Almost sounds to me like electrical noise/interference coming from somewhere
nearby. I've had this problem as well. I tried not using the AC adapter that
came with it, that helped somewhat. If I'm running appliances within 20 feet
of my KA-1102 (like the dishwasher, computer, modem, etc.) I hear the
buzzing you're describing.

My Christmas tree's lights made for a nice rhythmic buzz over the holidays.
Had to turn them off each time I wanted to listen to my radio.

I would try taking the radio to an electrically-quiet area (like an empty
beach, hilltop, or somewhere like that) and then see if you can hear these
noises.

Good luck!

Jackie