Batboard

I have a 2013 Camero patrol car with a CDM1550 head mounted on the console in front of the shifter and the radio mounted in the trunk on the driver's side. The antenna is a 5/8 Larsen on the passenger side rear fender. The hood is plastic and the battery is mounted in the spare tire well in the trunk. There is a low pitched rumble, that changes with motor speed, on the transmitted signal. It is nothing like alternator whine. I hooked-up a CM300 in the trunk and signal was clean. I installed a power line noise filter and it helped just a very little on the CDM. All radio power comes from trunk mounted battery. There is no good place to mount a complete CDM or CM in the front of the car. Does anyone experience?

Pop the trunk mnt CDM out of it's bracket to see if it still does it. If the noise stops, then you have a ground loop, and need to isolate the bracket. If it does not, then you may have rf getting into the ctrl cable which you may be able to reduce with clamp on ferrite beads.

Bill_G wrote:Pop the trunk mnt CDM out of it's bracket to see if it still does it. If the noise stops, then you have a ground loop, and need to isolate the bracket. If it does not, then you may have rf getting into the ctrl cable which you may be able to reduce with clamp on ferrite beads.

To add on what bill has mentioned, keep the antenna cable away from the control cable. Don't tie wrap them together to make things neat. Don't coil up the extra coax cable with the control cable. Do that in a different location away from the radio.

Jim