Buzzed

If you are handy with a soldering iron, I would get a length of rg-58 and use that in to see if that helps. I had the same issue with a motorola speaker and a cobra I bought a while ago and had a spool of rf-173 and used that which elminates the feedback.

 

I have found it is the microphone being to close speaker causes feedback. If you stayed in the drivers seat the mike would still be close to the speaker. Have found that type of feedback to be more of a squeal than a buzz. I do get a buzz when I transmit on cb with the vhf radio on so I just turn off which ever radio I'm not using. When I got the first KW with external speaker mounted by the drivers head I thought it a great idea. Personally for me after trying it out found it annoying.