BASIC TECHNIQUES
If you don't have some sort of attenuator between your antenna and the receiver, as you approach the hidden transmitter the signal will soon be so strong that it won't seem to diminish no matter which way you turn. Remove the entire antenna and try again. You may even have to tune your receiver 5 or 10 Khz away from the hidden transmitter's frequency. You'll probably still be able to hear it, but it should now be weak enough to allow "body fade" to again work. Some novice RDF'ers in our group's on-foot hunts have been quite successful with just this simple method.
If you're using a simple VHF beam the technique is pretty straightforward. Simply rotate the antenna until the signal seems the strongest, as indicated by your signal strength meter, and then the antenna should be pointing in the direction of the hidden transmitter. As you get close, you'll have to use attenuation of some sort to reduce the strength of the signal going in to your receiver, to keep the signal within range of your S-meter. And again, you may find that tuning 5 or 10 Khz off frequency helps reduce the received signal strength to a usable range, as we've described earlier.
Small beams designed for the third
harmonic of the hidden transmitter's frequency work the same
way, but since these beams are physically smaller some hunters like them
because they're easier to tote around. You will still need to use an attenuator
or use the "tune off frequency" method when you get very close. As we mentioned
before, if you want to try this route you should know that the third harmonic
signal is normally MUCH weaker than the "fundamental" frequency
of the transmitter you're hunting, so you will likely not be able to hear
it from very far away. You'll usually have to be quite close to the hidden
transmitter before you get any usable signal. But since beams for the 70
cm. band are quite a bit smaller than those for 2 meters, you can carry
around an antenna with many more elements, and therefore better gain and
directionality.
Hudson Valley Direction Finding Association
Copyright 1998, 1999,
2003, 2014 John Hirth W2KI
All Rights Reserved