Hangar Flying => Hangar Flying => Topic started by: GlennBob on May 07, 2007, 11:28:19 PM
Title: ELT antenna
Post by: GlennBob on May 07, 2007, 11:28:19 PM
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
Title: Re: ELT antenna
Post by: Joe Dubner on May 08, 2007, 08:25:32 AM
Quote from: GlennBob
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
Title: ELT antenna
Post by: Waiter on May 08, 2007, 11:39:53 AM
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
Title: ELT antenna
Post by: GlennBob on May 09, 2007, 12:40:03 AM
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.