In article ,
Rob McDonald wrote:

Nathan Young wrote in
:

On Sun, 02 May 2004 17:34:05 -0400, Bob wrote:

Is it possible that some oil on the transponder antenna would cause it
to transmit intermittently?
...

Probably not...

It certainly seems to make a difference on the 172 I fly right now (a
rental). We are out in the boonies so the transponder isn't usually needed,
and the oil accumulates. When people don't clean the antenna before
venturing into civilization controllers comment that they are not getting
our altitude information. I've tried it both ways (unintentionally) and
confirmed this.

Rob

A friend had the same problem on his 182. I suggested that he switch the
Txp to the DME antenna and vice-versa, as they are identical. He
stopped having Txp problems.