RJ,
I had the same problem till I upgraded to satellite tv, 90% of the channels have good to excellent signal, roughly 10% are ok to good, HD on the other hand is excellent throughout with a few channels being exceptionally superior (Discovery Theather, ESPN, MusicHD, and a few more.) Most channels are now offered in HD, this will make a huge difference in your PQ. Don't get discouraged, just experiment.