This sounds more like poor engineering than any actual design goal.
Any HT I have used will happily transmit into a large mismatch with no adverse affects.The fact that this is a 10W HT would lead me to believe that it is probably operating on the fringes of capacity anyhow, and probably hard pushed to dissipate all that heat, even in a perfectly matched situation.
I don't think you'll be able to measure the impedance of the transmit path in place. If you had schematics you could calculate it though.
/ Gerry
