RADAR LOSS AND INTERMITTENT TARGETS OCCUR SINCE ASR-9 WAS INSTALLED.

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TPA RADAR SYS OPERATING ON BEACON ONLY DURING ASR 9 INSTALLATION. ACFT HAS GOOD BEACON TARGET WITH ZMA. ACFT ENTERS TPA AIRSPACE AND BEGINS TO SHOW A WEAK BEACON TARGET. RADAR CONTACT IS LOST AT 4000 FT 20 SE OF TPA; AND DOES NOT RETURN TO A GOOD BEACON TARGET UNTIL 10 SE OF TPA. PLT RPTED NO OTHER PROBS WITH XPONDER. I SOLICITED THE PLT TO CANCEL IFR; AND HE CONCURRED. TPA BEACON SYS HAS BEEN UNRELIABLE ON A CONTINUING BASIS FOR THE YR I HAVE BEE AT TPA. THE RADAR SYS IS SUBSTANDARD TO THE OTHER SYS I HAVE WORKED; WHICH INCLUDE STL; SDF; AND IAD. ACFT OFTEN COAST AND ARE TOLD THEIR XPONDERS ARE INOP WHEN THEY HAVE NOT HAD OTHER PROBS ON THEIR ENTIRE RTE OF FLT. ON NOV/XX/93; I WORKED AN SMT X AT 7000 FT MSL ON V-157 SBOUND TO LAL THEN DIRECT SRQ. HIS MODE C BECAME INOP 25 NM N OF LAL AND DID NOT SHOW MODE C AGAIN UNTIL 15-20 NM WSW OF LAL. I CALLED ZJX TO VERIFY THAT THEY WERE SHOWING A STRONG BEACON AND MODE C ON THE ACFT. THEY SHOWED THE ACFT AT 7000 WHILE I HAD NO MODE C AT ALL. AIRWAYS FACILITIES WAS ADVISED AT TPA; HOWEVER; I BELIEVE NO ACTION WAS TAKEN. THIS CONTINUING PROB OF UNRELIABLE OR NO MODE C OR ERRONEOUS MODE C IS A HAZARD TO SAFETY AT TPA.