PLT OF A C182 CLBED INTO CLASS B AIRSPACE WHEN DEPARTING AN ARPT UNDERLYING CLASS B AIRSPACE.

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TKOF PDK NEAR SUNSET FOR VFR TO AIK. PDK CTAF (CTL TWR) WAS CTLING. PRIOR TO REQUESTED L TURN TO ON-COURSE (105 DEGS) WHICH PDK HAD APPROVED; BUT I HAD NOT EXECUTED; PDK TWR INSTRUCTED ME TO CHANGE TO ATL APCH. I CONTINUED TO CLB ON RWY HDG (TKOF) OF 200 DEGS (I WAS AWARE THAT THE FLOOR OF THE CLASS B AIRSPACE WAS 8000 FT AT PDK AND EXTENDED S FOR; I THOUGHT; 6-8 MI AND MY INTENTION WAS TO TAKE OFF AND IMMEDIATELY TURN E (105 DEGS) AND WOULD NOT HAVE TO WORRY ABOUT WHERE THE CLASS B AIRSPACE FLOOR DROPPED TO 6000 FT) WHILE ATTEMPTING TO CALL ATL APCH. WHEN THEY FINALLY ANSWERED (4TH OR 5TH XMISSION) THEIR ONLY INSTRUCTION WAS 'REMAIN VFR' WITH NO ALT RESTR. I REPLIED THAT 'WILL REMAIN VFR. I AM IN YOUR AIRSPACE (MEANING BELOW CLASS B; BUT CTLED BY ATL APCH); WILL FOLLOW YOUR INSTRUCTIONS.' IMMEDIATELY TURNED L TO 105 DEGS AND CONTINUED TO CLB. AT 7500 FT; I RECEIVED A CALL ASKING IF I HAD JUST DEPARTED PDK. I ANSWERED 'YES.' CTLR THEN ASKED IF I WAS FAMILIAR WITH ATL CLASS B AIRSPACE. I REPLIED THAT I WAS AND BELIEVED I WAS IN THE 8000 FT FLOOR RING. HE THEN INSTRUCTED ME TO INITIATE IMMEDIATE DSCNT TO 5500 FT; WHICH I DID. HE GAVE ME A TELEPHONE NUMBER AND INSTRUCTED ME TO CALL THE TWR WHEN I LANDED. I CALLED THE TWR WHEN I LANDED AND DISCUSSED SIT WITH SUPVR. BETTER DEP PLANNING BY ME AND ATL APCH ANSWERING VFR CALLS PROMPTLY; GIVING ALT RESTRS IN REMAIN VFR INSTRUCTION WOULD HAVE HELPED AVOID THIS SIT.