Transponder antenna ground plane

[C5Engineer 1170]

How did you guys running transponders mount your antenna? I am running a microair transponder with the AK-350 encoder and Rami AV-22 knock off Ted antenna. Working on the plane tomorrow and would like to get this part done but I want it to work. I read about 20 articles till my head hurt and never got a good answer for this type of set up. 

[chopndrag 226]

Did mine on the belly on every aircraft I've owned . 

[EDMO 1078]

Joey,  I've been away from electronics too long, but if you mount your antennae on the belly and either mount it on or back it up with a piece of metal or even aluminum foil with a minimum surface or diameter of 2x the height of your antennae you should be fine.  Larger would be OK too.   Make sure it is grounded good.   EDMO

Edited 4 Feb 2017 by EDMO

[Av8r3400 1179]

The Kitfox mount is about 3 x 4" plate welded to the airframe on the belly, just behind the cabin on the pilots side.  That's where both of mine were/are and there is no issue with transmission.  

[Geoffrey Thorpe 31]

FWIW I attached a chunk of aluminum sheet to some of the tubes on the bottom with Adel clamps and mounted the antenna to the middle and poked it through a hole in the fabric. I bent the edges of the sheet up a bit to reduce the chance of a chafing problem. Also grounded the plate to the airframe.

Edited 6 Feb 2017 by Geoffrey Thorpe

[nlappos 413]

I mounted the small post antenna on my belly, almost between the pedals, so it is on that thin aluminum floor. I just drilled a 1/2" hole and mounted it with a lock washer. This is an excellent ground plane, and also convenient since the short BNC cable just drops down from the panel. The Xponder checks out fine with ATC.

[C5Engineer 1170]

Ended up with this set up. Attached it with a couple of hose clamps.