I have a Uniden UH7700NB 80 channel that's been in storage for 8 years or so. Stored well, in great condition. I recently fitted it the patrol with a new fairly cheapo maxtrac aerial. Can hear chatter but can't talk out. Tried two other UHFs and they behaved exactly the same. Today I returned the cheapo aerial and got a nice 6db GME. Fitted all up and still have the same problem: can hear workers chatting away but can't broadcast to my handheld.
Weird bits:
If I talk on the handheld and scan with car then the car stops one channel past the hand-held and picks up violent screeching that has a hint of my voice.
If I hit the talk button on the handheld, the "signal received" symbol appears on the car but that will happen no matter which channels either are on.

I have gone through the manual and am pretty happy that all settings are where they should be.

Any tips?

.......from under the great down under.