---------------------------------------------------------- Europa-List Digest Archive --- Total Messages Posted Wed 12/20/06: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 10:23 AM - Re: Transponder antenna (Kim Prout) 2. 11:27 AM - Re: Transponder antenna (Jos Okhuijsen) ________________________________ Message 1 _____________________________________ Time: 10:23:02 AM PST US From: Kim Prout Subject: Re: Europa-List: 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 _____________________________________ Time: 11:27:23 AM PST US Subject: Re: Europa-List: Transponder antenna From: "Jos Okhuijsen" 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 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message europa-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Europa-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/europa-list Browse Digests http://www.matronics.com/digest/europa-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.