COM RADIO FREQS IN A HIGH TECH LGT CHANGE SPONTANEOUSLY CAUSING LOSS OF RADIO CONTACT WITH ATC. SOMETIMES THE FREQ DISPLAY CHANGES IN CONJUNCTION WITH THE FREQ CHANGE AND SOMETIMES THE FREQ DISPLAY DOES NOT CHANGE AS THE FREQ CHANGES.

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WHILE ENRTE ON VECTORS FROM ZDC WE WERE CALLED FROM COMPANY RADIO TO CONTACT ZDC. THE FREQ GIVEN US WAS THE FREQ SET ON OUR RADIO. WE RECHANNELED THE RADIO AND ESTABLISHED CONTACT. WE WERE TOLD THEY HAD BEEN CALLING FOR 100 NM. WE NEVER HEARD A CALL! ON APCH WITH EWR APCH AGAIN ON VECTORS; WE HEARD THE MALE CTLR TURN INTO A FEMALE. THINK THERE HAD BEEN A CTLR CHANGE! WE CONTINUED FOR SOME TIME LISTENING TO CONSTANT TFC CTLING. WE HAD CROSSED THE LOC AND WERE 15 OR SO MI THROUGH THE LOC WHEN WE ASKED 'WHAT'S THE PLAN FOR US?' WE WERE MET WITH WHO ARE YOU; WHERE ARE YOU; YOU ARE ON THE WRONG FREQ! AGAIN LOST COM. WE RE-ESTABLISHED COM WITH EWR APCH AND WERE VECTORED UNEVENTFULLY. WE FINALLY DISCOVERED THAT OUR RADIO HAD BEEN CHANGING FREQS WITHOUT BEING TOUCHED. THE FIRST TIME THE CORRECT FREQ IN THE WINDOW; THE SECOND THE FREQ IN THE WINDOW WAS DIFFERENT THAN THAT SELECTED ORIGINALLY AND IMMEDIATELY CHANGED 7 DIGITS WHEN BARELY TOUCHED. AND A THIRD TIME WHEN GND WAS PRE-SELECTED PRIOR TO LNDG AND HAD CHANGED FROM 121.8 TO 131.8. THESE WERE DUAL HEAL TYPE RADIO. SUPPLEMENTAL INFO FROM ACN 207782. WE WERE TURNED TO A HDG OFF THE AIRWAY FOR TFC. AFTER APPROX 5 MIN WE GET A SELCAL AND ARE TOLD TO CONTACT WASHINGTON CTR ON 2 DIFFERENT FREQS; ONE BY ATLANTA RADIO AND ONE BY ANOTHER COMPANY FLT. WE WENT BACK TO THE PREVIOUS FREQ AND ASKED THE CTLR FOR A CORRECT FREQ AND HE SENT US BACK TO THE ONE WE WERE JUST ON. THE RADIO HAD AUTOMATICALLY CHANNELIZED WITHOUT OUR KNOWING IT AND NO CHANGE OF FREQ SHOWING ON THE CTL HEAD. TO OUR KNOWLEDGE THERE HAD BEEN NO TFC CONFLICT. THIS SITUATION WAS VERY INSIDIOUS BUT BETTER SITUATIONAL AWARENESS MIGHT HAVE RESOLVED THE PROBLEM SOONER. ON DIGITAL RADIO CTL HEADS BE AWARE THEY RECHANNELIZE WITH NO COCKPIT INDICATIONS.