I have a rooftop antenna for OTA. The two towers that my stations come off of are 45 degrees apart so I aim right between them and they are about 10 and 15 miles away. I get around 90% or above on all the stations. The last few days I've been having trouble with channel 27 ABC in Madison WI. The meter says that I'm at 90%, but I'm getting terrible blocking and pixelating and sometimes the top and bottom half of the picture don't match up. Any ideas what is causing this and what I can do. By the way it is happening on both my 622 receivers on worse than the other.