C172 PLT RECEIVING TA'S FROM NORCAL APCH CTLR ENTERED SNS CLASS D WITHOUT COORD AND HAS A NEAR MISS WITH A PA28 IN THE SNS TFC PATTERN.

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IT IS A COMMON MYTH IN SOUTHERN CALIFORNIA THAT IF YOU ARE ON VFR FLT FOLLOWING WITH SOCAL TRACON THAT YOU ARE 'AUTOMATICALLY' CLRED THROUGH ALL CLASS C AND CLASS D IN THE LOS ANGELES BASIN. THE FACT IS THAT SOCAL DOES SUCH A GREAT JOB COORDINATING HDOFS TO THE LCL TWR CTLRS THAT THOSE OF US WHO LEARNED TO FLY IN SOUTHERN CALIFORNIA TAKE IT FOR GRANTED AND ASSUME THAT THIS IS TRUE EVERYWHERE. MOREOVER; WE BEGIN TO THINK THAT THE FINAL HDOF FROM TRACON TO TWR IS SOLELY ATC'S RESPONSIBILITY. I FELL INTO THAT TRAP! I WAS ON A VFR FLT WITH FLT FOLLOWING FROM SNA TO SNS. CTLR HDOFS WENT SMOOTHLY FROM SNA TWR TO SOCAL TRACON TO ZLA TO ZOA TO NORCAL TRACON. HOWEVER; I REALIZED THAT I WAS IN SALINAS CLASS D AIRSPACE BUT THAT I WAS STILL NOT HANDED OFF TO THE SNS TWR CTLR. THIS WAS MY FIRST TRIP TO THE SALINAS AREA AND I WAS UNFAMILIAR WITH THE AREA AND LCL PROCS. I WAS NOT RECEIVING DME FROM SNS VORTAC. VISUALLY; THE ARPT LOOKED TOO CLOSE. I QUERIED NORCAL TRACON AND WAS TOLD TO SWITCH FREQ TO TWR. WHEN I DID; A PIPER CHEROKEE WHO SEEMED TO BE FLYING A WIDE PATTERN FOR RWY 26 PASSED VERY CLOSE TO ME. I TURNED AND THE CHEROKEE TURNED TO AVOID A COLLISION. THE CTLR IN THE TWR ASKED ME TO CALL HIM UPON LNDG. I APOLOGIZED TO THE CTLR AND EXPLAINED TO HIM MY MISUNDERSTANDING REGARDING THE LATE HDOF FROM NORCAL TRACON. I AM GRATEFUL THAT THIS DID NOT END FAR WORSE AND I WILL NEVER REPEAT THIS MISTAKE! AS PIC; ALL AIRSPACE IS MY RESPONSIBILITY AND I WILL NEVER MAKE THE SAME ASSUMPTIONS REGARDING THE FINAL HDOF; ALLOWING A LATE HDOF TO OCCUR.