Batboard

My FD received a 2013 Freighliner M2-106 fire engine. The factory installed 2 VHF CDM1550 LS + and I programmed them. Since delivery, we have had a constant issue of being able to transmit to dispatch and be heard well, but all we get in return is static with occasional voices heard in the static. Some days there's nothing at all. I have been trying to figure this out and I am at a loss. I D/C'd all of the accessories (sigtronics, speakers, etc) and tried to do a remote mount with the unit away from the center console with no change. I have ruled out the programming as the issue as well. The antennas are a standard one I buy by the dozen, and I have swapped them with other rigs with no change. I even scratched the paint away on top of the cab to make sure the antenna contacted the body for grounding. The builder used aluminum coax that runs up the B posts to the roof. All of that said, anyone have any ideas? I have never come across this issue before.

Call your radio shop. Make sure the rcvrs actually work. And put a wattmeter on the antennas. Both of them might have bad lines or connectors.