I confess that I know very little about radios. I also believe that the USA still uses the CB bands. The UHF 40 channel system is used by everybody all over Australia with very little CB still used. So any suggestions from me are worth what you pay for them! If you have switched off or disconnected every thing else except the radio and still get the feedback then it is the radio and one of it's components that is possibly causing the problem. Does it occur over all channels or just around the channel you useIJ Try a different radio on your aerial system. A weird one which has occurred [very rarely] is that a part of a machine's electrical circuitry has become tuned to the frequency of a powerful local transmitter and then reradiates at a different lot of frequencies, in this case maybe yours! A completely different situation but as an old glider pilot, I actually received some radiation burns to my hand when about a half of a mile of winch wire, which is used to launch gliders a little like a kite on a string, became a huge aerial, tuned to the frequency of a close commercial radio transmitter tower, while I was being launched in the glider. The resulting powerful jolt made my eyes very watery and definitely got my undivided attention. It does happen. The reality is that your problem is probably something very simple. Finding it is the problem.The best of luck!