ELT locator

I am looking to build a ELT locator that works. We had a feasco last
week when a elt went off. It took 2 1/2 hrs for the faa, sheriff, fbo,
civil air patrol. to find it and it was in a hanger at the second
airport they looked at. Thanks for your help. Kenny

Kenny wrote:
I am looking to build a ELT locator that works. We had a feasco last
week when a elt went off. It took 2 1/2 hrs for the faa, sheriff, fbo,
civil air patrol. to find it and it was in a hanger at the second
airport they looked at. Thanks for your help. Kenny


If you have a handheld aviation comm, you already have all you need to
locate an ELT.
Any CAP cadet can show you how to adjust the squelch and move around to
locate the signal.

Kenny wrote:
I am looking to build a ELT locator that works.

--------------------------------------------------------

Dear Kenny,

Try making contact with you local amateur radio club. (Go to a
meeting. Stand up, introduce yourself, explain the problem and ask for
their help.)

Tracking down transmitters, hidden and otherwise, is both a chore and
and obligation. To keep their skills sharp hams hold practice 'fox
hunts' in which the fox is the transmitter. The equipment is
inexpensive and fairly primitive but works well enough once you've
learned how to use it. The basic principle is to put an electrical
switch between a pair of antennas. The circuit switches from one
antenna to another at a rapid rate. When the antennas are broad-side
to the transmitter the signal is equal and you may scribe a line of
position. (Sexier models use multiple pairs of fixed antennas and an
array of LEDs to indicate the line-of-position.)

Once you have a line of position you move the receiver some distance
away, perpendicular to the line of position, and take another reading.
The apex of the resulting triangle will indicate the approximate
location of the transmitter's antenna. (A club or group will have
fixed locater systems at their home stations and will simply call-in
their observed line-of-position to a central controller.)

Low-end systems cost as little as $20 and connect to a hand-held
receiver.

-R.S.Hoover
-(KA6HZF)

On 2 Apr 2005 19:21:10 -0800, wrote:


Kenny wrote:
I am looking to build a ELT locator that works.

Last week I checked E-Bay for RDFs and found over half a dozen. Don't
think any of them hit $100. 2 of them will locate any transmitter to
within a couple hundred yards from a distance of several miles. 3 or
more makes the fix easier.

--------------------------------------------------------

Dear Kenny,

Try making contact with you local amateur radio club. (Go to a
meeting. Stand up, introduce yourself, explain the problem and ask for
their help.)

Tracking down transmitters, hidden and otherwise, is both a chore and
and obligation. To keep their skills sharp hams hold practice 'fox
hunts' in which the fox is the transmitter. The equipment is
inexpensive and fairly primitive but works well enough once you've
learned how to use it. The basic principle is to put an electrical
switch between a pair of antennas. The circuit switches from one
antenna to another at a rapid rate. When the antennas are broad-side
to the transmitter the signal is equal and you may scribe a line of
position. (Sexier models use multiple pairs of fixed antennas and an
array of LEDs to indicate the line-of-position.)

Once you have a line of position you move the receiver some distance
away, perpendicular to the line of position, and take another reading.
The apex of the resulting triangle will indicate the approximate
location of the transmitter's antenna. (A club or group will have
fixed locater systems at their home stations and will simply call-in
their observed line-of-position to a central controller.)

Low-end systems cost as little as $20 and connect to a hand-held
receiver.

-R.S.Hoover
-(KA6HZF)

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.

Kenny wrote:
I am looking to build a ELT locator that works. We had a feasco last
week when a elt went off. It took 2 1/2 hrs for the faa, sheriff, fbo,
civil air patrol. to find it and it was in a hanger at the second
airport they looked at. Thanks for your help. Kenny

You should be breaking out the champaign to celebrate them finding it in
only 2 1/2 hrs.

I know of a case where it took 3 days to find one on a ramp. The
satellite told them to look 40 miles NE of where the plane was sitting.

Kenny wrote:
I am looking to build a ELT locator that works. We had a feasco last
week when a elt went off. It took 2 1/2 hrs for the faa, sheriff, fbo,
civil air patrol. to find it and it was in a hanger at the second
airport they looked at. Thanks for your help. Kenny

Dig around in the Ham Radio Direction Finding stuff. We dabbled a little
in the past. My wife built one of these doppler finder kits which worked
OK...up close (like on an airport ramp) all you need is a handheld, a step
attenuator between the antenna and the receiver makes it easier but pulling
off the antenna and other games can work as well.