If there is a local VHF FM station on 97.3MHz this could cause problems to some radios having a Local Oscillator Frequency 0f 10.7MHz. If memory serves its called Second Channel interference...97.3Mhz might just be a local commercial station...
As I recall Rockwell -Collins VHF-20's were particularly susceptible to this problem and is the principle reason why FM Immunity mods were introduced to some VHF Nav receivers...