A normal event has 5 check points plus the finish beacon. Which ones you hunt is up to you.

Five hidden transmitters working on the same frequency are timed to work in sequence.

No 1. transmits for 1 minute and then stops. As it stops, No. 2 starts, runs for 1 minute then stops etc. As No. 5 stops, No. 1 starts again and so it goes round. At anyone time, one and only one Transmitter can be heard but which one?

All Transmitters send out the letters M and O in very slow morse code, which sounds like
Dah dah,  dah dah dah followed by 1 2 3 4 or 5 dots which identify the Transmitter working at that time. So Transmitter No 3 would send dah dah,  dah dah dah,  dit dit dit. (3 dots).

Using the Receiver to find a Transmitter.

Each 80 metre receiver is fitted with a ferrite rod antenna. This is most sensitive when the Transmitter signal is 'broadside on' and least sensitive when the signal is 'end on'. Having heard a Transmitter, to locate it, first look for the minimum signal or null (this is accurate to 5 degrees). You then know that the Transmitter is in a certain direction but is it in front or behind you? By switching in a second antenna and a bit of electronic technology the main antenna pattern is altered to be more sensitive in one direction than the other to eliminate the 180 degree discrepancy.

Each 2 metre receiver is fitted with a Yagi beam antenna which is very directional. Just slowly move the antenna around until you hear the loudest tone and that is the direction of the hidden transmitter.

A plan of action: Standing at the start, you have one minute to find a bearing for a Transmitter. You can find them one at a time or spend 5 minutes getting a rough bearing for all 5. Then decide in what order to hunt them. But move, so as to be less visible to the next competitor who starts 5 mins after you.

 

Example

 

1st minute. Bearing of Transmitter No. 1.

 

Options: a). Move towards it taking repeated bearings until direction changes by 180 degs. or the minute runs out. Then find your location and take bearing on Transmitter 2 etc. By running to Transmitter No.1 you have committed yourself to find that one first. You may be moving away from the others.

b). Head off at 45 degrees to bearing to a known landmark and take 2nd bearing. To pinpoint Transmitter No.l, this must be done within the minute or wait 4 mins until it comes on the air again. Use the 4 mins to take bearings on the other 4 Transmitters.

c). From a known location sit tight for 5 mins and take a beainrg on all 5 Transmitters. Decide which looks the best one to do first, move to a new location and take 2nd bearings on some or all Transmitters. Now within 10 minutes, you have located not just the bearings but the approximate sites. Work out your best route. As you close in on a check point, take repeated bearings to improve your accuracy until you see the flag but also note that the volume of the signal increases as you near the Transmitter. Use the pin punch then quickly move away from the checkpoint so as not to give away its location. Visit them in any order and back to the finish in the shortest time.

 

The Finish Beacon continuously transmits the letters M O in Morse and on a different frequency to the other five.  If you get totally lost and are running out of time, tune to the finish beacon and head for it because your result, even if you have not found all of the Transmitters only counts if you report back to the finish within the time allowed. 2 found in 87 mins beats all 5 found in 91 mins!