Using Hand Held VHF for ELT Location

[kontiki]

Anybody have any experience in using a handheld VHF for 121.5 ELT location?

Ran into this last week, finally got it buy process of elimination, but it took time and some work.

It occurred to me that if there was some kind of coffee can shield (or something) that could be placed over the 1/4 wave whip of a hand held it might be useful as a direction finder.

Anybody ever try this or know something about it?

 

[murphey]

What you are looking for is the detector attached to a big-gish antenna that you can carry around. We use one with CAP cadets to find ELTs that have gone off on the ground.

 

[Hiperbiper]

No coffee can needed, tune handheld off freq around 122.5 to 123.5...drive around the airport. When you pick up the elt on 123.5 you're around close...
We had an elt sounding at dtn a few weeks ago, CAP guy pinpointed it to two different hangars on the east side of 14. I found it with my handheld on the far west side of the airport...

Chris

 

[GaryV]

I use my handheld to find ELT's in the hangers at my airport several times a year. When it peaks high enough that I can't tell when I'm getting closer I tune off frequency a little. That will usually get me within 1 or 2 hangers. At that point I remove the antenna.

With the antenna off the handheld and detuning I can get it to the point that I have to put the connector in the gap in the hanger door of the hanger the plane is in to here the signal. So far I've found 7 or 8 planes with the ELT on and have never picked the wrong hanger

Gary

 

[G-force]

In ham radio, we have contests called T hunts (transmitter hunts.) A battery powered transmitter is hidden some where in a city and we have to find it. Its common to use a hand held, directional antenna, usually home made. This is one example: http://theleggios.net/wb2hol/projects/rdf/tape_bm.htm Granted these are tuned to the 2 meter ham freqs, in the 140mhz range but should work fine for 121.5 When we get within a few hundred yards, we use whats called body shielding technique. Remove the antenna and hold the radio close to your chest. Turn around in a circle slowly, when you loose the signal, or find its weakest signal, the source is behind you.

 

[denverpilot]

Body shielding, de-tuning or attenuation pads, and eventually removal of the antenna for serious attenuation... yup. Finding a transmitter with a handheld receiver is not as easy as some methods but works fine.

Wing-null method when the receive antennas are mounted on top of a Cessna wing, by banking the aircraft and blocking the signal source, also works.

RF physics is RF physics. It doesn't change, even if the fancy direction finding gear fails.

Been on many a "t-hunt". Beating the guys and gals who spend big money on Doppler DF gear to a "fox" transmitter, using only simple gear and homemade antennas -- is a ton of fun. The longer you're sitting there at the "fox" waiting on them, drinking a soda and enjoying the wait -- the better.