ELECTRONIC INTERFERENCE TO ONBOARD NAV INSTS.

Narrative

TRACKING INBOUND ON THE 234 DEG RADIAL OF IAH VOR; BOTH CAPT AND FO VOR CDI'S WERE SCALLOPING BADLY EITHER SIDE OF CTR POS. THERE WERE NUMEROUS TSTMS IN AREA AND WE ASSUMED ELECTRICAL INTERFERENCE. APCH CTL WAS SO BUSY; THAT WE COULD NOT CONTACT THEM TO ADVISE OF THE PROB. AT APPROX 30 MI SW OF IAH; APCH CTL ADVISED US THAT HE SHOWED US 4 MI N OF COURSE AND IN THE SAME BREATH GAVE US ANOTHER FREQ. THE NEXT CTLR ON INITIAL CONTACT ADVISED US TO TURN TO A 030 DEG HDG FOR RADAR VECTORS FOR AN ILS TO RWY 9 APCH. THE CAPT CONTACTED THE FLT ATTENDANT AS SOON AS HE COULD ON THE INTERPHONE AND ASKED HER TO CHK FOR THE USE OF ANY COMPUTER OR LIKE EQUIP BY THE PAX. WITHIN ABOUT 15-30 SECONDS THE COURSE DIRECTOR INDICATORS QUIT SCALLOPING. THE CAPT CHKED AGAIN WITH THE FLT ATTENDANT AND WAS ADVISED THAT A PAX WAS USING A PORTABLE COMPUTER OR SOME SUCH DEVICE. THIS WAS AFTER SHE HAD MADE AN ANNOUNCEMENT TO TURN ALL SUCH DEVICES OFF! THE PAX STOPPED USING THE PORTABLE ELECTRONIC DEVICE; THE CDI'S STOPPED SCALLOPING!