Technical Information

Receivers, headsets and a mapSome ARDF events may have receivers for you to borrow during the competition. While unfortunately there is no commercially produced ready made ARDF equipment sold in the UK, new or second-hand equipment can be obtained from continental Europe, Australia or Japan.

However, many competitors choose to build their own receiver. There is information on this page for those who would like to take up the challenge of building their own receiver, or who just want an idea of what would be involved in doing so.

Most ARDF competitors start out with a cheap and simple receiver and move up to a more sophisticated one once they have gained more experience in the sport.

Receiver resources

144 MHz Receivers

COMPACT 145/145E

This is a commercially available receiver from Jiri Marecek OK2BWN. More details here.

ROX-2

David Deane’s web site details the ROX-2T receiver using the classic TDA1083 ‘one-chip radio’, together with a novel way of controlling the receiver front-end gain. It achieves the low-cost/simplicity objective by single conversion to 10.7MHz. The web site gives further information for integrating the receiver with a “tape-beam” yagi antenna.

There are also references to other designs utilizing the  SA6xx family of surface mount IC designed for cellular radio. The RSSI output of the SA605/SA636 chip provides demodulated AM and DC drive for an audio S-meter using the VCO of the 4046 PLL IC.   More details here.

Junior 2

This design by Rainer Flosser DL5NBZ uses a BF961 dual gate MOSFET followed by a Siemens SO42P, a ZN414 am receiver chip and an LM386 audio amp. It is designed to be mounted at the feedpoint of the yagi antenna and has a balanced 75 ohm input for this reason. It is fitted in a 112x60x27 Eddystone diecast box. The ZN414 is now virtually unobtainable but the MK484 from Maplin is a reasonable equivalent. More details (in German) here.

ROF 1 from Norway

This receiver, in broad brush terms, is a ROX 2 with a PLL first LO to give accurate frequency setting. Full details are provided. More details here.

DF1FO advanced design

Nick Roethe has designed an advanced receiver based around a dual conversion arrangement reminiscent of the HPE2. It uses dual conversion at 10.7MHz and 455kHz with a phase locked loop for the first LO. Two dual gate mosfets are followed by a TCA440 for the IFs and an LM386 for the audio. The receiver uses a crystal filter, stores up to 4 frequencies and has an audio S meter. There is, of course, a digital display. The most innovative features are auto attenuation when the S meter hits FSD, range estimation, display of the remaining time that each transmitter is on the air and a low battery warning. There is a version that can be built into the boom of a yagi.  More details here.

3.5 MHz Receivers

Superfox 3.5GX

This is another commercial offering from Jiri Marecek OK2BWN. The design provides a narrow IF filter which significantly improves the sensitivity compared to receivers which use ceramic filters. More details here (pdf).

Junior 80

This direct conversion receiver uses a frame antenna in its original form. It comprises a BF254 RF stage, a diode mixer (pair BAT41), a BC549C and the ubiquitous LM386. The design is from Rainer Flosser DL5NBZ and it uses three RF transformers. More details (in German) here.

HRX80 from PA0HRX

This design by PA0HRX shows how the TCA440 IC can be used in a superhet scheme with very few extra components. It uses an LM386 as the audio stage. The selectivity is provided by ceramic filters (SFZ455A) with a bandwidth of 4kHz. Two ICs, two transistors and one coil (apart from the ferrite rod) are required for this simple but effective design. More details here.

HRX80 kit from G3ORY

These kits are no longer available due to difficulties with component sourcing. A re-design project is now in hand but will not result in a viable receiver until the end of 2013.

External links

International Amateur Radio Union (Region 1) ARDF page