LGT X TAKES EVASIVE ACTION OF LEVELOFF WHEN TCASII INDICATES TFC. LGT Z AHEAD; EXPERIENCES NMAC WITH SAME TWIN; ACFT Y. SIMULTANEOUS LOSS OF ACFT RETURN ON ARTCC RADAR ACFT TCASII.

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WE WERE MAKING A DSCNT INTO FLL AND HAD BEEN CLRED BY ZMA TO DEPART FOR 9000 FT WHEN AT ABOUT 10800 FT I HEARD A FAINT AURAL FROM THE TCASII CALLING OUT TFC. I LOOKED AT MY VVI AND SAW A TARGET AT 12 O'CLOCK AT ABOUT 700 FT. I ALERTED THE CAPT WHO WAS FLYING THE ACFT AND HE STARTED TO LEVEL OFF. I NEXT SAW THE TARGET AT MINUS 300 FT AND THEN AT OUR ALT AT ABOUT 11 O'CLOCK. WE WERE VMC WITH BUILDUPS AROUND US AT 6-10 MI. AT ABOUT THAT TIME WE GOT AN RA AND AS I LOOKED UP TO SAY SOMETHING TO THE CAPT; I SAW THE TARGET CLB UP THROUGH OUR ALT AT ABOUT 11 O'CLOCK AND PASS BEHIND US. I RPTED THE TFC TO THE CAPT WHO THEN IDENTED IT AS A TWIN TURBOPROP. WE CONTINUED OUR DSCNT TO 9000 FT. I ASKED THE CTR IF THEY HAD ANY KNOWLEDGE OF THE TFC THAT HAD JUST PASSED BY US AT LESS THAN A MI AND THEY DIDN'T SEEM TO HAVE ANY KNOWLEDGE OF IT. THEY ASKED US WHAT KIND IT WAS AND WE RPTED IT AS A TWIN TURBOPROP. BEFORE WE LEFT THE FREQ; I HEARD ANOTHER ACFT ASK ABOUT WHAT APPEARED TO BE THE SAME ACFT. SUPPLEMENTAL INFO FROM ACN 273795: WHILE CONDUCTING RADAR TRAINING WITH EXTENSIVE WX DEVS AND COMPLEX RADAR SITS AT ZMA; SECTOR R24; I EXPERIENCED A NEAR MIDAIR WITH ACR Z. THE ACFT RPTED TFC AT HIS ALT (APPROX 12700 FT) AT WHICH TIME I DISPLAYED AND ISSUED TFC '12 O'CLOCK 1 MI INDICATING 10400 FT.' THIS TARGET WAS DISPLAYED AS A 'V104' WHICH WAS VERY CONFUSING TO MYSELF. TFC AT THIS ALT SHOULD BE DISPLAYED AS 'I104.' THIS IS CALLED A MODE C INTRUDER. I WAS THEN INFORMED BY THIS ACR Z THAT 'NO; THE TFC IS AT OUR ALT' (APPROX 12300 FT). I CLRED ACR Z TO TAKE ANY MANEUVERS NECESSARY TO MISS THE TFC. APPROX 10 MI IN TRAIL WAS ANOTHER ACR X ACFT. I ASKED THE FIRST ACR Z WHAT TYPE ACFT THE TARGET WAS AND HE SAID 'KING AIR TYPE.' I THEN ISSUED THE TFC TO THE SECOND ACFT X AT 12 O'CLOCK; 8 MI INDICATING 12700 FT (K127). HE RPTED LOOKING FOR TFC AT WHICH TIME I COMPLETELY LOST THE TARGET; CODE AND ALT OF THE VFR TFC AND I INFORMED THE ACFT THAT I WAS NO LONGER DISPLAYING THE TFC. SHORTLY AFTER THIS THE SECOND ACR X RPTED VISUAL AT '113 OR 114' AND NOT A FACTOR. I WAS AMAZED THAT I DID NOT EVEN DISPLAY A TARGET. THE FIRST ACR Z LANDED AT FLL AND FILED A NMAC RPT. MY RADAR DID NOT ADEQUATE DISPLAY THE MODE C OF THE TFC. I'M CURIOUS TO KNOW WHAT ACR Z TCASII DISPLAYED CONCERNING THE TFC'S ALT.