INST RATED PVT PLT IN A C172RG PENETRATED CLASS B AIRSPACE BEFORE OBTAINING CLRNC DUE TO BEING DISTR BY A XPONDER PROB AND CONFUSION AS TO HIS EXACT LOCATION.

Narrative

I DEPARTED PAO ARPT FOR A BAY TOUR. WHILE IN SAN CARLOS AIRSPACE; I REQUESTED CLRNC TO ENTER SFO CLASS B AIRSPACE. SAN CARLOS GAVE ME THE SQUAWK CODE FOR XPONDER. JUST AFTER THIS; SAN CARLOS TWR TOLD ME TO CHANGE FREQ TO SFO TWR 120.5. I ESTABLISHED VOICE COM WITH SFO TWR; AND THE TWR RESPONDED; 'CESSNA X; SQUAWK XXXX AND IDENT.' I RESPONDED; 'SQUAWK XXXX AND IDENT.' MY XPONDER LIGHT WAS ON BUT WHEN I PUSHED IDENT; THE LIGHT DID NOT FLASH. SFO TWR TOLD ME; 'I DO NOT HAVE YOUR XPONDER.' I TOLD THE TWR I WOULD RECYCLE THE XPONDER. I DID SO AND THE XPONDER LIGHT FLASHED. SHE AGAIN SAID SHE DID NOT HAVE MY XPONDER; AND I ATTEMPTED TO RECYCLE AGAIN. I WAS ATTEMPTING TO ORIENT MYSELF ON A SMALL BODY OF WATER OUTSIDE CLASS B AIRSPACE; BUT WHILE ATTEMPTING TO RECYCLE THE XPONDER; I MAY HAVE CONFUSED THAT BODY OF WATER WITH ANOTHER IN CLASS B AIRSPACE. SFO ASKED ME; 'I HAVE AN ACFT IN CLASS B AT 1500 FT 1 NM SW. IS THAT YOU?' I ANSWERED; 'NO; I AM AT 1100 FT W OF THE FIELD.' SFO RESPONDED; 'I SEE YOU AND YOU ARE IN CLASS B AIRSPACE.' I SAID; 'OK; MA'AM; THE XPONDER IS APPARENTLY NOT WORKING AND I AM TURNING L TO EXIT CLASS B SPACE AND RETURNING TO PALO ALTO.' THERE WAS NO AIR TFC IN MY VICINITY. SFO TOLD ME TO CALL THE TWR WHEN I GOT BACK. WHEN I RETURNED TO PALO ALTO I CALLED SFO TWR AND TALKED TO SFO SUPVR AND EXPLAINED THE SIT. I HAVE RECENTLY FINISHED MY IFR RATING AND AM FULLY AWARE OF THE REQUIREMENT FOR ENTERING CLASS B AIRSPACE. THE PROB WAS APPARENTLY CAUSED BY ME MISREADING VISUAL REF POINTS WHILE ATTEMPTING TO RECYCLE THE MALFUNCTIONING XPONDER AND BY THE ABSENCE IN THE ACFT OF DME EQUIP.