PA28 PLT MAKES APCH TO UNCTLED FIELD UTILIZING WRONG UNICOM FREQ. PLT ON RWY ABORTS TKOF AFTER NOTICING TFC OPPOSITE DIRECTION ON FINAL.

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I WAS APCHING LAM FOR FINAL ON RWY 27. I HAD ALREADY RECEIVED THE AWOS AT LAM AND HAD CHANGED FREQS TO WHAT I THOUGHT WAS 123.0. AS I APCHED THE FIELD AND AT THE DISTANCES RPTED ABOVE; I NOTICED AN AIRPLANE ABORTING A TKOF ABOUT 1000 FT FROM THE END OF THE RWY. I IMMEDIATELY SET UP THE AIRPLANE TO GO AROUND. I SCANNED MY RADIO AND NOTICED THAT IT WAS ON '123.SOMETHING' BUT NOT 123.0. I IMMEDIATELY CHANGED THE CORRECT FREQ AND CALLED AGAIN IN THE BLIND THAT I WAS GOING AROUND. THE ABORTED PLANE ANSWERED AND I APOLOGIZED FOR MY ERROR. I WENT AROUND WHILE THE OTHER PLANE TAXIED BACK TO THE RUN-UP AREA. I TOLD HIM THAT I WOULD HOLD OUTSIDE THE AREA AND WAIT FOR HIS TKOF BUT HE SAID THAT HE NEEDED TO CHK HIS AIRPLANE AS HE HAD TO MAKE AN ABRUPT STOP. I LANDED AND HE WAS INSPECTING HIS AIRPLANE. AS I SHUT DOWN HE WAS STARTING HIS ENG. AS FAR AS I CAN TELL; THERE IS NO DAMAGE TO EITHER ACFT. THE OTHER PLT DID HAVE TO HIT HIS BRAKES HARD TO STOP BEFORE THE END OF THE RWY. MY ERROR WAS NOT CHKING THE RADIO FOR THE PROPER UNICOM FREQ 123.0. ADDITIONALLY; I WAS FOCUSED ON THE END OF THE RWY AND DID NOT SCAN THE LENGTH OF THE RWY AS I TURNED FINAL APCH. LAM IS 1-WAY IN (RWY 27) AND 1-WAY OUT (RWY 9).