LOST COM PROC; CODE 7600; AND PRIORITY HANDLING INITIATED BY THE FLC OF A B737-300 WHEN THEY HAVE INTERMITTENT LOSS OF COM FREQ WITH CTR CTLR AT ZOA; CA.

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AT FL310 WE NOTICED WE HAD NOT HEARD ANY RADIO CHATTER FOR SEVERAL MINS. SINCE WE WERE APCHING TOP OF DSCNT WE ATTEMPTED COM WITH ZOA. AFTER SEVERAL CALLS WITH NO ACKNOWLEDGEMENT NOR RECEPTION OF OTHER ACFT WE SUSPECTED RADIO FAILURE. EXTENSIVE TROUBLESHOOTING OF BOTH RADIOS; MIKES; CIRCUIT BREAKERS; AND HEADSETS WAS CONDUCTED WITH STILL NO COMS WITH OUTSIDE WORLD AT ALL. WE EVEN SUSPECTED STUCK MIKE; BUT EVENTUALLY RULED IT OUT. SEVERAL MINS LATER; COMS WERE REESTABLISHED. NORMAL DSCNT WAS INITIATED AND EQUIP CHKS WERE CONDUCTED. ALL RADIOS AND EQUIP APPEARED TO OPERATE NORMAL. WE SUSPECTED CAUSE WAS THOSE NASTY STRAY 'TRONS.' ONCE ESTABLISHED DIRECT INTXN GILRO AND LEVEL 9000 FT; ZOA GAVE US A VECTOR 25 DEGS R FOR TFC. THAT WAS THE LAST RADIO COM WE HEARD FOR THE NEXT 7-9 MINS. SUSPECTING MULTIPLE RADIO FAILURE AGAIN; WE CONDUCTED TROUBLESHOOTING WITH NO SATISFACTION. SINCE WE WERE WELL R OF COURSE AND APPROX 25 MI FROM FIELD WE ELECTED TO SQUAWK 7600 AND XMIT IN THE BLIND OUR INTENTION TO TURN DIRECT TO SJC FIELD. A COUPLE OF MINS LATER; COMS WERE REESTABLISHED. ZOA SWITCHED US TO BAY APCH CTL. WE ASKED FOR CLRNC TO LAND EARLY SHOULD THE RADIOS FAIL AGAIN. BAY APCH CTL CLRED US FOR VISUAL RWY 30R AND LNDG. THEY ALSO ASKED IF WE WERE 'OPS NORMAL' IN THE COCKPIT. WE AFFIRMED THAT WE WERE. LNDG AND TAXI WENT NORMAL. DISPATCH AND MAINT WERE CALLED ONCE PARKED. TWR ASKED US TO CALL BAY APCH CTL WHEN ABLE. THE BAY APCH MGR DID NOT UNDERSTAND WHY WE 'STRAYED' OFF COURSE RATHER THAN INTERCEPTING VOR INBOUND TO SJC. AFTER EXPLAINING OUR SEQUENCE OF EVENTS; HE THEN UNDERSTOOD IT WAS ZOA THAT GAVE US THE VECTOR 25 DEGS R FOR TFC BEFORE WE LOST ALL COMS. HE HAD BECOME VERY CONCERNED OF A POSSIBLE HIJACKING. WE ENDED CONVERSATION AGREEING THAT ALL APPROPRIATE PROCS HAD BEEN FOLLOWED ON BOTH HIS PART AND OURS.