Posted 10/18/2020 07:32 (#8551199 - in reply to #8551078) Subject: RE: Keying two way radio mike kills AM/FM radio
Who installed the mounts? Are you using the factory installed NMO mount, and just screwing an antenna on top of it? Are you using the factory wiring provided next to the antenna connector behind the radio for the radio power? If you answered yes to both of these, I would check to make sure the ground plane mat under the roof (looks like thick aluminum foil) is connected correctly. I would also borrow a SWR bridge / reflected power meter, and hook inline to the radio. A high SWR can start causing weird issues to happen. Also make 100% sure you didn't get a wrong antenna. We once got a VHF antenna that was sold to us as a UHF antenna. They are close in looks, and a 1/4 wave is nearly a 3/4 wave, but it just don't really work right.
If all the above checks good, and you still have issues, it could be a defect on the tractor side. I used to run 110 watt VHF / UHF radios in company rigs. They worked great for years, but one year, the new vehicle had a new style radio that lacked RF shielding. We had the dealer warranty the radio out, and the issue went away.