DL3BC

Since I am a little restricted in building antennas at my home I am always looking for amateur radio outdoor activities. Besides SOTA ARDF is such a wonderful activity which has the side effect of sportive training!

The logo of the ARDF department of DARC

What is ARDF?
ARDF means Amateur Radio Direction Finding. It is also often called "fox hunting" or "radio orienteering".
In short you have to find usually 5 transmitters (the "foxes") hidden in the landscape by bearing their directions.
The transmitters work time controlled. Every single one transmitts its identifier in Morse codeoften called "CW" for one minute and then the next one starts its transmission. The identifiers for the transmitters are:
1st transmitter: MOE
2nd transmitter: MOI
3rd transmitter: MOS
4th transmitter: MOH
5th transmitter: MO5
This seems to be confusing if you do not know Morse code. But it is simple when you hear it because the always identical beginning (Morse code - -   - - - for "MO") is followed by the a number of dots representing the transmitter number.
Examples:
- -   - - -   . .    stands for MOI, number 2
- -   - - -   . . .  stands for MOS, number 3
Here you can find sample sound files (-> scroll down to "Hörproben...").
When you found a transmitter you put a stamp on a card in order to verify that you really found it.
The number of found transmitters and the time you needed therefor determines the ranking. The faster you are the better the ranking, but the number of found transmitters is more important than the time. That means if you found all transmitters in a longer time than another one who found only a part of the transmitters you will win.
Since the experienced participants usually find all transmitters for them mainly the time determines their ranking.

Frequencies used for ARDF
Mainly two amateur radio bands are used for ARDF:
the 80 meters band (3.5 MHz) and the two meters band (144 MHz).
The advantage of the 80m band (shortwave band) is that there are not so much reflections resulting from buildings, mountains, trees etc. than on the 2m band. This is due to the wavelegth. These reflections influence the bearings often very much. You think you hear the transmitter e.g. from North, but it is in West direction and in the North there is only a hill which reflects its waves.
That's why the 80m band is the preferred one for beginners to get some experience.

What do you need for ARDF?
First of all you need a bearing receiver. Usually special portable receivers are used for ARDF because regular amateur radio receivers are too big and/or too heavy.
80m ARDF receivers have a build in antenna. Mostly a ferrite antenna. Sometimes you find also magnetic loop antennas.
The receiver itself can be a relative simple one. Often direct mixers are used. You can find a lot of descriptions in the web (e.g. on DXzone.com, my one is described here ). As far as I know there are no commercial ARDF receivers available on the market.
Very often you can loan a receiver from the organiser of the ARDF competition if you do not own one.

My 80m ARDF receiver 

2m ARDF receivers often use HB9CV or 2 or 3 element Yagi antennas which are mechanically fixed to the receiver.

My 2m ARDF receiver

Furthermore a compass would be very helpful for orientating oneself with the help of a map provided by the organiser. I constructed a special board for holding the compass and the map. During the fox hunt I orientate it to the North according to the compass and draw my bearings. 

My map and compass holder

Did I awake your interest?
Fox hunting is really fun! You do not need an amateur radio licence for it! Contact your local amateur radio club or search the web for ARDF competitions in your neighbourhood. As already mentioned very often you get a receiver on loan if you do not own one and sometimes there are short seminars for beginners.

A good introduction is available as PDF file from the ARDF department of the DARC (in German language): -> click here and scroll down to "Seminarunterlagen" -> "Einführung in das Amateurfunkpeilen" 

You can learn the rules and train your tactics also without running - from your PC with the little program "foxhunter" written by Günther Fromhagen, DK8OH, which you can download from here .

If you want to learn about ARDF in theory before you start the first time I also can recommend the book "Handbuch Amateurfunkpeilen" by Peter Gierlach, DF3KT, published in the DARC-Verlag (in German language!).

Web links

ARDF and Orienteering by DF3KT
Information and dates for ARDF and (the related sport) Orienteering

ARDF department of the German Amateur Radio Club
Information, dates, forum, technics, ...

IARU Region 1 ARDF Working Group
Information and the official championship rules

A nice video about ARDF on YouTube by KN4AQ