PA32 PLT AND PLT PAX; AND A HELI HAD AN NMAC AT FDK.

Narrative

I WAS PERFORMING TOUCH-AND-GO PATTERN WORK ON RWY 30 AT FDK. I DEPARTED FDK. MY INTENTIONS WERE ANNOUNCED ON UNICOM AT ALL POINTS FROM TKOF AND THEN IN THE PATTERN. NO TFC WAS OBSERVED. AFTER ANNOUNCING BASE LEG; A HELI ANNOUNCED THAT IT TOO WAS ON BASE. THE HELI COULD NOT BE OBSERVED. A REQUEST WAS MADE OVER UNICOM: 'HELI; DO YOU SEE CHEROKEE ALSO ON BASE?' NO RESPONSE. I TURNED FINAL AND AGAIN ANNOUNCED OUR POS OVER UNICOM. AFTER TURNING FINAL; HELI WAS SPOTTED ON L SIDE OF ACFT ON A PARALLEL COURSE AT A LOWER ALT. UPON OBSERVING HELI; WE SURRENDERED THE RIGHT-OF-WAY; ANNOUNCED THAT WE WERE BREAKING R AND PROCEEDED TO MAKE A SHARP R TURN UNTIL WE WERE CLR OF THE FINAL FLT PATH AND THEN TURNED UPWIND AND AGAIN ANNOUNCED OUR POS ON UPWIND. NO FURTHER RADIO BROADCASTS WERE HEARD FROM THE HELI. MY ACFT AND HELI WERE NEVER ON CONVERGING COURSES. SUPPLEMENTAL INFO FROM ACN 596835: I WAS IN THE R SEAT ANNOUNCING ON THE RADIO WHILE THE PLT PERFORMED TOUCH-AND-GO PATTERN WORK ON RWY 30 AT FDK.