AN SMA OVER MVY; MA; HAS A NEAR MISS WITH ANOTHER SMA AS THEIR FLT PATHS COINCIDE AND THE TRACON CANNOT RECEIVE 2 SEPARATE TARGETS. EVENTUALLY THE 2 ACFT SIGHT ONE ANOTHER AND TAKE EVASIVE ACTION.

Narrative

I DEPARTED MVY RWY 24 AT ABOUT KK20 ON AUG/LL/97. WHILE CLBING TO 4500 FT; I TURNED TO A HDG OF APPROX 285 DEGS AND CONTACTED CAPE APCH ON 124.7. I WAS TOLD TO STAND BY. AFTER ABOUT 5 MINS OF WAITING; I CALLED AGAIN. THE CTLR APOLOGIZED FOR THE DELAY AND ASSIGNED ME A XPONDER CODE. SHORTLY THEREAFTER; HE SAID THAT MY XPONDER APPEARED INOP AND ASKED IF IT WAS SHOWING A REPLY LIGHT. I SAID THAT IT WAS. NEXT HE SAID HE WAS RECEIVING MY XPONDER BUT THAT IT WAS ALTERNATING BTWN THE ASSIGNED CODE AND 1200. HE THEN ASKED IF PERHAPS I SAW TFC 400 FT ABOVE ME. MY FRONT SEAT PAX AND I BOTH LOOKED AND SAW NOTHING. WE WERE NOW AT APPROX 4300 FT; CLBING AT ABOUT 105 KTS. A VERY BRIEF SECOND LATER A PIPER CHEROKEE APPEARED FROM ABOVE DSNDING THROUGH OUR ALT AND BANKING AWAY AT OUR 8 O'CLOCK POS. I BELIEVE WE MAY HAVE PASSED WITHIN 200 FT OF EACH OTHER. THE CTLR SAID THAT HE NOW SAW 2 ACFT; ME AND ANOTHER SQUAWKING 1200. AFTERWARD; IN A BRIEF CONVERSATION WITH THE CTLR; HE EXPLAINED THAT IF 2 ACFT WERE SUFFICIENTLY CLOSE THEY WOULD APPEAR AS ONE ON RADAR AND THAT THIS MIGHT EXPLAIN THE EARLIER PROB WITH MY XPONDER. I BELIEVE I MAY HAVE BEEN CLBING DIRECTLY BELOW AND SLIGHTLY AHEAD OF THE CHEROKEE; AT APPROX THE SAME SPD AND HDG; FOR MOST OF THE TIME WHILE WAITING FOR THE CTLR TO CALL ME BACK. THIS DELAY ALLOWED THESE 2 ACFT TO GET SUFFICIENTLY CLOSE THAT IT BECAME IMPOSSIBLE FOR THE CTLR TO TELL US APART. ALTHOUGH IT IS ALWAYS THE RESPONSIBILITY OF THE PLT TO MAINTAIN VISUAL SEPARATION IN VFR CONDITIONS; A MORE TIMELY IDENT WOULD HAVE PREVENTED THIS SIT FROM DEVELOPING TO THE POINT WHERE AN EVASIVE MANEUVER BECAME NECESSARY.