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The Adcock antenna has been used for a long time for RDF. It is basically an interferometer.

All about radio direction finding (RDF)

Lots of projects and introductions to RDF and T Hunting

This low power transmitter is developed for ARDF exercising purposes but of course can be used as super QRP transmitter either. With 1 or 2 meter wire as antenna and a ARDF receiver with ferrite-rod antenna the range is about 100m but with better antennas and a 'real' receiver the range is probably much larger.

The website provides information on the Romanian Amateur Radio Federation's participation in the World Youth Radio Orienteering Championships in 2025. It includes details on the event, the participants, and their results.

For amateur radio operators engaged in **radio direction finding** (RDF) and **transmitter hunting** (T-hunting) activities, this resource provides a catalog of printed circuit boards (PCBs) for constructing various DF and foxhunt-related projects. The offerings include PCBs for 80-meter fox transmitters and receivers, UHF fox transmitters with audio recording capabilities, and several designs for general-purpose radio direction finders. Specific projects like the "Simple 80M ATX-80 Transmitter" and the "N0GSG DSP Radio Direction Finder" are listed, along with attenuator boxes and specialized components for Doppler DF systems. The catalog details PCBs for projects published in prominent amateur radio magazines such as *73's*, *CQ*, *QST*, and *PE*, indicating their origin and design pedigree. For instance, the "Montreal Fox Controller" is sourced from the *Homing-In* column by Joe Moell, K0OV. The resource also lists components for advanced Doppler DF systems, including main boards, LED display boards, and antenna switch boards, with options for programmed PIC microcontrollers. Pricing for each PCB is provided, allowing hams to acquire the necessary components for their DIY RDF endeavors.

Hidden transmitter hunting, often called fox hunting or Amateur Radio Direction Finding (_ARDF_), presents a unique challenge for radio amateurs. This resource details the _PicCon_ controller, a specialized device designed to automate the transmission of signals for such events. It integrates with a standard radio transceiver, functioning similarly to a packet radio TNC, by controlling the Push-To-Talk (PTT) line and injecting audio tones or modulated CW Morse code into the microphone input. The _PicCon_ unit is field-programmable using DTMF tones received via the radio, storing all settings in EEPROM for power-off retention. Its compact design and low power consumption (a few milliamps from a 7-35VDC source) make it suitable for remote deployment. An onboard LED indicates operational status, and a push-button allows manual start/stop of transmissions without DTMF. Typically supplied as a kit, _PicCon_ includes a PCB, components, and a comprehensive manual (available in HTML, RTF, and PDF formats). The kit provides a six-conductor interface cable, but users must supply radio and power plugs due to varied configurations. Byon, _N6BG_, developed this controller, which is available from the Byonics website.

Documentation to build your onw 80m ARDF receiver

The 80m TX described here is the well known ON7YD ATX-80 and timer, combined and re-engineered to fit a readily available enclosure by G3ZOI

Two-meter and aircraft band receiver specifically designed for RDF on foot, sold by Bryan Ackerly VK3YNG

This site serves a community of volunteer and paid professionals in Search & Rescue and Civil Air Patrol who save lives and Amateur Radio enthusiasts who use DF skills as a hobby. We provide antennas and other resources for people in these fields.

The RasHAWK team has used a Raspberry Pi as the basis for a networked RF sensor capable of supporting spectrum monitoring, signal intercept and direction finding (DF) operations.

Mobile and Fixed-Site Radio Direction Finders

The ÖVSV website provides extensive resources for Austrian radio amateurs, including details on its nine **Landesverbände** (regional sections) and the Austrian Military Radio Society (AMRS). It features information on licensing, legal frameworks, and **band plans** for both HF and VHF/UHF operations. The site also covers various amateur radio activities such as contests (HF, VHF/Microwave, Alpe-Adria, SOTA, ARDF), technical projects like WRAN, and educational content explaining what amateur radio is and how to become a licensed operator. Recent news items highlight events like the "Laa Funk '26" exhibition, the "OE5XLM" club station's participation in the CQ WW Contest, and the "International Marconi Day 2026" activation by "OE26M" from Küniglberg. The site lists upcoming events, including a 160m OE-Aktivitätsrunde, a seminar on Baluns/Ununs, and various club meetings and flea markets. Membership is facilitated through regional sections, and the site emphasizes amateur radio's role in independent communication during crises.

The 80 metre fox-or/test transmitter is a small low power transmitter which is designed to be used as an alignment aid for running up 80 metre foxhunt or ARDF receivers. It is also usable as a micro transmitter for fox-or-ing events.

