MRX PCAS displays wrong code and altitude for my transponder

On Apr 4, 10:19*pm, 5Z wrote:
The MRX is mounted on top of the glare shield and the Becker is driving a L2 antenna mounted in the nose of my ASH-26E, just forward of the rudder pedals.

When I squawk 1201, the MRX shows 1236 (or other 12xx code) and the altitude is about 500' lower than what's on the Becker.

Are the antennas too close to each other?

Yes. Even if this is not actually causing your problem (and I suspect
it is) this is a bad configuration.

An antenna around the rudder pedal area like this is not ideal, there
are too many conductive objects in the near field region of the
antenna and too many with dimensions likely to cause problems. The
best position is where the factory recommends and its not too hard to
do, but does require pulling the engine to access the engine bulkhead
interior to do the install. Well documented in a technical note by the
factory.

I'm thinking of putting a sheet of foil just under the MRX and forward to provide some shielding from the xponder antenna. *Since the MRX is attached to the glare shield, which in turn is attached to the canopy, I could also install a length of coax and place the MRX antenna by my shoulder on the canopy rail.

Thoughts?

Yes. Install the transponder antenna properly. :-O

You are bathing everything behind your panel in fairly powerful RF
pulses. If you want to install a PowerFLARM or other things later you
may find additional problem with that, besides its PCAS stuff not
working either. So instead of trying tinfoil bandaids I would start
again and do it properly.


-Tom


Darryl