NMAC; 2 LIGHT CIVIL ACFT.

Narrative

FIRST NOTIFICATION BY ATC WAS 'TFC 12-1 O'CLOCK; 5 MI; OPPOSITE DIRECTION; 13800 FT; CLBING.' (I WAS AT 14000 FT.) WARNING ACKNOWLEDGED AND SCAN BY PLT AND PAX BEGAN AND PULSE LIGHT TURNED ON. APPROX 15 SECONDS LATER; THE OPPOSING TFC WAS SPOTTED JUST R OF THE NOSE; SLIGHTLY BELOW; AND ON A POTENTIAL COLLISION COURSE. AS ATC CALLED 'TFC COLLISION ALERT; 1 MI; SUGGEST YOU CLB;' A RAPID CLBING L TURN WAS ALREADY INITIATED. A WHITE WITH GREEN LIGHT TWIN PASSED ABOUT 200 FT BELOW AND 100 FT TO OUR R (WE CLBED 200-400 FT). THE CTLR RPTED THAT THE TARGET HAD JUST APPEARED ON RADAR JUST BEFORE THE ADVISORY. SINCE THE TWIN HAD ALT ENCODING; WE SHOULD HAVE PROVIDED PRIMARY AND SECONDARY TARGETS ON RADAR UNLESS SUPPRESSED AS A VFR TARGET. ALTHOUGH 'SEE AND AVOID' WAS APPROPRIATE ON THIS DAY WITH EXCELLENT VISIBILITY; IT'S DIFFICULT TO FIND TARGETS CLOSING AT 350 KTS; EVEN WITH ADVISORIES. PERHAPS THE RADAR SOFTWARE COULD 'UNSUPPRESS' TARGETS WITHIN 10-20 MI; ESPECIALLY WHEN A TFC CONFLICT IS ANTICIPATED. LET'S USE THE COMPUTER SOFTWARE TO PROTECT PLTS; NOT JUST SWITCH ON CTLRS.