If your TV picture is breaking up or pixelating then you probably are experiencing a weak signal or signal interference.
Check all of the connections from the wall to your cable box and from the cable box to your TV to ensure that all connections are tight.
Common causes are faulty antenna cabling and connections, bad atmospheric conditions, or electrical appliances operating in the area. The most common solution is to retune the TV, but if that doesn't help you will need to call an antenna technician.
For more information, check out the following article: How can I fix reception issues with my digital TV?