TAXI WITHOUT CLRNC. CALL SIGN SIMILARITY AND COM CONFUSION. RPTR STATES THERE WERE 3 ACFT WITH SIMILAR CALL SIGNS AND HE MAY HAVE THOUGHT ANOTHER ACFT CLRNC WAS FOR HIM.

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TURNED UP N CARGO PAD. TUNED ATIS AND COPIED WHILE TAXIING FORWARD TO RELEASE SPOTTER. DID NOT HAVE LETTER IDENT SO AFTER SETTING ALTIMETER; ETC; LISTENED AGAIN TO GET IDENT. CALLED CLRNC AND COPIED. HAVE RWY ON SHEET ALONG WITH ATIS AND CLRNC AND THOUGHT I RECEIVED TAXI CLRNC. BACKGROUND INFO; 121.7 LISTED ON ARPT DIAGRAM AS GND FOR W SIDE 121.9 AS GND FORECAST HOWEVER; APCH PLATES NOW SHOW 121.9 AS GND. EARLY AM AND LATE PM THE CTLR TALKS OVER BOTH GND AND BOTH TWR FREQS. SO YOU CAN HEAR HIS BROADCAST ON ALL FREQS BUT ONLY ACFT ON THE ONE YOU HAVE DIALED IN. I WAS ON 121.7 AND BELIEVE I CALLED AND RECEIVED CLRNC AND TAXIED MY CALL SIGN XYZA; CALL SIGN XYZB AND XYZC; TURN UP AND TAXI AT SAME TIME; XYZC WAS ALREADY UP AND ON TXWY B; XYZB WAS TO MY L ON 121.9. AS I SAID PREVIOUSLY I THOUGHT I HAD RECEIVED TAXI PERMISSION AND READ BACK. NO COUNTER FROM GND SO I WAS TAXIING TO RWY 5L VIA TXWY B. XYZC TOOK TXWY C INTXN DEP. I CALLED GND FOR A TXWY B4 INTXN AS ACR X JET WAS HOLDING ON TXWY B WELL SHORT (SOMETIMES TKOF DELAY FOR TIME CLRNC). CALLED GND NO ANSWER. FREQ 121.7 ADJUSTED VOLUME AND CALLED AGAIN. THEY SAID WAS THAT XYZB? I SAID NO SIR; XYZA; SOME CONFUSION TO IDENT; BUT I THOUGHT DUE TO DIFFERENT FREQS I MIGHT HAVE STEPPED ON XYZB. CALLED AGAIN AND SEEMED TO BE SOME SORTING OUT OF 'WHO'S ON FIRST?' VOICE CHANGE AND CTLR SAID TXWY B4 WOULD BE A 3 MIN WAKE TURB DELAY FOR DEPARTING JET ACR X NOW MOVING; SAID I WOULD CONTINUE FOR FULL LENGTH. GOT IN VICINITY OF HOLD SHORT; SWITCHED TWR 127.45 CALLED FOR DEP RWY 5L. CTLR SAID WAS THAT XYZA? I SAID AFFIRMATIVE. CALL SIGN XYZA FOR RWY 5L. HE THEN CLRED CALL SIGN XYZA; CLRED POS AND HOLD. I'VE BEEN ROLLING THIS OVER IN MY MIND AND THEN UNUSUAL RADIO CONVERSATION SORTING OUT WHO'S ON FIRST AS I TAXIED DOWN TXWY B AND THEN THE OVERLY CAUTIOUS; TO MAKE SURE I HAD IT RIGHT; CLRNC TO POS AND HOLD AND THEN TKOF LED ME TO BELIEVE I MIGHT HAVE MESSED UP. THE SIDE TONE ON ACR X; CALL SIGN XYZA THAT DAY; BECAUSE OF BUILT IN INTERCOM SYS SOMETIMES LEADS ONE TO THINK A CALL HAS GONE OUT WHEN THE KEYING OF THE RADIO IS NOT COMPLETE. THE FULL CARGO C208'S THAT DON'T HAVE INTERCOM SYS; IF YOU DIDN'T HEAR IT NO ONE ELSE DID. ALSO THE DIFFERENT FREQS 121.9 AND 121.7 WHERE WE HEAR CTLR AND NOT OTHER ACFT. I MIGHT HAVE HEARD CALL SIGN XYZB CLRNC AND READ BACK; GETTING STEPPED ON OR NOT GOING OUT; THAT I TOOK HIS CLRNC. NOTHING WAS SAID DIFFERENTLY BY CTLRS BUT THE ONE WHO WAS ON FIRST LEFT IT TO ME THAT IF THERE WAS A SCREW UP IT WAS ME. FROM NOW ON I'LL USE 121.9 FOR EVERYTHING AND POSSIBLY IT SHOULD BE DROPPED FROM ARPT DIAGRAM AS IT IS NO LONGER ON APCH PLATES (SINCE ACR X PULLED OUT) AND USE ONLY AS ASSIGNED. I HOPE THIS IS ALL ONLY A MISCONCEPTION ON MY PART AS IT SCARES ME TO THINK I MIGHT HAVE TAXIED WITHOUT CLRNC. WE'VE HAD PROBS IN THE PAST WITH OUR CALL SIGNS; XYZA; XYZB; XYZC; AND READING BACK AND OCCASIONAL STEPPING ON ONE ANOTHER BUT NEVER ANYTHING MORE THAN THAT. BUT IT'S REALLY MADE ME DOUBT WHETHER OR NOT I WAS IN THE RIGHT WED AM.