Many rigs have the Winegard Batwing antenna. Look to see if you have a power supply small button on an antenna wall plate. This puts 12 volts DC onto the coaxial cable to power a booster inside the head. If there is no noticeable different in picture quality, the head could be bad or coaxial cable is corroded at connections.
Older Batwings would need the add on Digital antenna to get the newer digital signals.
You are going to have issues with older TVs as some are not able to get the new digital signal. That would mean replacement time!