A B737 PIC RPT ON A FALSE TCAS TA THAT IS ALLEGED TO BE AN ONGOING PROB WITH FALSE TARGET APPEARING 1 NM N OF THE THRESHOLD WHILE ON AN ILS APCH TO RWY 19R AT SNA; CA.

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RWY 19R ON FINAL APCH TO KSNA AT APPROX 1.5 NM FINAL ALT 3 TO 400 FT AGL. WE RECEIVED A TCAS WARNING YELLOW CIRCLE TARGET; SAME ALT NOT MOVING; ABOUT 1/2 TO 3/4 MI IN FRONT OF US. WE SAW NO TFC. THERE WAS TFC ON FINAL FOR RWY 19L AND WE HAD A HOLLOW DIAMOND DISPLAYING THAT TARGET AT OUR 11:30 O'CLOCK POSITION ON THE DISPLAY. I RPTED IT TO THE GND CTLR; WHO TOLD ME THEY CONTINUE TO SPORADICALLY GET PIREPS ABOUT THIS ISSUE. I REMEMBER THIS WAS A VERY FREQUENT PROBLEM LAST WINTER; BUT NOW IT; APPARENTLY; IS HAPPENING AGAIN. I WAS TOLD TO CALL PHONE NUMBER WHICH I DID. I SPOKE WITH A PERSON IN THE TWR; WHOSE NAME I DID NOT GET. I RPTED THE ABOVE TO THEM. I ALSO TOLD THEM THAT WHEN WE RECEIVED THE TCAS WARNING AND AFTER REALIZING THAT IT APPEARED TO BE A FALSE WARNING THAT I LOOKED OVER THE NOSE TO IDENTIFY SOMETHING ON THE GND; WHICH WOULD GENERATE THE SIGNAL. THE TARGET APPEARED TO BE ORIGINATING FROM AN AREA EITHER AROUND THE LITTLE WHITE HOUSE ON THE PARKING LOT N OF THE 405 FREEWAY. IT LOOKS LIKE THE MM HOUSE; OR THE TARGET WAS WITHIN 1 OR 2 BLOCKS N OF THE PARKING LOT RIGHT ON THE EXTENDED RWY 19R CENTERLINE. OUR ILS DME READ 2.3 NM WHEN THE TARGET APPEARED 1/2 TO 3/4 MI IN FRONT OF US. THAT WOULD EQUATE TO THE NORTHERN END OF THE PARKING LOT OR A BLOCK OR 2 N OF THAT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THIS HAS BEEN AN ONGOING SIT SINCE LAST WINTER WHEN IT WAS OCCURRING ON A FREQUENT BASIS. IT SEEMED TO TAPER OFF AT THE END OF WINTER AND APPEARED AGAIN THIS SUMMER. IT HAD BEEN SO PREVALENT THAT THE COMPANY'S FLT PLANS HAD THE WARNING ISSUED ON A DAILY BASIS. RPTR HAD SPOKEN WITH THE TWR LAST WINTER AND THEY RPTED THAT; THEY HAD IT NARROWED DOWN TO WITHIN A COUPLE OF BLOCKS FROM THE SOURCE...' RPTR FEELS THAT IT IS THE LITTLE WHITE HOUSE ON FINAL APCH AS MENTIONED IN HIS RPT. RPTR FEELS IT IS CAUSED BY SOME KIND OF AVIONICS TESTING. RPTR ALSO BELIEVES THAT THE RPTS ARE NOT RELATED TO THE FREQ OF OCCURRENCE; THAT ABOUT 1 IN 10 PLTS RPT THIS PROB. HE SAYS IT IS 'SCARY.' ONE ENDS UP FLYING BTWN 2 TARGETS; ONE ABOVE AND ONE BELOW; WITH THE TARGETS DISAPPEARING AFTER PASSING THE SITE LOCATION. RPTR IS GOING TO CONTACT HIS SAFETY CHAIR PERSON IN THE UNION TO SEE WHAT THEY ARE DOING WITH THIS SITUATION. RPTR FEELS FRUSTRATED ABOUT THIS AND WOULD LIKE TO SEE SOMETHING DONE TO RESOLVE THE ISSUE.