BL65 PLT INVOLVED IN NMAC WITH A C172 AT PLR ARPT CAUSED IN PARTIAL TO A FAILED PORTABLE INTERCOM RADIO.

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I WAS ON A PLEASURE FLT WITH A GLIDER STUDENT OF MINE. WE TOOK OFF ON RWY 20 WITH CALM WINDS. RWY 20 WAS PREVIOUSLY USED. WE FLEW APPROX 45 MINS IN THE LCL AREA. RETURNING TO THE ARPT; I ELECTED TO LAND ON RWY 2 BECAUSE IT IS THE NORMAL RWY WHEN WINDS ARE CALM. I MADE SEVERAL POS ANNOUNCEMENTS DURING THE APCH. NO OTHER ACFT WERE OBSERVED OR HEARD ON MY RADIO. AS I FLARED AND TOUCHED DOWN; I SAW THE OTHER ACFT (C172) COMING TOWARDS ME. AS I WAS BRAKING; I COULD NOT DETERMINE IF THE C172 WAS LNDG OR TAKING OFF. I DECIDED TO ABORT MY LNDG. I TURNED OFF THE RWY AND TOOK OFF ON THE GRASS; TO THE R OF THE C172. WE FLEW OVER AND BESIDE THE C172; I LEFT THE PATTERN AND RETURNED FOR A NORMAL LNDG ON RWY 20. I FOUND OUT AFTERWARDS THAT MY PORTABLE RADIO'S BATTERY HAD FAILED. MY PORTABLE INTERCOM STILL FUNCTIONED; MISLEADING INTO THINKING MY RADIO WAS FUNCTIONING BECAUSE OF BACKGND. BASED ON THE KNOWLEDGE I HAD AT THE TIME; IT FELT MY EVASIVE ACTIONS WERE CORRECT. IN THE FUTURE; I NEED TO CHK MY PORTABLE RADIO TO ASSURE MYSELF IT IS FUNCTIONING. THE C172 BLENDED INTO BACKGND BECAUSE OF COLOR AND OVCST PROVIDING LITTLE CONTRAST.