ATX C340 PLT TAXIED INTO POS AND HELD PER TWR CTLR INSTRUCTIONS. HOWEVER; CTLR SUBSEQUENTLY INSTRUCTED PLT TO DO A 180 DEG TURN AND GO BACK TO THE HOLD LINE.

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AS PLT OF A C340 XXXXX; I HAD RECEIVED MY CLRNC FOR AN IFR PART 135 FLT FROM APA TO SAA AND WAS TAXIING TO RWY 17L FOR DEP AS GND HAD INSTRUCTED ME. WHILE PROCEEDING TO THE RWY; I INFORMED GND THAT I WOULD HAVE MY RUN-UP COMPLETED AND WOULD BE READY FOR TKOF UPON ARRIVING AT THE RWY HOLD LINE. GND ACKNOWLEDGED MY RPT WITH; 'ROGER XXX THANK YOU.' UPON REACHING THE HOLD LINE FOR RWY 17L; I STOPPED SHORT AND; BEING #1 AT THE LINE; WAITED FOR INSTRUCTIONS TO MONITOR THE TWR FREQ AS IS CUSTOMARY AT APA. AFTER APPROX 20 SECONDS; GND ASKED ME IF I WAS READY FOR TKOF. I REPLIED; 'AFFIRMATIVE; XXX READY FOR TKOF RWY 17L.' I WAS THEN INSTRUCTED TO MONITOR TWR FREQ FOR MY TKOF CLRNC. I REPLIED 'XXX GOING TO TWR.' I SWITCHED TO TWR FREQ AND WAITED. ANOTHER 20-30 SECONDS HAD PASSED WHEN I HEARD A XMISSION FROM THE TWR; 'TWIN CESSNA XXX; TAXI INTO POS AND HOLD RWY 17L.' THERE WAS SIGNIFICANT RADIO INTERFERENCE DURING THE XMISSION; POSSIBLY CAUSED BY ANOTHER ACFT. THIS INTERFERENCE REDUCED THE CLARITY OF THE XMISSION SOMEWHAT; HOWEVER; I CLRLY HEARD THE VOICE OF A FEMALE CTLR WITH MY CALL SIGN AND THE INSTRUCTION TO TAXI ONTO THE RWY. I READ BACK; 'TWIN CESSNA XXX POS AND HOLD RWY 17L.' I RECEIVED NO FURTHER INSTRUCTIONS; CLARIFICATION OR CHALLENGE FROM THE TWR AS I TAXIED OUT TO RWY 17L. I HAD JUST BEGUN TO LINE UP ON THE CTRLINE OF RWY 17L WHEN I HEARD THE SAME CTLR WHO HAD JUST GIVEN ME CLRNC INSTRUCTIONS; 'TWIN CESSNA XXX; MAKE AN IMMEDIATE 180 DEG TURN FROM RWY 17L BACK TO THE HOLD LINE. YOU WERE NOT CLRED ONTO THE RWY. NUMEROUS ACFT INBOUND FOR LNDG. KING AIR ON 3 MI FINAL.' I TURNED BACK TOWARD THE HOLD LINE AND INFORMED THE CTLR THAT I HAD RECEIVED CLRNC TO TAXI INTO POS ON RWY 17L AND HAD READ THAT INSTRUCTION BACK TO THE TWR. THE CTLR RESPONDED THAT I HAD BEEN INSTRUCTED TO 'HOLD SHORT OF RWY 17L;' THAT IT WAS 'NO PROB' AND THAT I NEEDED TO RETURN TO THE RWY HOLD LINE. I RETURNED TO THE HOLD LINE FOR RWY 17L AND WAITED FOR TKOF CLRNC. ANOTHER 8-10 MINS PASSED; DURING WHICH TIME 3 ACFT LANDED ON RWY 17L; UNTIL I WAS INSTRUCTED; 'TWIN CESSNA XXXX; TAXI INTO POS AND HOLD RWY 17L.' I ACKNOWLEDGED THE CLRNC WITH; 'TWIN CESSNA XXX; POS AND HOLD RWY 17L' AND BEGAN TO TAXI OUT TO RWY 17L. WHILE TAXIING INTO POS ON RWY 17L; I HEARD THE SAME CTLR TALKING TO SEVERAL ACFT INBOUND INCLUDING A TFC WATCH C172 THAT WAS ON A 3 MI FINAL AND CLRED TO LAND ON RWY 17L. ONCE IN POS ON RWY 17L; I WAITED FOR TKOF CLRNC KNOWING THAT THE TFC WATCH ACFT WAS BEARING DOWN ON ME AS I SAT ON THE RWY. FINALLY I WAS INSTRUCTED; 'TWIN CESSNA XXX; FLY RWY HDG. CLRED FOR TKOF RWY 17L.' I ACKNOWLEDGED; 'RWY HDG; CLRED TKOF RWY 17L; XXX' AND BEGAN MY TKOF ROLL. FROM THAT POINT THE FLT PROCEEDED WITHOUT FURTHER INCIDENT. LOOKING AT THIS INCIDENT; I DON'T KNOW WHAT I WOULD HAVE DONE DIFFERENTLY SAVE ASKING FOR VERIFICATION OF THE CLRNC ONTO RWY 17L AFTER THAT XMISSION FROM THE TWR WAS INTERFERED WITH BY AN UNKNOWN SOURCE. AT APA THE TWR WILL SCOLD YOU IF YOU RPT YOUR POS HOLDING SHORT OF A PARTICULAR RWY. PRESUMABLY; THE PRACTICE OF NOT RPTING POS SHORT OF A RWY IS USED TO DECREASE FREQ CONGESTION IN A VERY BUSY AIRSPACE; BUT I BELIEVE THAT IT SOMETIMES CAN CAUSE CONFUSION AND ERROR ON THE PART OF CTLR AND PLT ALIKE. AFTER BEING ASKED IF I WAS READY FOR TKOF AND AFTER WAITING 20-30 SECONDS SHORT OF THE HOLD LINE WITHOUT MOVING DOES AN INSTRUCTION TO 'HOLD SHORT' MAKE SENSE? I FEEL THAT THE CTLR SIMPLY MADE A MISTAKE. I ALSO BELIEVE THAT CTLR'S COMMENT THAT IT WAS 'NO PROB' THAT WE HAD MISCOMMUNICATED REINFORCES MY POS. EVERYONE MAKES MISTAKES OCCASIONALLY; BUT IN THIS INSTANCE THE MISTAKE COULD HAVE DEFINITELY BEEN A PROB.