A 'HOME BUILT' PLT; TAXIING FOR TKOF AT LVK; TAXIED ONTO AN ACTIVE RWY.

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AFTER ENG START; I RECEIVED ATIS AND CONTACTED LIVERMORE GND FOR TAXI CLRNC WITH ATIS; REQUESTING R XWIND DEP. I WAS AUTH TO TAXI TO RWY 7R; AND READ BACK MY TAXI CLRNC. I WAS AWARE THAT THIS CLRNC WOULD REQUIRE ME TO CROSS RWY 7L; WHICH I WAS ALSO AWARE WAS ACTIVE. DURING TAXI; I THOUGHT IT CURIOUS THAT I WOULD BE DIRECTED TO RWY 7R; BUT FIGURED IT WAS TO ALLOW THE R XWIND DEP REQUEST. I RECALL THINKING DURING TAXI THAT MY CLRNC ALLOWS ME TO TAXI TO THE ASSIGNED RWY; XING OTHER RWYS; BUT DOES NOT ALLOW ME TO TAXI ONTO MY ASSIGNED RWY. DURING TAXI; THERE WAS CONTINUOUS RADIO TFC BTWN GND CTLR AND ACFT REQUESTING RADIO CHK. THE CTLR RPTED HIS XMISSIONS AS UNREADABLE; YET I AND ANOTHER ACFT ON FREQ COULD READ LOUD AND CLR. THE OTHER RECEIVING ACFT RPTED THIS CONDITION TO GND. UPON ARRIVING AT RWY 7L; I CHKED FOR TFC AND NOTED AN ACFT IN POS (HOLDING) ON RWY 7L. ENG WAS IDLING; AND IT WAS CLR THAT IT DID NOT POSE A HAZARD. I PROCEEDED ACROSS THE HOLD LINE (FOR RWY 7L) AND RPTED TO GND THAT I WAS PROCEEDING ACROSS RWY 7L. GND ASKED ME TO SAY AGAIN; AND I REPEATED MY XMISSION. I WAS EXITING THE R EDGE OF RWY 7L WHEN GND INFORMED ME NOT TO CROSS; THAT I HAD BEEN CLRED TO RWY 7L; NOT RWY 7R. I WAS DIRECTED TO HOLD POS BTWN RWYS; AND CONTACT TWR. AFTER RUN-UP; I WAS CLRED TO DEPART FROM RWY 7R WITH A R XWIND DEP. HUMAN PERFORMANCE CONSIDERATIONS: THERE IS NO WAY FOR ME TO BE CERTAIN AT THIS TIME IF MY CLRNC WAS TO TAXI TO RWY 7L OR RWY 7R. I CAN FURTHER NOT BE CERTAIN IF MY READBACK WAS CORRECT. I DO KNOW THAT I WAS SURPRISED BY THE CLRNC; AND WAS NOT HEARING WHAT I ASSUMED OR EXPECTED TO BE MY CLRNC. FROM THE TIME I RECEIVED TAXI INSTRUCTIONS; I WAS UNDER THE IMPRESSION THAT I WAS TO TAXI TO THE 'FAR' RWY. AS A LOW TIME PLT; AND BEING AWARE OF RWY INCURSION AS A SIGNIFICANT SAFETY CONCERN; I DECIDED TO CONFIRM WITH GND BEFORE PROCEEDING ACROSS RWY 7L. I CLRED SHOULD HAVE HELD BEHIND THE HOLD LINE UNTIL RECEIVING POSITIVE CONFIRMATION; GIVEN MY SURPRISE AT WHAT I BELIEVE WAS MY CLRNC. HAD THE ACFT IN POS ON RWY 7L NOT BEEN CLRLY HOLDING; I WOULD NOT HAVE PROCEEDED. THE APCH END OF RWY 7L IS ABOUT 300 YARDS DISPLACED FROM THE APCH END OF RWY 7R. RWY 7R IS CONSIDERABLY SHORTER THAN RWY 7L. AUDIO CLARITY OF RECEIVED XMISSIONS WAS NOT A FACTOR.