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)

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Latest RDF News Headlines

2024 USA champsNow in the Homing In Championship ARDF News page:  Hungary will host the 2024 IARU Region 1 ARDF Champioships from August 9 - 14, 2024 near Pecs.  The First Individual Open ARDF Championships (IOAC) will also take place in parallel on the same courses and participants from USA and Canada are welcome.  Also, a young radio-orienteer from USA has competed in the 5th IARU World Youth ARDF Championships in Hungary, a ham from Boston is on his way to becoming an IARU ARDF International Class Referee, and two new kit products may soon provide an inexpensive way for local clubs and Scout organizations to bring ARDF to their communities.

2024 R-O champsCentral Michigan will be the site of our next national championships of on-foot transmitter hunting.  The 23rd USA Radio-Orienteering Championships and 11th IARU Region 2 ARDF Championships will take place October 9 - 13, 2024 in venues near Chelsea, MI.  A full week of activities is being planned, including two days of training and two days of practice, followed by competitions in sprint, foxoring and classics on two meters and eighty meters.  Meet Director will be Joseph Burkhead KE6MKR, a medal winner at the 2018 ARDF World Championships.  USA's championships are open to anyone of any age who can safely navigate in the woods with hand-held radio gear for several kilometers.  An Amateur Radio license is not a requirement.  Get more information here.

THRDFS cover Radio-OResults and photos of the annual "Antennas In The Park" transmitter hunt and barbecue at Hillcrest Park in Fullerton on May 4, 2024 and the on-foot two-meter transmitter hunting session and barbecue at Mission Bay in San Diego on May 18 are now in this site.  Upcoming southern California on-foot hunts will be announced here.  Many of these sessions feature workshops for building measuring-tape two-meter yagis and active attenuators as well as separate courses for beginners and advanced radio-orienteers.  For earliest notification of these events, you can join the southern California ARDF mailing list.

compassWant to find transmitter hunts taking place in your locality?  Long-time enthusiast Byon Garrabrant N6BG has begun publishing a list of regularly-scheduled hunts, both mobile and all-on-foot, at foxhuntlist.com.  He welcomes submissions from anywhere in the USA.  There is also a calendar of nationwide on-foot radio-orienteering sessions maintained by Backwoods Orienteering Klub.  This Homing In site will continue to post details of upcoming and past on-foot transmitter hunts in southern California (see next item).

CQ-WWFWThe 27th annual Worldwide Foxhunting Weekend (WW FW) was May 11-12, 2024 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.  After that, plan a mobile or on-foot hunt for a weekend in the near future.  This annual event is an ideal time for ham clubs and non-club groups around the country to enjoy this fast-growing sport.  For clubs that participated in this year's WW FW, the next thing to do (besides planning another hunt, of course) is to write up the results and submit with photos to your club's newsletter.  And when it's published, please send me a PDF or a link to the article.

Homing InMy latest (and probably last) Homing In magazine column is now in this site.  It's a detailed report on the 2023 World ARDF Championships in the Czech Republic plus the story of how John Abbott K6PFN of Los Angeles and his son brought ham radio foxhunting to a local scouting expo.  I submitted this column shortly after the championships concluded and it was scheduled for the November 2023 issue of CQ Magazine.  That issue has not yet been published and no information is available about when or if it will ever be published by CQ in any form, so I have released it here.

WC23 iconARDF Team USA competed at the 21st World ARDF Championships and brought home medals from the two-meter classic and foxoring events.  Classic, sprint and foxoring competitions took place August 27 through September 2, 2023 around the Technical University of Liberec in the Czech Republic.  The 2023 team was the largest to represent USA since radio-orienteers from our nation began attending these biennial world championships in 1998.  Team members were selected from the best performers at the USA ARDF Championships of 2022 and 2023.  Get many more details in this site.

2023 USA champsEastern Texas hosted the 22nd USA Radio-Orienteering Championships from April 19 - 23, 2023.  The site was Cooper Lake State Park near Sulfur Springs.  The schedule included a practice and training day followed by foxoring, sprint and classic events on eighty meters and two meters.  Participants ranged in age from nine to the seventies.  Some were first-timers eager to learn from the experienced ARDF experts.  There is a full report and links to the official results here.  Notice the new name for these championships.  There's more about that here.


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

Learn about international-rules on-foot hunting (ARDF, radio-orienteering) and how the sport is organized

Obtain RDF equipment for two-meter hunting on foot UPDATED

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

Buy or build a two-meter "fox" transmitter

Learn about 80-meter transmitter hunting

Top-Hit Transmitter Hunting Topics

USA ARDFMore and more hams and orienteers are discovering the fun of tracking down hidden transmitters out in the woods.  It's a worldwide sport with opportunities for friendly competition at home and abroad.  A ham radio license isn't a requirement, but it makes it lots more fun.  Learn the basics and get the international hunt rules at the "International Style Transmitter Hunting Comes to the Americas" page of this site.

AppsEasy-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 compilation of Homing In column reviews.

T-hunting vehicleMobile 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 "Let's Go T-hunting."

Ammo-can foxWhen 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.

Foxoring mapFor three decades, international-rules radio-orienteering competitions have had two classic 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.

Dual-polarization QuadFor 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."

DF2020TThe popular DF2020T Doppler RDF set by Global TSCM (and the MFJ-5005 clone) are sold out.  This nearly-plug-and-play RDF system has serial output for plotting bearings on PCs with GoogleHunt software by Bob Simmons WB6EYV.  For those who own one or are considering buying a used one, this page of the Homing In site has a product review plus antenna grounding improvements for early versions.

DFjrThe 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.

There are over 100 additional fact-filled pages in this site, including techniques, product information and build-it-yourself projects for radio direction finding.  For the complete Table of Contents and site search, click or scroll down.

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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 a year in CQ-Plus digital magazine.  After that, it appeared four times per year in CQ Amateur Radio 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.

Start of a mobile T-huntRadio 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 more information about mobile T-hunting.

Start of an on-foot hamfest huntMobile 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

Other resources

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.

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Joe MoellWho is KØOV? A registered professional electronic engineer and an active Amateur Radio enthusiast since age 11, Joe Moell KØOV has 55 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 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 almost 300 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 then 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.

Joe and April (WA6OPS) Moell are graduates of the University of Nebraska. They have served as organizers, course marshals and jurors at international-rules foxhunting championships.

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Surfing suggestion:  For a quick start into the world of mobile and on-foot hidden transmitter hunting, jump to Give Foxhunting a Try.

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 © 1996-2024 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 June 2024




Mobile T-Hunting | ARDF/Radio-O | CQWWFW | Local Events | Wildlife Tracking | Projects
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