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juliant
Joined: 22 May 2008
Posts: 30
Location: Koromatua, New Zealand
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| Posted: Sun Sep 28, 2008 2:46 pm Post subject: Transponder aerial |
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Hi
What is the best place to mount the transponder aerial? and what sort of ground plane is required . Anyone got any pics?
thanks
Julian
NZ |
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gme9261236
Joined: 27 Jan 2007
Posts: 109
Location: Hampton, NH 7B3
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| Posted: Sun Sep 28, 2008 3:06 pm Post subject: |
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| I do not have a pic but mine is mounted just under and slightly behind the pax seat (but still forward of the rear cargo). It has a 10" piece of stainless steel for a base and is mounted facing down with the stainless on the inside of the plane. Works great with no problems. |
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b1x4nqb
Joined: 14 Aug 2006
Posts: 232
Location: Orwigsburg, PA
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| Posted: Sun Sep 28, 2008 5:54 pm Post subject: Antenna's |
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Do a search on "antenna mounting" and you will find some good info from Wes. Here is the link, if it works.
Paul, PA
http://www.wingsforum.com/viewtopic.php?t=12548&highlight=antenna |
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gme9261236
Joined: 27 Jan 2007
Posts: 109
Location: Hampton, NH 7B3
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| Posted: Sun Sep 28, 2008 9:56 pm Post subject: |
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| I forgot to mention WES. He is absolutely the go to avionics guy on this site. |
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juliant
Joined: 22 May 2008
Posts: 30
Location: Koromatua, New Zealand
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| Posted: Mon Sep 29, 2008 2:33 pm Post subject: |
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Thanks link works fine.
Useful stuff.
Julian
NZ |
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jak
Joined: 17 Mar 2008
Posts: 15
Location: toccoa Ga
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| Posted: Sat Oct 04, 2008 12:18 pm Post subject: |
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| Julian I've been trying to post a reply to you for threee days and my piece of crap computer hasn't let me. Anyway here at the factory we put the transponder ant. on the plate that covers the opening at the rear on the bottom of the fuse. That way no additional metal has to be put into the bottom of the plane. Jak |
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b1x4nqb
Joined: 14 Aug 2006
Posts: 232
Location: Orwigsburg, PA
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| Posted: Sat Oct 04, 2008 12:29 pm Post subject: |
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I know little about this stuff but I thought you wanted the antenna and actual transponder as close to each other as possible. Does that have any effect on the signal strength with a loss due to the longer length?
Paul, PA |
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jak
Joined: 17 Mar 2008
Posts: 15
Location: toccoa Ga
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| Posted: Sun Oct 05, 2008 7:22 pm Post subject: |
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| There has to be at least 9 ft of cable for the numbers to work when we hook it up to do the certification. It dosn't hurt for it to be longer. Jak |
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Wes
Joined: 23 Jan 2006
Posts: 111
Location: Satellite Bch, Florida
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| Posted: Sun Oct 05, 2008 9:38 pm Post subject: Transponder Antenna Mount |
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Wooohhh, wait a minute guys, are we talking about transponder antennas?
Transponders operate around 1 GHZ and the signal attenuation in coax at this freq is terrible. Some coaxes are better than others, but readily available coax types that are over 6 ft in length will attenuate the TX and Rcv signals well in excess of manufacturer reccomended specs. (1.5 db max. for the Garmin 327).
So again, in my opinion you are severely compromising your ATC transponder system if you run long, lossy coax to the tail mounted antenna. Will it 'work' ?, well maybe, - will it work on the edge of the radar coverage area, where you really might like to have it ? - probably not!
In this case, longer is definitely not better!
'Just' my opinion.
Wes |
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