A HELI PLT INADVERTENTLY REDUCED RECEIVER VOLUME CTL NEARING PWK AIRSPACE.

Narrative

I WAS FLYING N ON HWY 94 (THE EDENS) ON MY WAY TO A TFC ACCIDENT IN DEERFIELD. I WAS ABOUT 1 MI S OF WHERE THE EDENS TURNS DUE W AND JOINS THE 'TRI-STATE;' WHERE THE ACCIDENT WAS. AT THIS POINT; I WAS A LITTLE OVER 5 MI E OF PWK ARPT. I CALLED PWK WITH AN INITIAL CONTACT CALL AND RECEIVED NO ANSWER. WHEN I HEARD NO RESPONSE; I FIGURED THEY MUST NOT BE OPEN YET BECAUSE IT WAS SO EARLY IN THE MORNING. I MADE A CALL IN THE BLIND SAYING; 'THIS IS CHOPPER XX; 5 MI E OF PWK; FOLLOWING HWY 94 W TO THE TRI-STATE.' LESS THAN 1 MIN LATER; COPTER YY CALLED ME ON AIR-TO-AIR AND SAID THAT PWK WAS TRYING TO GET A HOLD OF ME AND TO CHK MY RADIO. I IMMEDIATELY WENT FOR THE VOLUME KNOB AND TURNED IT UP. I CALLED PWK TWR AND THEY RESPONDED. PWK SAID THAT THE AIRFIELD WAS IFR; I WAS TO EXIT THE AIRSPACE IMMEDIATELY. I RESPONDED 'WILCO' AND WAS ALREADY ON A N HDG TAKING ME OUT. I ESTIMATE FROM THE MAP AND GPS THAT I CAME WITHIN 3 MI OF PWK. TWR THEN TOLD ME THAT I HAD CAUSED A DEV AND WAS TO CALL THE SUPVR AFTER LNDG. ON MY FLT BACK TO MDW; I DISCOVERED THAT AT THE VERY LOW SETTING WHERE THAT RADIO'S VOLUME KNOB WAS; IF IT MOVED EVEN SLIGHTLY; IT WOULD GO FROM BEING AUDIBLE TO BEING INAUDIBLE. THE XPONDER WAS RIGHT BELOW THE RADIO; AND WHEN I LEFT MDW'S AIRSPACE AND CHANGED THE CODE; MY HAND MUST HAVE BUMPED THE KNOB. THE HEADSET I WAS USING; I HAD NEVER USED BEFORE AND WAS VERY LOUD. SO I HAD THE RADIO VOLUME AT A LOW SETTING TO START WITH. CONDITIONS AT MDW WERE VFR; AND I KNEW THAT CGX WAS NOT OPEN YET; SO WHEN I RECEIVED NO RESPONSE; I THOUGHT PWK WASN'T OPEN YET. I CALLED PWK TWR ON A LANDLINE AND EXPLAINED TO THE SUPVR WHAT HAPPENED. SHE TOLD ME THAT BECAUSE THERE WAS ANOTHER NEWS HELI AHEAD OF ME; THAT I HAD CAUSED A SEPARATION PROB. I WOULD ALSO LIKE TO ADD THAT BECAUSE I WAS RECEIVING MIDWAY TWR LOUD AND CLR PRIOR TO PWK; I HAD NO REASON TO THINK THE PROB WAS WITH MY RADIO. I WOULD RECOMMEND THAT THE XPONDER AND VHF RADIO NOT BE LOCATED IN THAT CONFIGN.