[ PART 3 ] Extracted ( with permission ) from the RADCOM magazines issued by RSGB.
Near And Far Zones:
We now identify two zones around each hidden transmitter.
- The Near Zone is less than 200m from the transmitter and within this it is possible for the competitor to reach the Tx in 60 seconds that it is on the air in the five minute cycle.
- The Far Zone is defined as 400m to 1000m from the transmitter for even further out, although adjacent transmitters are very rarely more than 1km apart.
It is important to apply different tactics and techniques based on the zone in which you perceive yourself to be located.
In particular, a decision has to be made with regard to Overshoot vs Stop-short tactics.
Usually, top competitors will not stop-short and the reason is that once you have run the extra distance and ‘overshot’ the transmitter, the return is quicker than if you stop short and don’t know what is ahead.
- I agree that I had used the Overshoot mode more often than the Stop-short way, as it is easier to notice the signals dropping and the stronger signal is fromÂ the reversed direction.
Tactics For The Near Zone:
A short Stop-Before-Transmission tactic could be chosen, for which a good Attack Point is needed. This must be a place from which it is possible to move freely in as many directions as possible, and with visibility as good as any available in the competition terrain. A path crossing, a large clearing or bare hilltop are very good Attack Points.
Depending on the type of terrain and runnability the competitor should choose the appropriate techniques for finding the hidden transmitter. The choice is to Run-directly, Aiming-off or lastly Spiral techniques.
While the Run-directly technique is self-explanatory and the most popular, the Aiming-off technique is also useful. With this, the competitor runs at a slight angle (5-10 degrees) to the perceived direction of the transmitter. As a result, the competitor only has to look to the one side for a glimpse of the control flag at the transmitter or, for that matter, other competitors already in the vicinity of the transmitter. If there is a path leading in a slightly different direction to the direction of the transmitter, a good technique is to run fast down the path, constantly taking bearings and when the bearing is 90 degrees away from the path, to then move in that direction towards the transmitter.
This technique could help if the area is bushy with extensive undergrowth or low visibility.
However, if the area is open or easily runnable probably the Run-directly technique will work better.
- The first time I had no choice but to use the Run-directly technique, was in IARU R3 ARDF event in Australia because this idiot lost his map after leaving the end of the start corridor. So happily burning energy going up and down the dunes, just following the loudest signal strength. Next time everything needs to be tiedÂ to my body.
The Spiral technique is similar to the Aiming-off technique, however the competitor will intentionally over-run the transmitter and then, by constantly changing their direction to the left or right as indicated by the bearing to the transmitter, will move along a spiral path. This tends to happen anyway when attempting to run directly by virtue of the time delay between sensing that the bearing is swinging to one side or the other, and reacting by changing the direction of run.
Once a closing spiral circle is established, the competitor will have confidence that the transmitter is within the spiral/circle area. This is very useful in bushy areas and in high undergrowth with low visibility.
- Spiral method was effective when I hunting my final fox in Ubon, Thailand. There was a small bush with a tree in the middle of a recently tilled field. I overshot it initially but went back to that up-crop and moved around it to find the fox beacon.
More to be published in Part 4 ….