, of course) is send the results and photos to me for the follow-up article. Get the report form here.

Croatian Amateur Radio Association hosted the Fifteenth ARDF World Championships, September 13-18, 2010 and three Team USA members brought home medals. The headquarters site was in Opatija, a resort city on the Adriatic Sea. Team USA selections were made based on performance in the 2009 and 2010 USA ARDF Championships. Fourteen persons represented USA in the two-meter and 80-meter ARDF events and five others accompanied them to Croatia, including one who served as a member of the international jury. The First ARDF World Championships for the Blind were also held during the same week in Opatija with one person from USA in the competition.  Find out more about our medal winners and see two pages of photos starting here.

Quick Links to Information for Beginners
What Do You Want to Do?

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

Top-Hit Transmitter Hunting Topics

The Southern California T-Hunts for Beginners page has two monthly mobile hidden transmitter hunts in the Los Angeles and Orange County area where first-timers are especially welcomed and encouraged. There is also information about the always-on GeoHunt, a two-meter transmitter that you can hunt on your own at any hour of the day or night. 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 new Foxboxes for Mobile and On-foot Transmitter Hunts page in this site.

USA first attended the ARDF World Championships in 1998. The people we met and the lessons we learned helped set the foundation for our current success. Here is my classic article from CQ-VHF magazine about the first Team USA trip to Hungary. Learn how a Hungarian ham was instrumental in getting ARDF started in the Western Hemisphere. This ham became a world medal winner again in 2008.

For over ten 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," which is new to this site.

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 is also the title of my regular column on RDF that ran for 15 years in 73 Amateur Radio Today magazine and is now in CQ VHF 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 fifty 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?

Getting Started -- The basics

• Let's Go T-Hunting, an overview of how southern California hams organize their mobile hunts and the kinds of equipment they use. Put this article in your ham club's newsletter.

• Southern California T-Hunts for Beginners has details of two monthly mobile T-hunts in the Los Angeles and Orange County area where first-timers are especially welcomed and encouraged, plus some typical hunt photos.

• Frequently Asked Questions and answers about T-hunting and RDF from the Homing In mailbag. Topics include "fox" transmitters, dopplers, ELTs, covert and child tracking systems, "fingerprinting" and more.

• The CQ Worldwide Foxhunting Weekend is an annual event in the spring, sponsored by CQ Magazine.

• The new Radio-Orienteering Video by Gary Pearce KN4AQ would be a great program about on-foot foxhunting for your local radio club. It was made at the 2006 USA ARDF Championships. See the competitors in action and learn about how their RDF gear works.

RDF Topics in Print -- Read all about it

• TRANSMITTER HUNTING---Radio Direction Finding Simplified (THRDFS) by Moell and Curlee, a comprehensive illustrated text on all aspects of RDF including theory, techniques, and projects for the HF, VHF, and UHF bands. You can get it by check or with your credit card using PayPal.

• Sneak peek at the latest Homing In columns in CQ VHF Magazine and other current KØOV articles.

• Homing In Article Index, with topics for all of the regular columns since 1988 plus other KØOV magazine features (over 250 total).

• Foxboxes for Mobile and On-foot Transmitter Hunts, what to buy or build.

• Complete plans for KØOV's Wide-Range Doppler Antenna Array with improved sensitivity and bandwidth. Works with the Roanoke Doppler and other dopplers too!

• Complete plans for KØOV's simple Offset Attenuator for ARDF.

• Theory and construction of KØOV's Multiple-polarization Quad for mobile T-hunting.

• Complete plans for a Doppler-to-APRS interface by Robert Swain. Also see this parts availability update

• Parts and Hardware Sources for RDF home experimenters and builders, including RF attenuators, polar bearing plots, circuit boards for the Roanoke Doppler, and PIN diode suppliers.

Commercial RDF Equipment -- Getting the most from it

• Design improvements for the HANDI-Finder and other "bow-tie" RDF sets. Teach yours to know front from back.

• Design improvements for the Ramsey Foxhound and SlyFox.

• Design improvements for the Dick Smith K-6345 Doppler set.

• Documentation and design improvements for the Agrelo DFjr Doppler set.

Follow-up and Support -- for readers of THRDFS and Homing In

• Updates to THRDFS since publication, new addresses/phones, parts substitutions, etc.

• Reports from builders about third-party Roanoke Doppler circuit boards.

• More on the KØOV Shrunken Quad, parts and construction hints for this popular THRDFS project.

• More on the KØOV NorthScope (July, August and September 1997 columns), including a circuit analysis plot and HVPS schematic, plus resources for fluxgate compasses and analog multipliers.

• More on the VE2JX/VE2EMM Montreal Fox Controller. Source and object code downloads, circuit board information and useful links for this project by VE2JX and VE2EMM in Homing In for April 1998.

Championship Radiosports -- Taking on the world

• International-Style Transmitter Hunting Comes To The Americas. The basics of international-rules on-foot foxhunting and the history of its development on our continent.

