On Nov 25, 12:41*am, Dave wrote:

That 125 foot difference can be important. you may be indicating 2990
feet while your transponder is reporting 3100 feet. If the class B
airspace starts at 3000, then you may be validation of busting class B
and be totally legal.

Dave, this was my precise reason for shutting the Xponder down
especially thinking ahead for the return trip home.

KMBO is under the floor of KJAN charlie airspace and I was concerned
that if we flew at 1500, ATC would see us at 2200. In my mind, no
information is better then wrong information with what cards were
dealt to me even if I wasn't PIC.