CPR HELI HAS A POTENTIAL CONFLICT WITH A TV TFC WATCH ROTARY NEAR A COMMONLY USED VFR HELI CHK POINT. PLT WAS SLOW ON OBTAINING THE SELF ANNOUNCE FREQ USED BY ARR ROTARY WINGED TFC IN ORD AREA. IN ADDITION; HIS TFC COLLISION AVOIDANCE DEVICE AURAL WAS MUTED.

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I TOOK OFF FROM OUR COMPANY HELIPAD AT ABOUT AB20 AM. OUR FACILITY IS ABOUT XX OF ABC AIRFIELD. MEIGGS TWR HAD REQUESTED THAT I RPT CLR OF THE AREA TO THE NW. UPON REACHING THE NW BOUNDARY I RPTED CLR. HOWEVER; TWR WAS SLOW TO RESPOND. AFTER 3 CALLS THEY SAID FREQ CHANGE APPROVED. AS A RESULT OF THIS DELAY I WAS NOW ALMOST HALFWAY TO OHARE (ORD) AIRFIELD. I IMMEDIATELY CHANGED OVER TO ORD TWR AND REQUESTED AN ELMWOOD ONE ARR FOR LNDG ORD HELISTOP. THEY CLRED ME IN AND MADE NO MENTION OF ANY POSSIBLE TFC CONFLICTS. I SET MY TCAD; TFC COLLISION AVOIDANCE DEVICE; TO 1400 FT ALT AND PROCEEDED INBOUND. I WAS NOW ABOUT 8 NM SE OF ORD AND ABOUT TO PASS OVER THE GRAIN ELEVATOR; A HEAVILY USED IDENT POINT FOR HELIS IN THE AREA. I WAS ABOUT TO SET MY SECOND RADIO TO FREQ 123.05 TO MONITOR THE HELI COMS WHEN OUT OF THE CORNER OF MY R EYE I SAW TV TFC WATCH HELI CONVERGING AT WHAT LOOKED LIKE MY ALT. I PULLED UP ON THE CYCLIC AND CLBED 200 FT AND PASSED BEHIND AND HIGH. HE THEN CALLED ON 123.05 AND ASKED IF I WAS TALKING TO OHARE; WHICH I RESPONDED; NO; I WAS LISTENING AT THAT TIME. HE THEN SAID I WAS BEHIND HIS L WINDOW POST. AND HE WAS BEHIND MY R WINDOW POST. I BELIEVE HE MAY HAVE MADE HIS POS CALL WHEN I WAS TALKING TO EITHER MEIGGS OR OHARE. AS A RESULT I DID NOT HEAR HIS POS CALL AS I WAS BUSY ON THE OTHER FREQ; MAKING RADAR CONTACT AND GETTING CLRNC INTO OHARE'S AIRSPACE. EVEN THOUGH I HAD A TFC COLLISION AVOIDANCE DEVICE ON BOARD; ITS ALARM DID NOT SOUND BECAUSE I HAD ACCIDENTALLY HIT THE MUTE BUTTON ON SETTING THE ALT ALERT. AS A RESULT I WAS NOT AWARE OF THE POSSIBLE COLLISION POTENTIAL. THIS IS A CLASSIC CASE OF WHAT CAN GO WRONG WILL; AND I CAN ONLY SAY THAT ONE CAN NEVER LOOK AROUND ENOUGH TO HELP PREVENT A MIDAIR COLLISION.