ACFT TYPE DEMONSTRATES A RADIO COM PROBLEM BECAUSE OF AUDITORY INTERFERENCE. FLC CHANGES FREQ WITHOUT CLRNC.

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WAS ON A VOR/DME APCH TO ARPT. SWITCHED TWR AFTER DIRECTED BY APCH. TWR FREQ IS 120.0. THE TWR CLRED US TO LAND; BUT 120.0 WAS VERY BROKEN AND GARBLED. THIS ALWAYS HAPPENS ON THE MLG MODEL ON 120.0 OR FREQS ENDING IN '.0.' TWR BECAME VERY UNREADABLE SO IN INTEREST OF SAFETY AND COMS; WE SWITCHED TO GND CTL; 121.9; TO REESTABLISH COM. AT THIS TIME WE WERE 500 FT AGL PREPARING TO LAND. GND CTL CAME BACK AND SEEMED UPSET THAT WE SWITCHED WITHOUT PERMISSION OR TELLING THEM. I HAVE BEEN TO THIS ARPT BEFORE AND HAVE HAD TO USE GND CTL TO TKOF AND LAND. THIS HAS BEEN A PROBLEM IN OUR MLG MODEL FOR YRS AND NOTHING HAS BEEN DONE ABOUT THE TWR FREQS OR THE ACFT. SUPPLEMENTAL INFORMATION FROM ACN 208757: THE 'POINT 0' FREQ HUM IS A KNOWN MLG MODEL COMS PROBLEM. THIS PROBLEM SHOULD BE RECTIFIED AS SOON AS POSSIBLE. EITHER THE FAA SHOULD NOT USE IT OR THEY SHOULD COMPEL THE MANUFACTURERS TO CORRECT THE PROBLEM. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: RPTR SAID HIS ACR WAS WORKING ON A FIX AND HAD ALSO ISSUED A BULLETIN TO ALL PLTS ABOUT THIS INTERFERENCE PROBLEM ON COM FREQ 120.0 MHZ. RSW TWR IS FAMILIAR WITH THE PROBLEM BECAUSE; IN THE PAST; IF A PLT COMPLAINED ABOUT THE PROBLEM; THE TWR ASKED IF THEY WERE FLYING THAT PARTICULAR MODEL MLG. HE IS NOT SURE IF THE RPTED INCIDENT WAS DUE TO THE FIX NOT BEING INSTALLED YET OR IF AN INSTALLED FIX FAILED TO WORK. COINCIDENTALLY; THE RPTR HAS A PERSONAL SMA AND HAS THE SAME PROBLEM WITH 120.0. HE SAID A LORAN INSTALLATION ON HIS ACFT INTERFERES WITH HIS RECEIVER. A CALLBACK TO THE CAPT DISCLOSED THERE IS NO HISTORY OF THIS PROBLEM WITH THE OLDER MODEL ACFT BUT THAT WHEN THEY WERE CONVERTED TO THE NEW ADVANCED ELECTRONICS; THE PROBLEM AROSE. HE SPECIFIED THAT THE PROBLEM HAS HAPPENED ON 118.0; 120.0; AND 123.0 MHZ.