Ardf holland, information about ardf activities in the netherlands, in english and dutch

An introduction to RDF contesting in southern California, updated from a paper originally submitted for Proceedings of the 1992 West Coast VHF/UHF Conference.

A 7 dB directional gain is reported for this portable VHF Yagi antenna design, which utilizes cut metal tape measure sections for its elements. The resource details the construction process for a 2-meter band antenna, emphasizing its ease of build and portability. It specifically mentions the design's suitability for radio direction finding (RDF), fox hunting, and communication with satellites and the International Space Station (ISS), highlighting its practical applications for amateur radio operators. The construction cost is estimated at under $20, with potential for even lower expense if salvaged materials like old tape measures and PVC pipes are used. The article references _Joe Leggio's_ (WB2HOL) original design, noting specific alterations made by the author. It also compares this design to other DIY Yagi antennas, including _FN64's_ 2-meter band and _manuka's_ 70-cm band tape measure Yagis, underscoring its unique combination of simplicity, portability, and effective performance with a 1:1 SWR achievable on the 2-meter band.

The Utah Amateur Radio Club - Radio Direction-Finding RDF

Since 2011, crkits offer radio kits that you cannot find on eBay or AliExpress. Includes HT-1A 20/40m Dual Band CW Transceiver Kit, D4D DSB Transceiver Kit for Digital Mode, R3500D ARDF Receiver, CW Transceiver Kit

Samples and documentation on RDF setups

ARDF IARU Region 1 working group

A home made RDF 3 elements Yagi that can be used for fox hunting. The particularity of this antenna is that it can be folded, in order to save space while travelling. In Dutch.

If your club holds only two-meter ARDF events, you are missing half the fun. There is another international foxhunting band, too.

Active RDF club in California

RDF Equipment Ideas for VHF Foxhunting and Radio-Orienteering. This information is primarily for the Amateur Radio two-meter band

This article details the design and construction of a homebrew two-element loop antenna array for HF reception. The DIY receiving antenna system consists of two 30-inch diamond-shaped loops spaced 20 feet apart, offering superior directivity compared to traditional vertical arrays. The design features broadband operation from 160m to 20m bands, requiring only phase-delay adjustments via feedline lengths. This home-built antenna system achieves 9dB RDF (Receiving Directivity Factor) performance comparable to a 300-foot Beverage antenna, while requiring minimal space and no ground radials, making it ideal for suburban installations and low-band reception.

The Peilgruppe Neandertal, featured on Peilsport.de, actively promotes _Amateur Radio Direction Finding_ (ARDF), also known as fox hunting. This German group combines radio technology with outdoor sport, participating in regional and national ARDF events. Members access current ARDF schedules, competition results, and downloadable certificates directly from the site. The content highlights the adventurous spirit of ARDF, emphasizing the blend of technical skill and nature exploration. DL7ET and DR9P are noted callsigns associated with the group, indicating active participation from experienced operators. The site also covers related activities like Foxoring, a variation of ARDF that integrates orienteering with radio direction finding. This resource serves as a central hub for the Neandertal group's activities, documenting their involvement in a sport that challenges both physical endurance and radio proficiency.

About Amateur Radio Direction Finding events, sprint and Fox-Oring spcialities. Sprints are intended to bring ARDF nearer to the public and to attract potential sponsors and new athletes to ARDF. Foxoring encourages ARDF enthusiasts to improve their orienteering skills.

The JUNIOR-2 presented here is a competition direction finder receiver that is easy to build and tune, but has all the features of the "big" receivers. It is especially suitable for beginners, young people or youth groups who have so far refrained from purchasing a 2m direction finder receiver for financial reasons.

Measuring the Frequency Accuracy and Stability of WWV and WWVH by Michael A. Lombardi. An examination of just how accurate these frequency standard stations are.

The RDF 10 second fold-out Yagi especially for fox hunting. have more fun stuff on this page. PD0G

Discover the best low band receive antennas for hams with limited space. Learn about the K9AY loop antenna and Shared Apex Loop Array, two alternatives to the traditional Beverage antenna. Understand the concept of Relative Directivity Factor (RDF) and compare the performance of different receive antennas. See how the Shared Apex Loop, patented by Mark Bauman (KB7GF), offers an RDF between 8 and 10dB. Find out how to optimize antenna performance and enhance your receive capabilities on 160, 80, and 40 meters. Explore the world of low band receive antennas with insights from WB5NHL Ham Radio.

Fox Hunting for Scouts. Jamboree can be an opportunity to promote ARDF among Scouts all around the world.