Hi Kenny:

I am a pilot, and member of local Search and Rescue, and a ham and regularly
practice hunting down ELT transmitters.

The first thing I found was that a number of the sources of ELT
transmissions come from aircraft at airports.

One of the first things I learned was that normal ELT equipment does not
work well when you are looking at number of close aircraft. The normal
equipment is overloaded, and hangars cause reflections.

Since signal strength decreases with the square of the distance, the easiest
starting point is go to the local airports and see if the signal is strong
or weak. Listening on a handheld radio, the signal gets weak in a few miles
or less. Another trick with the handheld is to hold your radio at your
stomach and turn 360 degrees. Your body will shield the signal, so your
back will point to the source.

For greater distances, build a simple 3 element yagi (dimensions on the web
under "ELT yagi dimensions" or something like that. Build one so the
elements easily remove from the boom and it can be stored until needed. The
yagi simply points to the source for maximum signal strength.

One simple method of finding the ELT units in a hangar full of aircraft is
to remove your antenna and walk around from airplane to airplane until the
signal is the strongest. Even then, it may overload. We have built crystal
sets and use radios tuned to harmonics for close work, but that is beyond
simple.

The last time we found an ELT inside a hangar, the local manager was sure
that the airplane I determined was the offender could not possibly be the
one because it had just been annualed that afternoon (duh). It was - lousy
solder work in replacing ELT battery.

Often the local ham group or CAP group will have a hidden transmitter hunt
to practice. It is fun and educational.

If you want something dedicated, you can obtain an old comm unit that tunes
to 121.5 and use the receiver only in your car, with a 3 element yagi or 2
element quad and find stuff in a hurry., with practice.

The designated practice frequency is 121.775 MHz. Do not practice on 121.5.
Unfortunately, the older comm units do not cover the practice frequency.

Colin N12HS, K7FM, Yamhill County Sheriff's Search and Rescue.