Mmmmmm kaaaay now what ^%#$%$ CB

Disconnect the coax from the back of the radio. If it goes away it's probably RFI (radio frequency interference). This can be tough to eliminate.

If it does go away, you need to locate the source(s). It can be creeping in via the Antenna, coax or both. My current setup will pick up RFI from other vehichle electrical systems passing buy...

To find the source, re-connect the coax and remove the antenna and check it. If it's still as loud as it was, it's probably the coax (poor shielding), if it lessens but is still present, it's probably a combination of antenna and coax.

You may be able to reduce the interference with an RFI Choke (google it).

If removing the coax doesn't improve the interference than you've probably got a ground loop somewhere. Hooking your radio directly to the batter is typically the best solution, but doesn't always eliminate the problem. Your battery connects to your frame where other items are also grounded, increasing the potential for ground loops. Trying different grounding locations for the radio may help. Keep the power directly to the battery and look for the absolute shortest distance from the radio to a good metal source and see if it helps... not garunteed but things to explore.

 

its a grounding issue. you need to run flat braid ground straps on everything. Cab, frame, doors, everything. this will help immensely with interference.

 

Start with grounding the antenna and then the radio itself.
Then work your way back to the battery box,
door to cab
cab to frame
frame to battery box
battery to battery box
Fresh charged drill motor and a handful of terminal connectors,12 ga wire and
about a dozen 5/16 self tapping screws

Use a round terminal connector and some 12ga wire,go from the radio mount screw across to your A pillar(behind the plastic there is steel)
example:
If you have a grab handle use a connector thats big enough for the bolt,use duct tape to hold the connector while you reinstall the plastic cover and handle.

There is only so much you can do,these new style trucks and their multiple ECM's
are always going to cause RF feedback.