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Old 06-12-2018, 03:57 PM
MConner MConner is offline
Join Date: Mar 2018
Location: Snead Island, Florida
Posts: 205
Default ELT antenna for com 2

My ELT antenna is mounted in the baggage compartment with the base at the top longeron and extending upwards in the fiberglass top. For length, it bends toward the center of the roof with about 1/2 of it mostly vertical.

I am adding a #2 comm radio and am thinking this type of antenna install might work since most of what I use it for is receive.

Anyone tried an ELT antenna for comm? Should be close as 121.5 is in the comm band.

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Old 06-12-2018, 04:17 PM
BobTurner BobTurner is online now
Join Date: Dec 2011
Location: Livermore, CA
Posts: 5,660

Just a comment. Your mounting location provides a very much less than ideal ground plane, with virtually no ground plane extending to the outboard side. For 1/4 wavelength antennas like this the ground plane is part of the system.
Having the top half of the antenna horizontal is not a huge deal (might cost you 10%?).
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Old 06-12-2018, 04:27 PM
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Mel Mel is online now
Join Date: Mar 2005
Location: Dallas area
Posts: 10,276

Another small point; the diameter of the antenna affects bandwidth. The ELT antenna is small in diameter and therefore has very little bandwidth.
i.e. The further you get away from 121.5 Mhz., the less the gain of the antenna.

Bottom line; Not a very good idea.
Mel Asberry..DAR since last century
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Old 06-13-2018, 10:53 PM
MConner MConner is offline
Join Date: Mar 2018
Location: Snead Island, Florida
Posts: 205
Default Ok tried it

tried the ELT antenna in the baggage area for com 2. Receive Works at about 85% as well as com 1 to the front, seems a little weak to stations behind me. Transmitter was reported 5 x 5 by ATC 40 miles in front. Have not tried behind. Think it is due to ground plane efficiency.

Have not tried all frequencies yet.

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Old 06-14-2018, 03:30 PM
Canadian_JOY Canadian_JOY is offline
Join Date: Aug 2007
Location: Ontario, Canada
Posts: 1,960

If your ELT antenna is one that has a "lump" in it, this is often a tuning device which helps the antenna radiate not only on 121.5 but also on 243.0 MHz. With this being the case, use of these antennas for COMM operations is not a good idea. If you really want a 2nd COMM, install a 2nd COMM antenna.
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Old 06-17-2018, 09:35 AM
MConner MConner is offline
Join Date: Mar 2018
Location: Snead Island, Florida
Posts: 205

Com 2 is there for a back up similar to carrying a hand held. It is nice to be able to listen to an ATIS or monitor a CTAF while still talking to ATC on com 1. The transmitter works better than a hand held in case com 1 fails. No holes in the plane and no drag from the antenna. The ELT antenna was surplus so saved a few dollars. I am happy.

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