AN H25A CREW; ON APCH TO PVD; UNABLE TO CONTACT THE TWR VIA VHF COMS WERE ISSUED A GREEN LIGHT CLRING THEM TO LAND.

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WE HAD EXPERIENCED AN 'ALT HOLD' AUTOPLT PROB EARLIER IN THE FLT AND WERE WATCHING THE AUTOPLT CLOSELY. AFTER CLRED FOR ILS WE TRIED CONTACTING TWR WITH NO REPLY. RECEIVED A GREEN LIGHT AND LANDED. GND SAID THEY NEVER HEARD US AND WE COULD ONLY HEAR THEM WITH THE SQUELCH ON. AT CRUISE WE HAD NOTICED SOME PROB RECEIVING CENTER; BUT WE WERE ABLE TO HEAR OTHER ACFT SO WE THOUGHT IT WAS CENTER'S TRANSMITTER. THAT NIGHT WHEN UNPACKING I NOTICED A HIGHWAY TOLL TRANSCEIVER; ON; IN MY BAG. I REMOVED THE BATTERIES. NEXT DAY WE HAD NO PROBS WITH EITHER RADIO. IT IS VERY POSSIBLE WE HAD INTERFERENCE FROM A PORTABLE ELECTRONIC DEVICE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: IN CONVERSATION WITH THE RPTR IT WAS REVEALED THAT; THE 'HIGHWAY TOLL TRANSCEIVER' WAS LOCATED IN THE FORWARD BAG COMPARTMENT; ADJACENT TO THE AVIONICS BAY. FORTUNATELY ALL INTERFERENCE STOPPED; WITH NORMAL VHF OP; ONCE THE BATTERIES WERE REMOVED FROM THE TRANSCEIVER. THE ACFT HAS BEEN FLOWN ON SUBSEQUENT FLTS WITH NO REOCCURRENCE OF THE PROB.