AN AIRBUS 320 ON APCH AT 9 MILES BTWN 8000 FT TO 6000 FT LOCALIZER SIGNAL OSCILLATED FROM STOP TO STOP WITH AUTOPLT MAKING 20 DEG DEVIATIONS. CAUSED BY PAX ELECTRONIC DEVICE.

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DURING APCH TO SAN LOC OSCILLATED EXCESSIVELY AT ABOUT 8000-6000 FT. AFTER LNDG; IT WAS DETERMINED THAT A PAX HAD TURNED ON A PDA IN DEFIANCE OF OUR FA REQUEST TO STOW THE SAME. THIS PAX ALSO SAID THAT HE DID NOT HAVE TO TURN IT OFF AND PRESENTED AN ARTICLE FROM A PAPER DATED AUGUST 2002 STATING YOU CAN USE PDA ON JETS. THIS WAS HIS REASON AND HE HAD SEVERAL COPIES OF THIS ARTICLE AND WAS WAITING FOR THE FA TO TELL HIM TO TURN IT OFF. THE PAX SAT IN XO AND IS A FREQUENT FLYER. I WAS UNABLE TO TALK TO HIM AS HE LEFT PRIOR TO MY LEAVING THE COCKPIT. I AM ABSOLUTELY POSITIVE THAT THE LOC OSCILLATIONS WERE A RESULT OF THE PDA BEING ON AND STOPPED WHEN THE UNIT WAS TURNED OFF. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR STATED THAT BEING IN A STERILE COCKPIT IN FRONT OF A LOCKED DOOR AND HAVING NO CONTACT WITH THE CAB CREW THE FLT CREW CAN BE UNAWARE OF EVENTS HAPPENING IN THE CAB. THE RPTR SAID THE FIRST HINT OF TROUBLE WAS ON APCH AT 9 MILES 8000 TO 6000 FT WHEN THE AUTOPLT ON LOCALIZER CAPTURE BEGAN TAKING 20 DEG 'HACKS' R AND L OF THE LOCALIZER CENTER. THE RPTR STATED THE AUTOPLT WAS FOLLOWING THE OSCILLATING LOCALIZER NEEDLE WHICH WAS MOVING FROM STOP TO STOP. THE RPTR SAID THE AUTOPLT WAS DISCONNECTED AND THE AIRPLANE WAS MANUALLY FLOWN TO AN UNEVENTFUL LNDG. THE RPTR STATED THAT ON TAXI TO THE GATE THE TWR WAS ADVISED OF THE LOCALIZER PERFORMANCE AND THE TWR RESPONDED THAT NO ALARM WAS RECEIVED AND LOCALIZER OP WAS NORMAL. THE RPTR SAID ON LEAVING THE COCKPIT A CAB RPTED A PAX WHO REFUSED TO TURN OFF A PERSONAL DIGITAL ASSISTANT WHEN ORDERED TO DO SO BY THE CAB. THE RPTR STATED THE PAX JUSTIFIED HIS ACTIONS BY DISPLAYING AN ARTICLE IN USA TODAY DATED AUGUST 20 2002; TITLED 'FAA SAYS YOU CAN USE PDA ON JET'. THE RPTR SAID HE IS ABSOLUTELY CERTAIN THE PDA CAUSED THE LOCALIZER OSCILLATIONS. THE RPTR STATED LOCALIZER SYSTEMS WERE CHECKED BY MAINT AND NO FAULT FOUND.