What was found
PILOT REPORTED INOPERATIVE NAV/LOCALIZER ON 109.50 MHZ AND A LOUD SQUEAL IN AUDIO. PROBLEM WAS PECULIAR TO THAT FREQUENCY AND DID NOT APPEAR IN OTHER NAV RADIO. DETERMINED PROBLEM TO BE IN THE UNIT AND NOT IN THE AIRCRAFT. TESTED 3 OTHER KNS-80'S AND ALL DISPLAYED SAME PROBLEM, ALTHOUGH IT WAS NOT BAD ENOUGH TO DEGRADE THE NAV PERFORMANCE. CONSULTED THE MANUFACTURER. MFG AWARE OF THE PROBLEM AND HAVE A FIX FOR IT. CONTACT LOCAL BENDIX/KING DEALER OR ALLIED SIGNAL FOR FURTHER INFORMATION. SUBMITTER RECOMMENDS MFG RELEASE A SB AS SOON AS POSSIBLE. COULD BE A PROBLEM IN IMC.