They seem to be pretty resilient. I have mine mounted on the dash of my Toyota SUV (there is really no other place to mount it) and it gets cooking hot on sunny days. Even then I can still talk on it and it works fine. Power output seems to stay the same no matter the temperature.
I mostly use my mobile to communicate with my house when I'm out and about (our island has only marginal cell coverage). I run it in FM mode at full power into a 3 foot firestick on the front left fender.
The 6666's FM performance is actually very impressive. Using a Q5N2 at home into an A-99 at 40' I can talk to the girlfriend when she's out in the car pretty much anywhere within about a 25 mile radius, and in certain directions up to about 35 miles.
I've done a fair amount of testing and can report that FM mode works FAR better than AM, which is rough and static laden at about 15 miles while the FM is still almost full quieting.
On top of that the Anytone's auto squelch really works well in FM mode. I can drive around all day and not hear any static at all. none. Notorious spots with bad powerline static don't even trigger it. Yet weak signals still make it through fine. It's so much better than the old days where you had to ride with the squelch at 3/4 to stop the constant static blasts !
Edit to add: I do wish the auto squelch would work on SSB as well as AM and FM. Not sure why they limited it to those modes but I'm guessing it may need an actual carrier signal to work.
