MRX PCAS displays wrong code and altitude for my transponder

On Apr 5, 6:21*am, Andy wrote:
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?

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?

-Tom

First check that the internal baro sensor is set correctly.
Calibration instruction are in the manual. *Then you can try adjusting
the suppression level. * It's on page 2 on the calibration menus.
Call ZAON product support for help with that.

A local ASW-27 pilot has a TT21 with antenna mounted near the rudder
pedals and I have not heard him complain of problems with his MRX.

If in doubt send it back for calibration *Mine had degraded to the
point it was useless and ZAON fixed it for me at no charge.

Andy

Its not clear from this if the '27 has a dipole or stub/ground plane
antenna mounted here. One problem with an L2 style dipole antenna near
things like rudder pedals is they are more susceptible to conductive
objects. Moving the rudder pedals neat the antenna may even cause
problems (even maybe a Becker E10 error that I understand Tom has seen
at times in his install).

Its also just a bad idea to bathe all the other electronics in the
cockpit with strong RF signals from the transponder. You may get away
with it but its just not a good idea, and may cause problems that are
hard to track down.

Many manufacturers, including Schleicher, publish tech notes with
approved/recommended transponder installation procedures for a reason.
The Schleicher notes are well written and worth following, including
where to properly mount a transponder antenna, how to properly install
a ground plane etc.

Darryl