ELT antenna

[GlennBob]

How tough is it to make an  ELT  antenna ?

My  AMK - 450 unit  ( that's the one that has the replaceable duracel batteries ) still has the BNC connector on it but there's no wire antenna coming from it.  

I checked on ordering a new one.  It can be had . . .but for $ 51.00.  Seems a little steep for what I think is just a wire.  12 "  or  24 " long.

Glennbob

[Joe Dubner]

How tough is it to make an  ELT  antenna ?

Easy, but not a survivable or particularly effective one in a composite aircraft.

A quarter-wave dipole is about 23 inches at 121.5 MHz.  If I were to do this (and ignoring the requirements of the TSO) I would weld or braze a small diameter stainless steel rod to the center pin of a female BNC connector and pot it with epoxy inside the connector to provide mechanical strength.  Copper wire or even a copper tape whip would be electrically effective too but not as rugged.   Similarly, running coax to an external antenna would be electrically effective.

[opinion]
Or you could just fly around with the broken-off antenna :-)  That's about as effective as the typical 121.5 MHz ELT IMO (based on my experience with ELT searches in the Civil Air Patrol where all we ever found were false alarms -- the actual ELT events were almost impossible to pick up unless very close).  YMMV of course.  And the newer 406 MHz ELTs are a whole different story.
[/opinion]

--
Joe

[Waiter]

I purchased a "rubber ducky" antenna, its about 8 inches long. It connects directly to the ELT using a 90 deg BNC connector/adapter.

Although not as efficient (RF wise) as other antennas, ods are real good, this antenna will not get ripped out of the ELT during a crash.

Google "Ham Radio VHF rubber ducky"

Waiter

[GlennBob]

Thanks guys,

Yeah . .  Joe, . .

That's about what I'd heard about the  ELT's .    About as effective as a visual search.   You gotta comb  an area of about a square mile or more back and forth until you find your target.

Thanks for the suggestions.   I'll figure somethin' out.

Glennbob