HDG TRACK POS DEV DURING IAP ILS APCH. POSSIBLE EMI NAV RADIO INTERFERENCE.

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DURING INITIAL PORTION OF ILS APCH TO RWY 36L AT CVG ON A HDG OF APPROX 005 DEGS WITH CDI CTRED. WE NOTED AN ACFT ON APCH TO RWY 36R (700 FT HIGHER) TO BE CLOSER THAN NORMAL. WITHIN SECONDS; WE RECEIVED A TA; LOC COURSE APCHING 2 DOTS L; AND APCH CTL GIVING US A VECTOR OF 350 DEGS TO REINTERCEPT. WE WERE LEVEL AT 2500 FT MSL WITH THE GS; APPROX 1 1/2 DOTS ABOVE (AND COMING DOWN. WE CONFIGURED AND FLEW APCH WITH SLIGHT CORRECTION TO MAINTAIN COURSE AND GS (LOC HAD BEEN POSITIVELY IDENTED PRIOR TO COURSE INTERCEPT). WHEN WE BROKE OUT AT APPROX 600 FT WITH LOC AND GS CTRED. WE APPEARED SLIGHTLY HIGH; THEN NOTED ERRATIC CDI AND GS SHOWED US 2 DOTS HIGH. WE WERE IN A SAFE POS TO LAND AND QUERIED THE TWR IF THE LOC WAS MONITORING. AFTER TAXI-IN; GND TOLD US NEXT 2 ACFT ON APCH TO RWY 36L WERE NORMAL WE ASKED FLT ATTENDANTS IF ANYONE WAS USING A COMPUTER. ONE FLT ATTENDANT SAID SHE ASKED A PERSON TO TURN OFF A GAME COMPUTER DURING THE APCH. DURING TAXIING HE CLAIMED HE TURNED IT OFF. WE MADE A WRITE-UP IN THE LOGBOOK. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR WAS ASKED IF HE HAD WRITTEN UP THE NAV RADIO PROBLEM IN THE LOGBOOK AND HAD HE FOLLOWED UP ON THE MAINT 'FIX.' THE REPLY WAS IN THE AFFIRMATIVE. MAINT HAD CHKED THE RADIOS AND FOUND THEM ERROR FREE. RPTR STILL FEELS THAT THE PAX WAS WORKING THE GAME OR COMPUTER AS THE CABIN ATTENDANT SAW HIS FINGERS 'WORKING THE KEYS' WHEN HE SAID HE HADN'T BEEN USING IT. RPTR STATED; IN REPLY TO THE RELATIVE QUESTION; THAT THE GS RECEIVER ANTENNA IS HALF WAY UP THE VERT STABILIZER ON THE 727. HE STILL FEELS THAT THIS WAS AN 'EMI' EVENT. SUPPLEMENTAL INFO FROM ACN 282127: 1 OF OUR FLT ATTENDANTS IN THE BACK SAID A PAX HAD BEEN USING A COMPUTER; BUT HE DENIED IT WAS ON DURING APCH.