NMAC.

Narrative

PROB: I DEPARTED RWY 23; SHN; WITH MY FIRST LOAD OF THE DAY. I CALLED UNICOM; ANNOUNCED MY INTENTIONS (IE; TAKING OFF RWY 23; CLBING TO 9500 FT OVER ARPT; ETC.) TOOK OFF AND AT ABOUT 800 FT AGL I NOTICED AN ACFT CROSS MY HORIZON (FROM R TO L). I HAD THAT BAD FEELING THAT I SCREWED UP. I CALLED APCH CTL ON THE SAME RADIO I USED FOR CTAF. NO ANSWER. I AGAIN TRIED TO CALL APCH; THIS TIME ON THE OTHER RADIO (#2). IT WORKED. THROUGHOUT MY CLB I ATTEMPTED TO HAIL APCH ON #1 RADIO. NEVER GOT THEM. ONLY ON #2. SUSPECTING FAILURE OF #1 RADIO. I PROCEEDED TO USE #2 EXCLUSIVELY. IT TURNS OUT THAT I DID FORCE SOMEONE; WHO WAS ON L BASE TO RWY 05 TO CHANGE HIS PATTERN. HE ANNOUNCED HIS POS ON CTAF; SHETTON UNICOM TRIED TO CALL ME AND I DID NOT HEAR EITHER OF THEM. SHETTON UNICOM DID HEAR ME AS I WAS RE-ENTERING THE PATTERN. BUT BY THEN I WAS ON #2 RADIO. LESSON LEARNED: I SHOULD HAVE THOROUGHLY CHKED THE PATTERN BEFORE TKOF BY DOING A 360 DEG TURN BEFORE MY TKOF ROLL. I MAY HAVE SPOTTED THE TFC ON L BASE TO RWY 05 THEREBY REALIZING SOONER THAT I HAD A COMS PROB.