CAPT OF A B757 FOUND INTERFERENCE WITH ILS LOCATION IDENT AT GUAYAQUIL; FO; DUE TO COMMERCIAL STATION NOISE OVERRIDING THE IDENT CODE WHEN APPROX 29 MI OUT DSNDING. HE BELIEVED THAT HE MAY HAVE TO GO TO HIS ALTERNATE ARPT SINCE THE COURSE INDICATOR NEEDLES SWUNG WIDELY. HOWEVER; ANOTHER ACR ACFT PLT ADVISED THAT IT WOULD CLR UP CLOSER IN; WHICH IT DID; AND A SUCCESSFUL APCH WAS COMPLETED.

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LOCATION: 20 MI N PAL NDB. DURING SETUP FOR ILS AT GYE; LOC IDENT HAD A LCL RADIO STATION COVERING IDENT. NEEDLES WERE ERRATIC AND NO IDENT WAS ABLE TO BE CONFIRMED UNTIL APPROX 5 MI OUTSIDE PAL NDB. POS WAS VERIFIED WITH VOR. THIS HAD AN F4 MESSAGE CONCERNING RELIABILITY BUT WAS IDENT NORMAL AND STEADY. THERE WAS RAIN AT THE STATION AND OTHER ACFT WERE HAVING THE SAME PROB WITH ILS. ALSO; OPS PERSONNEL INFORMED ME THAT OTHER ACR FLTS HAD SAME OCCURRENCE WITHIN LAST 2 WKS WITH DISTANT ALTERNATES AND EL NINO WX AND FULL ACFT IT WAS LIKELY WE WOULD HAVE DIVERTED. WITHOUT INFO FROM ACFT AHEAD STATING THAT THEY WERE ABLE TO IDENT JUST PRIOR TO APCH; UNTIL THIS SIT IS FIXED I RECOMMEND A MESSAGE SAYING THAT THE ILS CANNOT BE IDENTED UNTIL JUST PRIOR TO COMMENCEMENT OF APCH; AND OTHER ADJUSTMENTS ARE MADE IN FLT PLANNING. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT HE HAD FLOWN INTO THIS ARPT MANY TIMES PRIOR AND WAS ABLE TO PICK UP THE IDENT MUCH SOONER; EVEN WITH NO TROUBLE. FOR THIS REASON HE BECAME VERY APPREHENSIVE IN CONTINUING TO START THE APCH WITH THIS PROB. THEREFORE; HE WAS THINKING OF PLANNING TO GO TO AN ALTERNATE WHEN ANOTHER FLC MEMBER OF ANOTHER ACR ACFT VOLUNTEERED THE INFO THAT THE SIGNAL INTERFERENCE WILL GO AWAY CLOSER IN AND THE SIGNAL WILL BE OK. HE CONTINUED ON AND FOUND THE NAVAID DID RESPOND OK AND COMPLETED THE APCH SATISFACTORILY. HE HAS NOT BEEN BACK SINCE HE IS ON ANOTHER SCHEDULE THIS MONTH AND CONSEQUENTLY HAS NOT HEARD OR SEEN ANY MESSAGES ON THIS PROB FROM THE COMPANY. THE COMPANY WOULD ONLY SEND MESSAGES TO THE AFFECTED FLTS.