RDU CTLR ALLEGES CONTINUOUS ASR-9 FALSE TARGET PROBS SINCE 1996.

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WE HAVE HAD A CONTINUOUS PROB WITH 'FALSE TARGETS' BEING DISPLAYED BY THE ASR-9 RADAR AT RDU. THIS HAS BEEN ONGOING SINCE SEPTEMBER OF 1996. IF YOU EXAMINE THE FACILITY OPS LOGS; YOU WILL SEE 'NUMEROUS FALSE TARGETS' HAS BEEN A CONTINUOUSLY CARRIED OVER ITEM. DATA WAS COLLECTED; AND SOME MODIFICATIONS MADE TO THE SYS; BUT NONE OF THESE ACTIONS RESOLVED THE PROB. ANY TIME I ASK ABOUT THE STATUS OF THE PROB; I AM TOLD IT IS A NATIONAL PROB AND THEY CAN DO NOTHING LOCALLY. ON SOME DAYS YOU WILL SEE AS MANY AS 15-20; ALL WITHIN 20 MILES OF THE ARPT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: SUPPLEMENTAL INFO: A TWR SPECIALIST CONFIRMED THIS PROB. FALSE; PRIMARY TARGETS WILL APPEAR AND STAY ON THE RADAR DISPLAY FOR SEVERAL MINS AT A TIME. THE SPECIALIST ADVISED THAT THE FALSE TARGETS SEEM TO GROUP NE AND SW OF THE ARPT; FIVE TO TWENTY MILES OUT FROM THE ARPT; MOST FREQUENTLY GROUPED IN THE VICINITY OF THE APCH AND DEP AREAS FOR RWYS 23 L/R. THE CONDITION EXISTS YEAR AROUND. THE SPECIALIST ADVISED THAT 'FALSE TARGETS' APPEAR WEEKLY ON THE FAC DAILY OPS LOG. THE SPECIALISTS ADVISED OF A RECENT INCIDENT WHEN FALSE TARGETS WERE PRESENT FOR AN 'EXTENDED PERIOD OF TIME' A LONG THE RWY 23R APCH PATH. AN ACR INITIATED AN EVASIVE TCAS RA CLB BECAUSE AN UNIDENTIFIED ACFT TRANSITING THE FINAL APCH COURSE ABEAM THE OM WAS NOT ISSUED BY THE LCL CTLR.