Tim, it's neither. When someone uses the handheld on the ground when
I'm flying in my glider, the transmission is very weak. So much so
that I have to close all the vents and turn up the volume considerably
to hear what they are saying. The radio operates just fine; it's just
that it doesn't seem to transmit well.
I'm only guessing, but I'd put my money on the antenna as the problem.