Read and understand about , REAL Digital Broadcast Tv Channels , Virtual Digital Broadcast Tv Channels , Analog Broadcast Tv Channels ,
http://forum.tvfool.com/showthread.php?t=695. Also here is how to aim Tv antennas ,
http://www.kyes.com/antenna/pointing/pointing.html. Also you can call the Tv stations that you are not receiving and talk with the engineering department , ask all kinds of questions , here are some , has there been any changes to the transmitted power?? Has the beam tilt of transmitter antennas been changed so the signal does not go out as far?? Has the pattern of the transmitted signal been changed so that I would be less likley to receive at my location?? Ask the engineering department what they think about the non reception at your location. The reception problems might due to interference.