Today's Message Index:
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1. 10:23 AM - Re: Transponder antenna (Kim Prout)
2. 11:27 AM - Re: Transponder antenna (Jos Okhuijsen)
Message 1
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| Subject: | Re: Transponder antenna |
Hello Fergus!
The typical transponder operating frequency is 1030Mhz (if I remember
correctly). This means a very large loss through the typical RG58 cable over
14 feet. (the higher the frequency, the higher the loss) Ideally the x-pndr
antenna should be mounted away from other reflective surfaces, that means
getting it above the engine or propeller face lines. (more distance/length
needed in the Europa installation) I used RG-233/U specified at 14.5 db loss
per 100 feet. Of course, make sure whatever you use it is 50 ohm impedance!
The antenna may be optimal but if there is a large loss of signal
strength/energy getting to it then that transponder system is compromised.
Hope this helps!
kp
Message 2
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| Subject: | Re: Transponder antenna |
Hi Kim,
The cable length used is probably less then 10 feet? The the loss will be
1.45 db.
That's neglectible. Even when 0.5 to 1 db per connector is taken in
account.
It's more important, as you said, to mimimize the blanking effect of
things like the engine.
While VHF frequency radio signals still bend around objects, Ghz signals
do not.
As somebody mentioned, far back in the tail, and as los as possible looks
like the best option.
But, if i have followed this thread correctly, most of the problems are
caused by having antennas in need of a ground plane without them, and
groundplanes added to non- groundplane dipoles.
--
Kind Regards,
Jos Okhuijsen
workshopcam http://www.okhuijsen.org/plane
http:www.europaowners.org/kit600
mono xs, top on, gear in, tail wheel in, wings set, flapdrive in, tail
closed, tailwheel in, tail top in, blue stuff filled, sanded and primed,
fuel system in, doors done, windows in, sanding and filling the fuse and
wings, engine installation, panel
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