There is no real reason to bench check then check it in the airplane
except to verify the transponder works prior to a new installation or if
it is a mode "s" transponder, he may only have bench equipment to test it.
A bad antenna or antenna connection can swing a transponders frequency
out of range to pass the test.
He may be trying to get a baseline to validate the installation.
If he isn't charging more for the bench check and it's not a mode "s" go
for it. If he is charging lots more and your confident that the
installation is sound, make a few more calls.

Since your static system is new, it should be checked for leaks. That
can be done by an A&P, manufacturer or the guy who does your transponder
check.

You as the manufacutrer of the aircraft who installed the transponder
can also test and inspect the transponder installation, but it still
needs to comply with appendix f.

dave


Thanks for all the extra info Dave. I talked to my preferred avionics shop
today, the one who said they wouldn't come to my airport. When he really
understook that I couldn't bring the plane to him, he agreed to come over
next week to do a "functional test". He's the one that tested my RV-8 a
year or so ago, so I'm pretty happy that he's agreed to do this. I think
I'm all set now.

Thanks again,
Rusty