wrote:
Looking back, the 296 probably pooped out when the
transponder went on in the runup area.

On the trip back, there was no problem on either portable unit when the
transponder was turned on.

Has anybody ever seen the 296 (or their own portable) act like this??

On a couple of occasions I've had a Garmin portable (a GPS III Pilot first,
later a 296) "flatline" due to interference from a Cessna NAV-Com, but only
during transmission. Both times I swapped out the radio and that fixed the
problem.
--
Dan
C-172RG at BFM