---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Sat 06/23/18: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 08:34 PM - Transponder and ADSB antennae question. (Robert Reed) 2. 09:48 PM - Re: Transponder and ADSB antennae question. (The Kuffels) ________________________________ Message 1 _____________________________________ Time: 08:34:09 PM PST US From: Robert Reed Subject: AeroElectric-List: Transponder and ADSB antennae question. I am in the process of locating best place to install the transponder and ADSB antennae. I have been building for way too long and as a result some things planned years ago are no longer viable. I initially installed two Archer NAV antennae, one in each wing. Now I see little or no need for either antennae and have no plans to install other than GPS. My question is rather I could disconnect the coax to those antennae, install the transponder and ADSB in the wing bottom and use the existing coax? I cant remove the NAV antennae since I bonded them to the underside of the wing top. Will the old antennae interfere with the transponder or ADSB? Any other issues to consider? If I later decide to install a NAV system will it interfere with either unit? Bob Reed ________________________________ Message 2 _____________________________________ Time: 09:48:09 PM PST US From: "The Kuffels" Subject: Re: AeroElectric-List: Transponder and ADSB antennae question. Robert, << disconnect the coax to those antennae, install the transponder and ADSB in the wing bottom and use the existing coax? I cant remove the NAV antennae since I bonded them to the underside of the wing top. Will the old antennae interfere with the transponder or ADSB? Any other issues to consider >> First a confusion. Vanilla ADSB units have only one combined ADSB/transponder antenna. Why do you need two? Second confusion. Archer antennas need a metal wing to act as a counterpoise. How are the Archer antennas bonded inboard of the wing tip. Either you have a non-metal wing with no counterpoise or you have a shielded antenna. Obviously there is something here I don't understand. Potential problems: By the wing bottom I assume you mean the bottom at the center of the wingspan. Besides the extra complexity of a remote ADSB unit vs. a panel mount you are faced with the manufacturers limit on cable length, usually about 10 feet, because of cable signal attenuation. Most of ADSB is still ground based. Thus the ADSB antenna needs a 360 degree view of the ground to function fully. At the wing tip much of the ground (even half) is blocked. This will result in spotty performance and whines from ATC each time your transponder signal drops out. ADSB/transponder antennas are ground plane type. A short spike is mounted on an 8 inch or so circle/octagon/etc. Mounting this antenna with the spike horizontal and facing outward would shield the antenna from any conducting metal inboard. But this also guarantees maximum signal blockage. Mounting the ground plane on the bottom of the wingtip with the spike protruding downward would work better. If it were me, I'd mount the antenna on the bottom of the fuselage. On my Sportsman, it is mounted to the underside of the fuselage cage with the spike protruding through the fiberglass fuselage shell about 1 inch. Tom Kuffel --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-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/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-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.