A LEAR 35 PLT RPTS LOSS OF GPS NAV NEAR NAPLES; ITALY.

Narrative

I AM RECENTLY BASED AT CAPODICHINO ARPT; NAPLES; ITALY; FLYING LEAR 35'S. BETWEEN THE DATES OF NOV/XA/99 AND DEC/XB/99; I CONSISTENTLY LOST GPS NAV FUNCTION WHEN RETURNING TO NAPLES. WHEN APPROACHING FROM THE N; THIS LOSS OCCURS SE OF THE TEANO VOR (TEA) TO THE INTERCEPTION OF THE RWY 24 LOC; BENTO INTERSECTION; AND TO ABOUT POMIGLIANO VOR (POM). WHEN APPROACHING FROM THE S; THIS OCCURS BETWEEN THE SORRENTO VOR (SOR); AND THE GALTI; EKTOL; AND BENTO INTERSECTIONS; AND THEN ALONG THE RWY 24 LOC TO THE AREA OF THE POMILGLIANO VOR (POM). THIS OCCURS IN TWO DIFFERENT ACFT; BOTH LEAR 35'S; USING TWO TYPES OF GPS RECEIVERS; BOTH IFR APPROVED FOR ENROUTE AND NON-PRECISION APPROACHES. THESE AREA TRIMBLE AND APOLLO RECEIVERS. I SUSPECT THAT HARMONIC SIGNALS FROM ITALIAN TV TRANSMITTERS ARE THE CAUSE OF THIS LOSS OF GPS. THIS LOSS TYPICALLY OCCURS WHEN USING THE GPS TO POS THE ACFT FOR THE ILS RWY 24 APCH TO NAPLES. THIS THEN REQUIRES A REQUEST FOR VECTORS FROM NAPLES APCH WHEN THE LOSS OCCURS. THIS SIT SHOULD BE NOTAMED AND MENTIONED ON BOTH THE DOD AND COMMERCIAL CHARTS; AND THE APPROPRIATE FLIP SUPPLEMENT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR CONFIRMED THAT THEIR LEAR 35 ACFT (3) ARE EXPERIENCING THE GPS NAV FUNCTION LOSS. THIS LOSS OCCURS ONLY AT THE NAPLES ARPT AND ONLY AT ALTS BELOW 15000 FT AS THEY APCH THE ARPT. THEY HAVE NO PROB ON DEP SINCE THEY'RE NOT USING THE GPS TO NAVIGATE. RPTR BELIEVES THE TV TRANSMITTERS ARE CAUSING THE PROB BECAUSE THE ITALIAN TV TRANSMITTERS OPERATE AT A FREQ 2 TO 3 HIGHER THAN THEY DO IN THE UNITED STATES.