NTSB F-16 & Cessna 150 midair preliminary report

Ramy wrote:
A note about transponder altitude inaccuracy. I also noticed significant
inaccuracy when I used the Zaon MRX but once I switched to PowerFlarm I
found mode C reported altitudes much more accurate, so I suspect the
significant inaccuracy that Dan noted is due to MRX error, not
necessarily transponder error.

Ramy

You may get larger MRX errors if the glider does not have a local
transponder (that is being interrogated and seen by the MRX)...if it does
the MRX will use the transponder's transmitted altitude instead of it's
internal pressure sensor--which can be affected by cockpit ventilation.
With the number of issues that I believe Ramy had with his MRX maybe it was
not properly identifying the local transponder.