CL65 FLC AVOIDS NMAC APCHING CVG.

Narrative

WE WERE ON APCH TO CVG; APPROX 15 MI NW OF THE ARPT. WE WERE ON A VECTOR FROM ATC AND WERE CLRED TO JOIN THE LOC FOR RWY 18R. ATC ISSUED A TA FOR US THAT WAS AT OUR 12 O'CLOCK POS APPROX 4 MI AWAY. ATC SAID THEY WERE RECEIVING NO ALT READOUT ON THE TFC AS THE TFC DID NOT HAVE THEIR XPONDER ON. THEY ISSUED AN ADDITIONAL ADVISORY WHEN THE TFC WAS AT OUR 12 - 1 O'CLOCK POS APPROX 2 MI AWAY BUT STILL NO ALT READOUT. OUR TCASII DID NOT HAVE THE TFC AS A RESULT OF HIS XPONDER NOT BEING ON. ATC WAS TALKING TO A DIFFERENT ACFT WHEN I ASKED THE CAPT IF HE EVER SAW THE TFC. HE SAID HE DID NOT SEE IT. ABOUT 5-10 SECONDS PASSED WHEN THE CAPT SHOUTED 'DIVE; DIVE!' I PUSHED THE NOSE OVER IMMEDIATELY TO APPROX 12-15 DEGS AND LOOKED TO OUR 3 O'CLOCK POS TO SEE WHAT APPEARED TO BE A C340 AT OUR ALT; TURNING INTO OUR ACFT AND WAS NO FURTHER THAN ABOUT 1/8 - 1/4 MI. WE LOST ABOUT 800 FT OF ALT IN THE DIVE AND I WATCHED THE ACFT FLY OVER OUR ACFT AT WHICH SEEMED TO BE 300 FT ABOVE US. THE PROB PRIMARILY OCCURRED BECAUSE CVG IS STILL CLASS C AIRSPACE. HAD WE BEEN CLASS B; THE ACFT WOULD HAVE BEEN REQUIRED TO HAVE HIS XPONDER ON WITH MODE C CAPABILITY. CONTRIBUTING FACTORS WERE THAT ATC SAID THE TFC WAS AT OUR 12 O'CLOCK POS WHEN IN FACT IT WAS REALLY AT OUR 3 O'CLOCK POS. ALSO; THE VISIBILITY INFLT WAS ABOUT 2 MI IN HAZE; REDUCING OUR ABILITY TO SEE THE TFC. FINALLY; THE PLT OF THE OTHER ACFT WAS TECHNICALLY DOING NOTHING WRONG AS HE WAS JUST OUTSIDE THE CLASS C AIRSPACE AND WAS NOT REQUIRED TO HAVE HIS XPONDER ON.