• Championship Foxhunting News from around the world. Results of recent international competitions and announcements of upcoming ones.

• Equipment Ideas for Radio-Orienteering. Inexpensive transmitting and receiving gear for international-style ARDF.

• Electronic Scoring for ARDF, what it is, how it works, and why more and more local events and championships and are using it.

• Try ARDF on 80 Meters. If your club does radio-orienteering only on two meters, you're missing half the fun. There's another international foxhunting band, too.

• Foxhunting for Scouts, how to introduce youngsters to RDF and foxhunting at the Jamboree-On-The-Air and other Scouting events.

• Extenders Aid Handicapped Foxhunters, a novel way to include persons with disabilities in on-foot foxhunts.

• Tips for Hosting ARDF Championship Events, to bring the best foxhunters to your home town.

• Jay Thompson W6JAY, a young medal-winning radio-orienteer from Santa Ana, California who has been honored by ARRL and Amateur Radio Newsline.®

• Current events in southern California -- Results of 2011 sessions as well as announcements of upcoming ones.

• 2011 USA and IARU Region 2 Championships -- Back to Albuquerque for another well-organized event in forests that had not been used before. In this site are the story and five pages of pictures.

• Year 2010 events -- Southern California ARDF sessions in Irwindale, San Luis Obispo, Rowland Heights, Los Angeles, Mt. Laguna, Mt. Pinos and Placentia

• 2010 IARU ARDF World Championships -- Team USA brought back three more medals from this event near on the Adriatic seacoast.

• 2010 USA National Championships -- Soggy running through the forest and skipping through a creek in western Ohio. In this site are complete results and five pages of pictures.

• Year 2009 events -- Southern California ARDF sessions in San Dimas, Topanga, Placentia, Rowland Heights, Fullerton, Irwindale and Goleta.

• 2009 USA National Championships -- Our first national championships to be on the east coast brought out the largest number of competitors so far. In this site are complete results and five pages of pictures.

• Year 2008 events -- Southern California ARDF sessions in Fullerton, Rowland Heights, Placentia, Long Beach, San Dimas, Mt. Pinos, Huntington Beach and San Diego.

• 2008 IARU ARDF World Championships -- Team USA brought back another medal from this event near Seoul, Korea.

• 2008 USA National Championships -- Texas hams put on well-planned and well-executed comptitions in a pine forest near Austin. In this site are complete results and dozens of pictures.

• Year 2007 events -- Southern California ARDF sessions in Fullerton, Los Angeles, Placentia, Long Beach, Brea, Goleta, Topanga, San Pedro and San Dimas.

• 2007 USA National Championships -- A June wildfire didn't keep radio-orienteers from ending their summer by tracking transmitters in the Sierras of California. This site has complete results and dozens of action photos.

• Year 2006 events -- Southern California ARDF sessions in Rancho Santa Margarita, Topanga, Goleta, Placentia, Long Beach, San Dimas and Huntington Beach.

• 2006 IARU ARDF World Championships -- USA took home its first World Championships medal from this event on the Black Sea coast of Bulgaria.

• 2006 USA National Championships -- A beautiful North Carolina forest was filled with radio-orienteers on an April weekend. This site has a wrap-up report and dozens of photos.

• Year 2005 events -- Southern California ARDF sessions in Rowland Heights, Rancho Santa Margarita, Los Angeles, San Dimas, Placentia, Huntington Beach, Goleta, Glendora and Agua Dulce.

• 2005 USA National Championships -- Albuquerque hams surpassed their 2001 hospitality as they put on this event, which was combined with the Third IARU Region 2 Championships. This site has the results and dozens of photos.

• Year 2004 events -- Southern California ARDF sessions in Los Angeles, Fountain Valley, Rancho Santa Margarita, Placentia, San Dimas, and Fullerton.

• 2004 IARU ARDF World Championships -- A 21-member delegation from USA went to Czech Republic to compete and be part of the international jury.

• 2004 USA National Championships -- A 2m hunt in a boulder-filled desert park and an 80m hunt at 8000' in the mountains were the main events of these championships in California. This site has a complete wrap-up including the medal winners, plus an album of 40 photos and a first-person account from a first-time medal winner.

• Year 2003 events -- Southern California ARDF sessions in Los Angeles, Fullerton, Placentia, Goleta, and Anaheim.

• Hamcon/Foxhunt-2003 -- Another great ROCA in San Pedro, California, with lots of transmitters and prizes.

• 2003 USA National Championships -- Over forty radio-orienteers converged on Oxford, Ohio in late July for training and foxhunting fun. This site has the results and an album of 60 photos.

• Year 2002 events -- Southern California ARDF sessions in Fullerton, Fountain Valley, Long Beach, Huntington Beach and Thousand Oaks.

• 2002 IARU ARDF World Championships -- Team USA performed better than ever before at this premier event in Slovakia. This site has USA's results and first-person accounts.

• 2002 USA National Championships -- Over two dozen stateside foxhunters braved difficult courses to win medals near beautiful Pine Mountain, GA. This site has the results and an album of 40 photos.

