C172 PLT ON THE WRONG RADIO FREQ HAS AN NMAC WITH ACFT IN THE TFC PATTERN AT A NON-TWRED ARPT.

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ARRIVING AT DEST ARPT; I BEGAN STANDARD COM PROCS RPTING 5 MI OUT FOR LNDG; ENTERING 45 DEG L DOWNWIND. JUST AS I REDUCED PWR AT END OF RWY FOR DSCNT; MY PAX POINTED OUT TFC XING ABOUT 300 FT AHEAD; SAME ALT. I INCREASED PWR AND TURNED R 90 DEGS KEEPING TFC IN SIGHT. THE OTHER PLANE TURNED 180 DEGS TO THE L REVERSING THEIR COURSE. AS WE WERE THEN GOING IN OPPOSITE DIRECTIONS AND I NOTICED ANOTHER PLANE AHEAD ABOUT 1 MI AWAY I SOON LOST SIGHT OF THE ORIGINAL TFC. I WONDERED WHY I DID NOT HEAR RADIO TFC AND CHKED THAT MY RADIO WAS ON BY TESTING SQUELCH. FOLLOWING THE SECOND PLANE I THEN FLEW AT 1000 FT AGL. APPROX 2 MI OUT FROM ARPT PARALLEL TO RWY AND AGAIN ENTERED A L DOWNWIND STAYING APPROX 1 MI BEHIND SECOND AIRPLANE AND XMITTING ENTRY TO L DOWNWIND; TURNING BASE AND TURNING FINAL. AT APPROX 150 FT ABOVE GND ON FINAL I SAW THE SAME PLANE (#1 ABOVE) TURNING ONTO FINAL APPROX 50 FT BELOW ME AND 100 FT AHEAD. I ADDED FULL PWR AND ABORTED MY LNDG; TURNING L AND CLBING TO PREVENT PLANE FROM CLBING INTO ME FROM BELOW. I THEN WENT TO COTTAGE GROVE ARPT. ON THE WAY THERE; I DOUBLE CHKED CHART FOR UNICOM FREQ AND CHKED RADIO AND MY PAX POINTED OUT RADIO WAS SET FOR 128.80 NOT 122.80. I TUNED THE RADIO TO 122.80 AND IMMEDIATELY NOTED NORMAL RADIO TFC FROM NUMEROUS ARPTS IN THE AREA. I LANDED UNEVENTFULLY AT COTTAGE GROVE ARPT. THE PROB ON MY PART WAS INCORRECTLY ENTERING RADIO FREQ WHICH PREVENTED ME FROM BEING AWARE OF PLANE MAKING NON STANDARD APCHS. THE PROB ON THE OTHER PLT'S PART WAS RELYING TOTALLY ON RADIO COM TO BE AWARE OF TFC IN THE AREA AND NOT USING STANDARD TFC PATTERN TO ALLOW OTHER TFC TO BE AWARE OF HIM OR HER. CORRECTIVE ACTION WOULD BE TO SCAN NON STANDARD TFC PATTERN AREAS; FLY STANDARD PATTERN WHENEVER POSSIBLE; AND ALWAYS ASSUME ANOTHER PLANE IS IN THE PATTERN AT AN ARPT JUST TO KEEP THE MINDSET TO LOOK FOR OTHER TFC.