GRUMMAN AA5 HAS NMAC WITH SMALL TWIN WHILE ENTERING TRAFFIC PATTERN AT PDK.

Narrative

I HAD CONTACTED PDK TWR 9 NM (065 DEG RADIAL) FROM THE FIELD FOR A FULL STOP LNDG IN VFR CONDITIONS. I WAS TOLD TO RPT 4 NM OUT AND TO IDENT (1200). AT 6.4 NM (BY LATER CHKING MY GPS) I VISUALLY SAW A TWIN ENG CLBING AT MY 2 O'CLOCK POS. IF I HAD CONTINUED ON MY PRESENT COURSE (WHICH I WAS BEGINNING A GRADUAL DSCNT AT THIS POINT) I AM CERTAIN THAT WE WERE ON A DIRECT COURSE TO THE SAME POINT IN THE SKY. I IMMEDIATELY TOOK EVASIVE ACTION AND TURNED INTO A R STEEP BANK DIVE WITH THE HOPE THAT HE WOULD VISUALIZE ME AND PASS OVERHEAD; WHICH HE DID. HE CONTINUED WITHOUT ANY APPARENT CHANGE IN DIRECTION TO FLY OVERTOP AND SLIGHTLY AHEAD OF MY POS. I REALIZE HE HAD THE RIGHT OF WAY AND THAT THE TWR CTLR HAD NOT MENTIONED THAT HE HAD ME RADAR CONTACT BUT I DECIDED TO RPT IT TO HIM ANYWAY. I BELIEVE IT WAS A BARON THAT PASSED BY AND WHEN I RPTED IT TO THE TWR THE CTLR SAID THAT THE 'BARON WAS AT 3700 FT;' WHILE I WAS AT 3100 FT. I TOLD HIM THAT 'I DROPPED PRETTY FAST' TO WHICH HE ACKNOWLEDGED. I DO NOT KNOW WHO WAS TALKING TO THE BARON AT THE TIME AND I DO NOT BELIEVE THAT ANYONE IS AT FAULT. IT MAKES ME REALIZE THAT ADS-B OR SOME SIMILAR TFC AWARENESS SYS MAY SOON BECOME A NECESSITY IN AS BUSY AN AIRSPACE AS THIS.