TCASII FALSE WARNING.

Narrative

WHILE IN LEVEL CRUISE FL370 (CLRED DIRECT DAG) WE WERE ASKED BY ZLA TO TURN 15 DEGS L FOR TFC. ANOTHER ACFT WAS ASKED TO TURN 20 DEGS R FOR TFC. SINCE THERE WAS SOME URGENCY IN THE CTLR'S VOICE; WE WERE KEEPING A CLOSE EYE ON THE TCASII. I EXPANDED MY RANGE TO ABOUT THE 40 MI SCALE. WE OBSERVED 1 ACFT AT 8 O'CLOCK; ABOUT 20 MI; FL370; APPROX SAME DIRECTION. ANOTHER ACFT WAS 1 O'CLOCK; 15-20 MI; FL350; APPROX OPPOSITE DIRECTION; PASSING ON OUR R. (NEITHER OF THESE ACFT APPEARED TO BE ANY FACTOR.) SUDDENLY; A TARGET POPPED UP AT 9 O'CLOCK; 2 OR 3 MI; AT FL370. IT IMMEDIATELY TURNED YELLOW; WITH A TCASII 'TFC; TFC' TA. WE WERE UNABLE TO SPOT THE ACFT VISUALLY; AND JUST A FEW SECONDS LATER THE TARGET TURNED RED AND WE GOT A 'CLB; CLB' TCASII RA. WE INITIATED A CLB; AND WATCHED THE TARGET CROSS DIRECTLY UNDER US; AND THEN OUT THE R SIDE; UNTIL AT ABOUT OUR 4 O'CLOCK POS 1-2 MI; THE TARGET ABRUPTLY DISAPPEARED. WE NEVER GOT A CLR OF CONFLICT MESSAGE; NOR DID WE EVER SEE THE ACFT VISUALLY. I WAS LOOKING PRIMARILY OUTSIDE (PNF). THE CAPT STATED THAT THE MAX ALT HE OBSERVED DURING OUR TCASII DIRECTED RA MANEUVER WAS 37200 FT. CTR SAID THEY HAD NO ACFT IN THE AREA THAT CORRESPONDED TO OUR INTRUDER. TO THE BEST OF OUR KNOWLEDGE; THE TARGET DID NOT CLB WITH US; BUT WE ARE NOT SURE ON THAT. WE HAD SOME PROBS EARLY ON WITH FALSE TARGETS APPEARING ON TCASII. MOST OF THESE WERE DUE TO THE TCASII TRACKING YOUR OWN XPONDER. THESE WOULD USUALLY POP UP EXACTLY AT YOUR POS; AND FOLLOW YOUR TRACK AS WELL AS YOUR CLBS AND DSCNTS. I BELIEVE THE SOFTWARE HAS BEEN FIXED TO CURE THAT PROB. ONE OTHER SOURCE OF FALSE TARGETS I'VE HEARD OF ARE 'PARROTS;' OR ATC GND BASED XPONDERS USED TO CALIBRATE RADAR SCOPES. I WOULD EXPECT ONE OF THOSE TO REMAIN IN A STATIONARY GND LOCATION; AND NOT PASS UNDER US FROM L TO R.