Can you rotate the direction of "digital" antenna on your Vista or is it one of the flying saucer shaped stationary so called "omni-directional" antennas? Digital broadcast signals are directional and I have yet to try an "omni-directional" antenna that did not have to be directed toward the signal source. This is why your picture breaks up or is there on one scan and not the next - the direction toward the signals is off. If you can direct the antenna toward the signal you will lock in these signals - with a picture that breaks up just a slight turn in one direction or the other will lock in that signal solid. '