"Ron Natalie" wrote

I've never seen a hand held transponder since Terra went out of business.
They used to make a balloon pack (essentially the TRT250
and a battery) as you suggest.

I was never sure of the legality of this especially once you get
to the point of needing mode C (which the Terra didn't address,
mind you back in the day, unless you were very high or near one
of the busier TCA's you didn't need mode C).

I doubt that it would be legal as mode C, unless it was a hard installation,
and properly set up, blessed, pontified, and so forth. You could still go
to the effort to get it approved; but nobody has to know that you are not
going run it all of the time.
--
Jim in NC