GA-LTT UNAUTH TAXI TKOF CLOSE PROX WITH GA-SMA THAT HAD DEPARTED PREVIOUSLY.

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THIS WAS A DEMONSTRATION FLT FOR OUT COMPANY SALES DEPT. IN THE JUMPSEAT WAS THE CHIEF PLT FOR THE CUSTOMER. LOCATED IN THE CABIN WAS THE CUSTOMER. AFTER THE BRIEFING AND FIELDING SEVERAL QUESTIONS ABOUT THE ACFT; I RETURNED TO THE COCKPIT AND REVIEWED THE DEP CLRNC WITH THE COPLT. WE STARTED AND PREPARED TO TAXI. THE COPLT CALLED GND CTL AT THE SAME TIME THE PROSPECTIVE BUYER'S CHIEF PLT ATTEMPTED TO QUESTION ME ABOUT THE ACFT. MY ATTN WAS GIVEN TO THE LINE PERSONNEL'S DIRECTION OUT OF PARKING AND ONCE CLR OF OTHER ACFT; I CAME TO A FULL STOP ON THE RAMP. I ASKED THE COPLT IF WE HAD RECEIVED CLRNC TO TAXI AND HE REPLIED YES; GND SAID TAXI TO RWY 36. FROM LEAVING THE RAMP TO THE TIME WE CHANGED FROM GND CTL FREQ TO TWR CTL FREQ AT THE APCH END OF RWY 36; WE DID NOT RECEIVE ANY COM FROM GND CTL. WE CAME TO A STOP BEHIND A LIGHT HIGH WING SINGLE ENG ACFT HOLDING FOR DEP AND BEGAN OUR PRETKOF CHKLISTS. THE ACFT AHEAD OF US DEPARTED ON RWY 36. COPLT CALLED THE TWR READY TO DEPART. WE GOT NO RESPONSE FROM THE TWR AND THE COPLT ATTEMPTED TO CALL AGAIN. AT THIS TIME THE CUSTOMER GOT OUT OF HIS SEAT IN THE CABIN AND CAME FORWARD TO ASK HIS CHIEF PLT IN THE JUMPSEAT A QUESTION ABOUT THE ACFT. THE COPLT ATTEMPTED TO CALL THE TWR AND ONCE AGAIN GOT NO RESPONSE. I CALLED THE TWR READY TO DEPART. THE TWR RESPONDED AND I TURNED AROUND TO ASK THE PAX TO TAKE HIS SEAT. ONCE LINED UP ON THE RWY; CHKLISTS COMPLETE; I ASKED THE COPLT; 'ARE WE CLRED TO GO?' HE REPLIED; 'YES.' TWR SAID; 'CLRED FOR TKOF; CONTACT OAKLAND CENTER LEAVING 10000'.' I SAW THE LIGHT SINGLE ENG ACFT THAT HAD DEPARTED BEFORE US APPROX 2-2 1/2 MI OFF THE DEP END OF THE RWY ON THE CENTERLINE. WHEN I SAW THE OTHER ACFT I WAS STILL OVER THE RWY AIRBORNE SO I IMMEDIATELY MOVED TO THE RIGHT OF CENTERLINE TO KEEP IT IN SIGHT DURING CLBOUT. NEVER LOSING SIGHT OF THE TFC; I CLBED TO AN ALT OF APPROX 1000' ABOVE IT; THEN INITIATED A TURN TO JOIN THE STANDARD INSTRUMENT DEP. WE DID NOT RECEIVE ANY COM FROM THE TWR FROM THETIME WE STARTED OUR TKOF ROLL BEFORE REACHING 10000'; SO THE COPLT ATTEMPTED TO CALL ZOA AS INSTRUCTED. AFTER 2 UNSUCCESSFUL ATTEMPTS BY THE COPLT TO CALL CENTER; I PICKED UP MY MIC; CALLED ZOA AND GOT AN IMMEDIATE RESPONSE. AT THIS TIME WE REALIZED THAT THE COPLT WAS HAVING DIFFICULTY XMITTING. WE TRADED MICS AND THAT DID NOT CLR UP THE PROB. THE COPLT THEN WIGGLED HIS MIC PLUG AND CALLED CENTER AGAIN. THIS TIME THEY SAID THEY HEARD HIM LOUD AND CLEAR. TO OUR KNOWLEDGE; AT NO TIME DID WAS HAVE A PROB RECEIVING. ON EACH FREQ AT THE TIME IT WAS SELECTED (GND CTL; TWR AND CENTER) WE WERE ABLE TO HEAR CTLRS AND OTHER ACFT. THE FOLLOWING MORNING I SPOKE WITH SOUTH LAKE TWR CHIEF. HE INFORMED ME THAT THEY BELIEVE WE HAD TAXIED AND TAKEN OFF W/O CLRNC. I ASKED HIM IF AT ANY TIME WHILE WE WERE OPERATING ON OR AROUND TVL; DID THE TWR RECEIVE OR RECORD ANY XMISSIONS OF CARRIER SIGNALS WITH NO VOICE. HE REPLIED NEGATIVE. I ASKED HIM IF WE WERE TAXIING W/O CLRNC TO DO SO; WHY DID NOT GND CTL QUESTION OUR ACTIVITY. HE HAD NO RESPONSE. I ASKED HIM WHY; IF WHEN WE CONTACTED THE TWR HOLDING SHORT OF THE RWY; THE TWR DID NOT QUESTION WHAT WE WERE DOING THERE W/O CLRNC FROM GND CTL. HE REPLIED THAT HE DID KNOW; HOWEVER; OUR CLRNC AT THE RWY WAS INTO POS AND HOLD; NOT A CLRNC TO DEPART. I ASKED HIM WHY; IF THE TWR SAW OUR ACFT BEGIN A TKOF ROLL W/O CLRNC TO DEPART; AND THE TWR SAW A POSSIBLE CONFLICT WITH THE PREVIOUSLY DEPARTED ACFT; DID NOT THE TWR TELL US TO STOP. HE TOLD ME HE WOULD NOT DISCUSS IT AT THAT TIME. I ASKED HIM WHY WE DID NOT HEAR FROM THE TWR BEFORE WE CONTACTED ZOA. HE SAID THAT OUR IFR CLRNC WAS TO CONTACT CENTER OUT OF 10000'. I BELIEVE THE PROB AROSE FROM A PROB WITH THE COPLT'S XMITTER. I BELIEVE THE PROB WAS COMPOUNDED BY: MY CONFIRMING THE CLRNC TO TAXI AND TKOF WITH THE COPLT W/O REQUESTING THAT HE CALL THE CTLR IF I HAD A DOUBT; AMBIENT NOISE LEVELS INSIDE THE ACFT; INAPPROPRIATE PAX ACTIVITY INSIDE THE ACFT; LACK OF COMMENT BY GND CTL THAT WE MAY HAVE COPIEDANOTHER ACFT'S CLRNC TO TAXI--WE WOULD HAVE MOST LIKELY FOUND THE RADIO PROB AT THAT TIME; AND INACTION BY THE TWR CTLR WHEN WE INITIATED OUR TKOF ROLL AND HE SAW WHAT COULD BE A POSSIBLE TFC CONFLICT. I BELIEVE THIS SITUATION COULD HAVE BEEN AVOIDED BY MORE COMPLETE AND BETTER COM BTWN THE CTLRS AND THE ACFT.