Auckland Branch 02

New Zealand Association of Radio Transmitters (Inc.)


Fox Hunt

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Fox Hunting

ARDF - Amateur Radio Direction Finding using 80m gear

  • The instructions are also provided in a Word Document for your convenience
  • Three Transmitters are hiding at places also Identified with a white and orange prism-shaped flag at each place.
  • Get a control card on which you must write your Name, Age, Address, and Phone number twice please.
  • Hand this card in to the Starterwho will give you the next available start time (in 5 minute intervals, but he will keep half of the card. Only after starting may you turn on your Direction Finding Radio, also called a “Sniffer”
  • Plug in the headphones. This turns the sniffer on. Tune and listen for the foxes’ call-signs (see below).
As you turn around, the signal peaks when the ferrite rod is broadside to the fox (front and back). To resolve the ambiguity about which way to go, press the red button to activate the telescopic antenna as well. This suppresses one of the signal reception lobes as seen by the signal strength graph shown here. The greatest accuracy is obtained when the signal fades out completely.

When you are very close to a fox, you will need to attenuate the signal (turn the volume down).
  • Each fox broadcasts its call-sign in slow Morse code on 3.51 MHz, 3.52 MHz, and 3.53 MHz respectively. They are:
       M   O   E  sounds like “dah dah   dah dah dah   dit “;
       M   O   I  sounds like “dah dah   dah dah dah   dit dit“;
       M   O  S  sounds like “dah dah   dah dah dah   dit dit dit“;
  • Time allowed is 1/2 hour. One point will be deducted for each minute late in returning. As you finish, we shall record your elapsed time, and compute your score. Control cards will be progressively displayed so that you may compare your score with others and discuss your strategies.;
  • As you find each fox, note its alphabetic identifying letter (ignore any numbers), thus scoring 20 points for each.
  • You must hand in your control card even if you abandon the course, otherwise we will think that you are lost and a search party may be sent out to find you.
  • TIP: Ask about “triangulation”. This means: from two or three different known places on your map, plot the bearings to all of the foxes that you can hear. (For this you may need a compass to orient your map.) Go that little bit further along the road to take more bearings, thus making a precise intersection of these bearings to show where all of the foxes are hiding. Then study your map to plan how to run around the park by the shortest route, scoring 20 points for each fox as you go. This is faster than bush-bashing towards each fox in turn. Remember to keep an eye on your time out on the course so as to avoid point deductions for being late back.
Webmaster Andrei ZL1TM   
Original Design Philip KG6CSM