"Chip Jones" wrote in message
...
A couple of years ago we had a guy flying through GRB approach airspace
always had bad Mode C. But it was only bad with GRB approach, no other
facility had a problem with it. He had it checked at an avionics shop
and
they found nothing wrong.

Yep, this kind of Mode C anomoly happens in ZTL airspace too. That's one
reason we always go with pilot reported altitude over Mode C readout.

First time I was called on an inaccurate Mode C by ATL, I took it to the
shop. They said it was OK and serviced it anyway. ATL called me on it
again but it's fine everywhere else, almost....

Anytime I fly from GSO towards CLT, GSO either can't see me, or gets an
incorrect mode C for a short period of time. Can't see why one or the
other. Can't see why there is an anomoly at all. On the other hand, I flew
RDU towards CLT practically every week for 3 or 4 years. GSO never had a
problem seeing me on that route. Just one of those things that awaits
migration to better technology.