Running a Radio-Orienteering Course

Filed under: Radio Orienteering by Joseph on November 4th, 2018

Here is your train of thought while running a course…

You are called up to start and given your map. Only the start and finish are shown and you need to find the 5 foxes (radio transmitters) that are out there. You study the trail system and try to guess where the foxes could be. They must be spaced at least 400m from the finish and each other as well as 750m from the start. You make a tentative plan. Then your time starts, you plug in your headphones and you can hear fox-1 broadcasting it’s Morse code signal. You run along the marked corridor listening to fox-1while rotating your radio receiver because you can tell the direction to the fox by the volume of the signal when your receiver is pointing to the fox.

Now that you are out of the corridor you stop to get an accurate bearing to the fox and draw a line on your map from where you are along the direction to the fox. The signal appears to be coming from an area closer to the finish, so you don’t head toward it, you continue running along the trail as you planned.

At the end of the first minute fox-2 comes on. Again you stop to take a bearing and draw the line on your map. By the time you have run out of the 750m exclusion zone from the start you have had a chance to listen to all 5 foxes.

Fox-4 sounds closer than the others, but it is off to the the west, in the direction of the finish while fox-3 is more to the east. You need to decide if it makes better sense to get the close one first or save it for the way back to the finish. It is a tough decision because the distance estimation isn’t very good. You decide to head away from the finish to get fox-4, and you’ll pick fox-3 up on the way back to the finish.

There is an intersection coming up where you can take a trail that is going somewhat toward fox-3. As you close in on fox-3 the signal gets louder, and the closer you are the faster the volume increases. You know you are close, but then the fox stops transmitting. It will be 4 minutes before it starts up again. You’re guessing that it is probably within 200m, so you continue on the bearing you took before it went off. There it is. You punch the control and start heading back to fox-4.

While you were running to fox-3 and then fox-4 you took several bearings to the other foxes, so now the intersections of those lines give you a rough idea of their locations. It looks like you made the right choice to save fox-4 for for later, but now you decide to get fox-1 next and then fox-4.

You are not taking many bearings now. Mostly just quick checks to confirm that your calculated locations are still making sense. Route choice decisions are now paramount. You need to get close enough when the fox is on so you can follow the heading even if it goes off.

Fox-1 comes on and you realize you’ve already passed it while running on the trail. As you run back you try to keep track of its direction and then it goes off. You use the bearing until it seems like you have gone too far and then start a searching in different directions. No luck. Finally it comes on again . Wow it is loud – you’re close. Someone else is running toward it from another direction. You see it and punch in.

You check your watch. 50 minutes. You have plenty of time. The limit is 150, but if you are late you are disqualified.

The next foxes go pretty well. You got fox-2 off cycle and lucked out because fox-5 came on just as you got close. All that is left is to get to the finish. You adjust your frequency to the finish beacon which thankfully stays on all the time. You decide on a route and run toward the finish. You see the control at the beacon, punch it, and run in to the finish.

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