What was found
ATB, UNABLE TO RECEIVE HF RADIO TRANSMISSIONS ON EVERY HF FREQUENCY WE COULD FIND. CONTACTED DISPATCH, ATB REQUIRED. PRIOR TO DEPT HF CHECK WITH OTHER AIRPLANE SUCCESSFUL ON BOTH HF RADIOS. HF LEFT. DEFERRED LEFT HF COM SYSTEM PER MEL 23-11-1-2A-2, PLACARD INSTALLED.