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ELT Antenna Length

 
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tinnemaha(at)hotmail.com
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PostPosted: Mon Jan 09, 2006 10:15 am    Post subject: ELT Antenna Length Reply with quote


I know this is a dumb question, but I think it would be dummer for me not to
ask: In order for it to fit in what I believe to be the best location, I
need to shorten my ELT antenna from 21 inches to 19-3/8 inches. Will that
adversely affect performance? Another location will be very difficult. Can
anyone suggest another solution?
Thanks,
Grant


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skywagon(at)charter.net
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PostPosted: Mon Jan 09, 2006 12:02 pm    Post subject: ELT Antenna Length Reply with quote


Grant,
If you were able to add a "loading" coil to the antenna correctly, this
would allow you to shorten the current antenna. You would need a guru type
friend that knew antennas to accomplish this for you. However, I would bet
that a search of the web via Google would find a manufacturer that makes the
"loaded" antennas for the frequency that you need.
David


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nuckollsr(at)cox.net
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PostPosted: Mon Jan 09, 2006 5:44 pm    Post subject: ELT Antenna Length Reply with quote


At 10:15 AM 1/9/2006 -0800, you wrote:
I know this is a dumb question, but I think it would be dummer for me not to
ask: In order for it to fit in what I believe to be the best location, I
need to shorten my ELT antenna from 21 inches to 19-3/8 inches. Will that
adversely affect performance? Another location will be very difficult. Can
anyone suggest another solution?

I did some tests on a bizjet installation where we substituted
a "rubber-duck" of a VHF-Comm hand-held for a full sized 21 inch
antenna. Differences in gain and pattern were barely discernable.
Bob . . .

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BigD(at)DaveMorris.com
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PostPosted: Mon Jan 09, 2006 6:35 pm    Post subject: ELT Antenna Length Reply with quote


An ELT is an insurance policy you hope to not have to use. Changing the
length by 8% will cause the transmitter to no longer reach its maximum
distance. Maybe instead of 40 mile range you only get 35. If by
shortening it, the SWR goes up to the point that the automatic overload
circuitry trips in the ELT and shuts off the transmitter, that wouldn't be
good either. Ask the ELT manufacturer about that. If you're going to be
doing a lot of flying over the Amazon, you might reconsider.
A better question might be what is limiting the length to 19 3/8? Is it a
metal panel? Proximity to metal would be an even more serious problem than
an 8% shorter antenna. Can you bend the antenna and keep its length?
Dave Morris
At 12:15 PM 1/9/2006, you wrote:
I know this is a dumb question, but I think it would be dummer for me not to
ask: In order for it to fit in what I believe to be the best location, I
need to shorten my ELT antenna from 21 inches to 19-3/8 inches. Will that
adversely affect performance? Another location will be very difficult. Can
anyone suggest another solution?
Thanks,
Grant


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nuckollsr(at)cox.net
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PostPosted: Mon Jan 09, 2006 7:21 pm    Post subject: ELT Antenna Length Reply with quote


Grant,
Is this antenna "inside" or does it mount out in the breeze?
Bob . . .
At 12:01 PM 1/9/2006 -0800, you wrote:
Grant,
If you were able to add a "loading" coil to the antenna correctly, this
would allow you to shorten the current antenna. You would need a guru type
friend that knew antennas to accomplish this for you. However, I would bet
that a search of the web via Google would find a manufacturer that makes the
"loaded" antennas for the frequency that you need.
David


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wschertz(at)ispwest.com
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PostPosted: Tue Jan 10, 2006 8:15 pm    Post subject: ELT Antenna Length Reply with quote


Go to a wood working store/catalog and by a drill bit for boring through
lamp bases ~18" long, then you could go up through all three ribs if I
understand your statement below correctly.
Bill Schertz
KIS Cruiser # 4045
I want to
Quote:
mount the base of the antenna in the fuselage & extend the antenna up into
the already covered portion of the vert stab.
The antenna that came with my ELT has a ~3" high rubber cone at the base
out
of which extends about 18 more inches of small diameter metal rod. I
drilled small holes in the bottom two ribs of the stabilizer, but the
third
one I can't reach with a drill bit.


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