Transponder & ADSB antenna location?

[Steve SR]

Building a Progressive Aerodyne SeaRey, just wanted to challenge the "We always do it this way" thinking and am looking for alternative locations for the Transponder/ADSB antennas. Instead of running the wires all the way out to separate wings, I was thinking about putting them inside the fuselage (aluminum frame, fiberglass body/hull). GPS antenna goes on the glaseshield, so the other antennas will have to go in the aft part of the hull/fuselage.


Thoughts? Already saw this thread https://forum.flydynon.com/threads/transponder-antenna-location-safety.13677/



Thanks

 

[GKC Aviation]

Should be fine under the fibreglass body in the aft fuselage, Glassairs do a similar thing..
You will need a ground plane of about 100mm x 100mm, make it from a sheet of thin aluminium.
Transponder and ADSB antennas need to be at least 2 ft apart, further if you can.
Antennas obviously need to be pointing down (or up, but preferably down).

 

[Steve SR]

Thanks.

I know there must be a reason why not, but I wonder if I could just mount one of them to the underside of the avionics tray, but at least 3' away from the GPS antenna? Probably too much interference from the power buss and other avionics.

 

[Rhino]

You might get away with no interference with the GPS, but there are tons of stories out there about transponder antennas interfering with intercoms when too close to the cockpit. The only way you'll know for sure is to try it. Make sure you you use very good shielded cable for the antennas. Most use RG-400.

 

[Steve SR]

Thanks. In the long run, RG cable is cheap compared to living with interference. Shoutout to Steinair for patiently taking and answering my calls. Buying as much from there as I can instead of ACS, gotta support small businesses.