• Year 2001 events -- Southern California ARDF sessions in Fullerton (2), Rowland Heights, Huntington Beach and Placentia.

• 2001 USA National Championships -- Ten states and three foreign countries were represented at this historic event in Albuquerque, NM.

• Year 2000 events -- Southern California ARDF sessions in Fullerton, Fountain Valley, Pasadena, Huntington Beach and Placentia (2).

• 2000 IARU ARDF World Championships -- A dozen foxhunters from six states made the trip to Nanjing, China to compete against the best.

• Team USA 2000 Qualifying Runs -- A difficult 2-meter hunt on a hot day, plus California's first 80-meter ARDF event.

• Hamcon/Foxhunt-1999 -- Southern California's first ROCA, 20 foxes to find, prizes for everyone.

• 1999 IARU Region 2 ARDF Championships in Portland, Oregon -- Eight states and seven other countries were represented. This site has the results and an album of 47 photos.

• Schabarum Park 1999 -- Preparing Team USA for championships in Portland.

• Antennas In The Park 1999 -- Informal, but so much fun that it has become an annual tradition.

• 1998 IARU ARDF World Championships -- In Nyiregyhaza, Hungary. This was USA's first time to take on the radio-orienteers of the world.

• Schabarum Park 1998 -- Preparing Team USA for championships in Hungary.

• West Coast VHF Conference 1996 -- 1995 was so much fun that we had another one.

• Hamcon/Foxhunt-1995 -- Southern California's first big international-style foxhunt.

• Friendship Radiosport Games 1991 -- The first international-rules ARDF event in the USA.

Volunteer Opportunities -- Use your RDF skills to help researchers and protect wildlife

• The Volunteer Wildlife Tracking News page, where you can find out about current opportunities to serve.

• The Burrowing Owl Project History page, detailing how volunteers in southern and western states have helped researchers in the provice of Saskatchewan and the state of Washington since 1998.

• The Indiana Bat monitoring/tracking project in New York state.

• The Northern Saw-whet Owl monitoring project in Pennsylvania and eastern states.

• Frequently Asked Questions About Wildlife Tracking, including equipment and antenna suggestions.

• Was That Really A Wildlife Tag? describes squegging oscillators and their unique charactertistics.

Other resources

• A tribute and memorial information for Mike Obermeier K6SNE and David Gordon-Ross N6IDF, who died accidentally on May 27, 2006 during a "Mini All Day" mobile T-hunt.

• Over 280 RDF-related links and Homing In Correspondents to help you find T-hunts and ARDF events in your own area. Equipment sources, too.

• Where to find RDF-related mailing lists (reflectors), to bring transmitter hunting news directly to your electronic mailbox.

• Search this site by word, name, callsign or phrase.

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 over 40 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 230 published articles on the subject, including his monthly Homing In columns that ran for 15 years in 73 Magazine and now appear in the quarterly CQ VHF Magazine. As a Technical Advisor to ARRL Headquarters, he authored a new 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.

Joe and April (WA6OPS) Moell are graduates of the University of Nebraska. They have served as Course Marshals and Jurors at international foxhunting championships. When not participating in transmitter hunts or writing about it, they teach ham radio licensing courses and help support the emergency communications needs of the hospitals in their county.

Having problems browsing here? No pages are "under construction," but linking errors and server glitches can occur. If you get an error message when attempting to link to a page at this site, please send e-mail to me, stating which page you could not access. Also please report any stale links you encounter or any problems in displaying these pages. They are designed to look good and load rapidly on any browser version and at any screen resolution. They're printer-friendly, too. No annoying frames, fancy backgrounds, pop-up windows, animations, Google ads, background music, tickers, sponsored links, cookies, third-party banners or LIKE buttons here --- just an abundance of original and useful information, suitable for all ages. My privacy policy is very simple: I don't collect any identifiable information about you when you surf here. If you send me an e-mail inquiry or buy a book, I won't give your e-mail address or other information to anyone else without your permission.

Amateur Radio operators bring joy to hospitalized children every year during the holiday season.  Find out how by visiting the North Pole Network (NPN) Web site.  NPN has been a tradition in Orange County, California since 1976.  The 2011 North Pole Network report is now online.

Although not about RDF, another great ham place to browse is the Hospital Disaster Support Communications System (HDSCS) site. There you will learn how volunteer Amateur Radio operators can be an important backup communications resource for hospitals, if the hams are well organized and trained. The eighty members of the HDSCS in Orange County, California have served over 30 hospitals in over 110 communications emergencies during the past 30 years. We have rapidly responded following earthquakes, wildfires, floods, power outages and internal switchboard failures. If you think that your local ARES® or RACES group is presently serving all of the disaster communications needs of your community, you may consider taking on a new mission after seeing this site.

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 © 2011 Joseph D. Moell. Text, photos and original graphics may not be served or reproduced elsewhere without permission.

Contact info:
Joe Moell
PO Box 2508
Fullerton, CA 92837
k0ov@homingin.com

This page updated 1 January 2012