A C172 PLT; WHILE ENTERING DOWNWIND AT A NON TWR ARPT; ENCOUNTERED ANOTHER ACFT ENTERING DOWNWIND AT THE SAME TIME AND PLACE.

Narrative

I WAS FINISHING THE LAST LEG OF MY FIRST SOLO XCOUNTRY FLT TO POTOMAC AIRFIELD KVKX. STANDARD NBOUND INBOUND PROC CALLS FOR MAKING A RPT OVER A MARINA NEAR FORT WASHINGTON PARK; MD. AT 1000 FT; I MADE MY CALL ON 122.80; THE CTAF FOR KVKX. IN THE 3 MINS IT TOOK TO GET TO THE AIRFIELD FROM THERE; I HEARD NO ONE ELSE RPT A POS. I DID; HOWEVER; HEAR SOMEONE KEY THEIR MIKE 3 TIMES TO GET A UNICOM WIND RPT FROM KVKX; BUT IT WAS NOT CLR WHETHER THEY WERE IN THE AIR OR ON THE GND. JUST AS I WAS ABOUT TO ENTER THE 45 DEG FOR DOWNWIND TO RWY 24 VKX; I WAS ABOUT TO KEY MY MIKE TO MAKE ANOTHER RPT WHEN SOMEONE ELSE MADE THE EXACT SAME RPT I WAS ABOUT TO MAKE. I SCANNED THE AREA QUICKLY AND FOUND A LOW WING ACFT ENTERING THE DOWNWIND FOR RWY 24 EXACTLY IN FRONT OF ME. HAD I NOT SEEN THE ACFT; OUR PATHS WOULD HAVE CONVERGED ON THE DOWNWIND. I IMMEDIATELY PERFORMED A L 360 DEG TURN OVER THE FIELD AND RPTED MY INTENTIONS AND MANEUVER TO RE-ENTER THE TFC PATTERN ON DOWNWIND. UPON RETURNING TO DOWNWIND; I SAW THE OTHER ACFT ON BASE; SO I PROCEEDED WON WITHOUT FURTHER INCIDENT. UPON TALKING WITH THE OTHER PLT; I FOUND HE WAS ENTERING VKX FROM THE N; AND HAD JUST SWITCHED FROM ANDREW'S RADAR FREQ. SINCE WE WERE BOTH ON DIFFERENT FREQS; WE HAD NO WAY OF KNOWING THE OTHER WAS THERE. KVKX LIES 1/2 MI S OF ANDREWS AFB (ADW) CLASS B AIRSPACE 'SFC' ZONE; THUS THE OTHER PLT WAS TALKING TO ADW WHEN I MADE MY POS RPT.