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

OH-KY-INRegistration is now open for the 2017 USA ARDF Championships, which will also be the ARDF Championships of IARU Region 2.  Optional training days will begin on July 31, followed by foxoring, sprints and classic orienteering events that will conclude on August 6.  Make plans now to attend and compete in the beautiful forests of the Cincinnati area.  The events are open to anyone, with or without an Amateur Radio license.  Get more information here.

Radio-OIt has been a very rainy winter here in southern California, so we have not scheduled any on-foot transmitter hunting sessions for a while.  But we are planning now for a warm, dry spring.  On May 6, 2017 there will be an ARDF session in the San Diego area.  Download an information flyer.  On Saturday, May 13, 2017 the annual Antennas In The Park transmitter hunt and barbecue will take place at Hillcrest Park in Fullerton.  (Click for Fullerton directions and times.)  Then on Saturday, May 20 will be the annual ARDF and antenna building session on the campus of Cal Poly University in San Luis Obispo.  (Click for Cal Poly directions and times.)  For earliest notification of these events, you can join the southern California ARDF mailing list.  If you live elsewhere, click to get contacts for other North America ARDF sessions.  This Homing In site also has results and photos of previous southern California radio-orienteering events, including Lake Los Carneros on November 12, 2016.

THRDFS cover JOTAThe 2017 update of Scouting's Radio Merit Badge includes an option for Amateur Radio Direction Finding activities.  Now Scouts and their leaders can experience on-foot hidden transmitter hunting as part of their introduction to the world of Amateur Radio.  Read about how you can help your local radio club bring foxhunting fun to Scouts in your community.

CQThe April 2017 issue of CQ Amateur Radio Magazine is being distributed to subscribers and Amateur Radio stores.  In it, you can read my article about the upcoming CQ Worldwide Foxhunting Weekend.  Some ham radio stores may still have the February 2017 issue of CQ Magazine, in which my my Homing In column tells all about the on-foot and vehicular fun across the country and elsewhere in the world during the 2016 CQ Worldwide Foxhunting Weekend.  My column in the November 2016 issue is a full report on ARDF Team USA's experiences in Bulgaria during the 2016 ARDF World Championships.  This column on radio direction finding now appears in CQ Magazine at least four times per year.  CQ Magazine is available in print by subscription and in Amateur Radio stores.  You can also subscribe to CQ 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.

BulgariaARDF Team USA 2016 has won seven medals in Bulgaria.  The Bulgarian Federation of Radio Amateurs (BFRA) hosted the Eighteenth ARDF World Championships for national teams September 3 through 9, 2016.  The World Championships were preceded by the ARDF World Cup for individuals August 29 through September 2.  The site was Albena on the Black Sea coast of Bulgaria.  At least 39 countries participated, including USA.  Formal competitions took place on two meters and 80 meters, plus sprints and foxoring.  Each country was permitted to have up to three persons per age/gender category on its team.  Team USA positions were filled based on performance in recent ARDF events.  USA medalled on each day of World Cup competition and also earned medals during the World Championships.  Read the latest on ARDF Team USA's participation here.  Two pages of photos have just been posted.

CQ-WWFWStart making plans for your participation in the nineteenth CQ Worldwide Foxhunting Weekend (CQ WW FW), May 13-14, 2017.  This annual event is an ideal time for ham clubs and non-club groups around the country to enjoy this fast-growing sport.  Read the announcement at this site and my articles in the February and April 2017 issues of CQ Magazine.  Whether you choose mobile T-hunting or on-foot radio-orienteering, be sure to get out of the shack and have an outdoor adventure during the CQ WW FW.

CQ cover Texas ARDFKilleen, Texas was the site of the 2016 USA ARDF Championships.  Texas ARDF group and the Austin Orienteering Club staged classic competitions on two meters and 80 meters, plus sprints, foxhunting and optional practice courses from April 6 through 10.  Most events were at the Parrie Haynes Youth Ranch and Equestrian Center, with over 2000 acres of equestrian trails and facilities for other outdoor sports.  USA's ARDF Championships are open to all.  Visiting competitors from outside USA are welcome.  Some of USA's medal winners are being invited to compete on Team USA at the ARDF World Championships in Bulgaria next September.  Lots of photos and complete results are available.  Learn more here.

AppsNew 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.  Read all about Foxhunt Pro, SigTrax and Map-n-Compass apps in this sample Homing In column.

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

CQ Mag April 2009 Learn about international-rules on-foot hunting (ARDF, radio-orienteering)

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 UPDATED

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.

FRCThe 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!

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 "Transmitter Hunting, Southern California Style."

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 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.

Dual-polarization QuadFor 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."

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 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.

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 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.

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 over 45 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 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 hear in CQ 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.

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G-RatedHaving 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 on my pages --- 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.

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 34 hospitals in over 120 communications emergencies during the past 36 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 © 1996-2016 Joseph D. Moell. Text, photos and original graphics may not be served or reproduced elsewhere without permission.

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Joe Moell
PO Box 2508
Fullerton, CA 92837


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This page updated 6 April 2017  





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