A B727-200 CREW; ON INTERCEPT HDG FOR AN ILS TO ATL; EXPERIENCED IRREGULAR LOC DEFLECTIONS ON THE CAPT'S CDI; RESULTING IN A CORRECTIVE VECTOR FROM ATC.

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APCHING ATL FROM SW TOLD TO EXPECT RWY 27L. SUBSEQUENTLY CHANGED AND GIVEN ILS RWY 26R. NUMEROUS DEVS DUE TO TSTMS IN LCL AREA. APCH GAVE TURN TO 240 DEGS TO INTERCEPT LOC TO RWY 26R. CAPT PF NOTED IRREGULAR DEVS ON HIS CDI. FO LATE SWITCHING TO NEW LOC FREQ DUE TO USING WX RADAR. CAPT COMMANDED ON CDI DEVS AS FO SWITCHING TO LOC. CAPT'S CDI WENT TO FULL R DEFLECTION AND CAPT STARTED R TURN TO GO BACK. INTERCEPT VERIFIED BY FO'S CDI. AT THAT TIME; ATC DIRECTED FLT TURN TO 180 DEGS AND MAINTAIN 4500 FT DUE TO PASSING THROUGH LOC. SUBSEQUENT APCH WAS NORMAL. AFTER FLT; FLT ATTENDANT RPTED THAT ON APCH; A CELL PHONE WAS RINGING IN THE CABIN AND PAX ANSWERED CALL. SHE WAS UNABLE TO LOCATE WHICH PAX. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: WHILE ON THE INTERCEPT HDG; RPTR'S LOC NEEDLE SEEMED ERRATIC; LEADING HIM TO BELIEVE SOMETHING WAS WRONG WITH HIS RECEIVER. BY THE TIME THE FO'S ILS WAS TUNED IN; THEY HAD GONE THROUGH THE LOC. AT THAT POINT ATC; DUE TO THE WX AND THE HVY VOLUME OF TFC; ISSUED A GAR. NO FURTHER INFO REGARDING POSSIBLE CELL PHONE INTERFERENCE WAS FORTHCOMING.