I have a Furuno model 1623 Radar. It has worked flawlessly for over 200 hours. About a month ago we were cruising along in the dark and hit a tug boat wake a little hard and the screen went to dark, wide concentric bands with a dark center, very similar to a target. The next day, I pulled the radome lid. There is a little string that is attached to the radome that I though may have snagged the rotating antenna. Trashed the string, fired it up and the the radar worked fine. A week ago, I was cruising along slowly in light fog and hit a tour boat wake and the the screen did the same. The only thing I found in the radome later on was light condensation on the inside of the lid. A trouble code "No heading pulse" comes up on the screen. This is supposed to indicate antenna cable problems per the manual. System trouble shoot indicates ok. The antenna turns but will eventually make a catching sound and stop. The belt acts as if it is binding up a little but I can't imagine there is enough tension to stop the rotation. When I give it a little push, it starts up again and gives a fine picture. I talked to Furuno and they thought maybe the unit should be sent in for a newer, larger motor. It seems to me that the problem should be simple due to its acute onset but I can't seem to narrow it down. There was a point where it ran longer after I tightened the ground screw and I thought I had it licked. I went through all other connections and ended up getting a much stronger sounding motor but still get the binding up noise followed by eventual stop of the antenna. Any input would be appreciated. Thanks.