PLT OF PA28 ON TKOF ROLL AT UNCTLED ARPT NEARLY STRUCK BY AIRBORNE C172 DEPARTING FROM OPPOSITE DIRECTION ON SAME RWY.

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I LANDED AT BUY ON RWY 6; THE WINDS FAVORING THAT RWY. FOR 5 MINS PRIOR TO LNDG; I OBSERVED NO TFC TAKING OFF FROM BUY; SO I USED THE WINDS (ASOS) TO DETERMINE LNDG RWY. LANDED WITHOUT INCIDENT. SUBSEQUENT TO LNDG; I PROCEEDED TO TAXI BACK ON TXWY A TO RWY 6. THERE WAS 1 C172 IN FRONT AND 1 C172 IN THE RUN-UP AREA. UNKNOWN TO ME AT THE TIME; THERE WAS A THIRD C172 THAT HAD TAXIED TO RWY 24. #1 C172 TOOK OFF RWY 6. I TAXIED INTO POS AFTER ANNOUNCING MY INTENTIONS ON CTAF. DURING THE TKOF ROLL; I SAW #3 C172 TAKING OFF IN THE OPPOSITE DIRECTION. IT WAS AIRBORNE FAST ENOUGH TO CLR ME BY ABOUT 20 FT. WHEN I ASKED UNICOM WHO IT WAS; I WAS TOLD IT WAS #3 C172. 2 ACFT SAID THEY HEARD MY RADIO CALL; BUT NOT #3 C172. THE PLT OF #3 C172 CLAIMED TO MAKE A CALL AND NOT TO HAVE HEARD MINE. 2 FACTORS APPEARED INVOLVED: 1) POSSIBLE PLT/EQUIP FAILURE AT/ON #3 C172; AND 2) BUY'S RWY HAS A HUMP IN THE MIDDLE; PREVENTING 1 END SEEING THE OTHER. CORRECTIVE ACTIONS: LEVEL RWY AND DETERMINE RADIO FAILURE CAUSE.