A C150 PLT RPTS HAVING AN NMAC WITH A TWIN ENG ACFT WHILE ENTERING A TFC PATTERN. THE RPTR FEELS THAT THIS WAS CAUSED IN PART BECAUSE OF THE PROX OF SEVERAL BUSY ARPTS IN THE AREA. SEVERAL OF THESE ARPTS USE THE SAME VISUAL CHKPOINTS FOR ENTRY TO OR EXIT FROM THEIR TFC PATTERNS AND ACFT WORKING EACH ARPT USE DIFFERENT ARPT SPECIFIC FREQS WHILE OVER THESE CHKPOINTS.

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WHILE FLYING FROM F54 TO GPM I HAD A CLOSE ENCOUNTER WITH A TWIN DEPARTING GPM. I WAS JUST GETTING READY TO SWITCH FROM F54'S CTAF FREQ TO GPM TWR FREQ; WHEN I NOTICED THE TWIN TAKING ACTION TO AVOID MY ACFT. FORTUNATELY; THE TWIN SAW ME; BECAUSE I DIDN'T SEE HIM UNTIL IT WAS TOO LATE; EVEN THOUGH I WAS ACTIVELY SCANNING THE AREA FOR TFC. BECAUSE F54'S TFC PATTERN HAD BEEN SO BUSY; I WAS CONCENTRATING ON TFC AT PATTERN ALT AND FAILED TO CONSIDER POSSIBLE TFC CLBING OUT OF GPM. WHEN I LANDED; SOMEONE POINTED OUT TO ME THAT NOT ONLY DO GPM AND F54 USE JOE POOL LAKE AS A LANDMARK FOR ENTERING THEIR TFC PATTERNS; BUT NAS DALLAS AND REDBIRD ARPT ALSO USE THE SAME POINT. IT IS THEREFORE POSSIBLE TO HAVE ACFT TALKING ON 4 DIFFERENT FREQS IN CLOSE PROX TO EACH OTHER; AND IN VARIOUS STAGES OF APCH; DEP; CLB OR DSCNT. I REALLY BELIEVE THE AIRSPACE OVER JOE POOL LAKE IS VERY DANGEROUS BECAUSE OF THESE FACTORS. UNFORTUNATELY; I CAN SEE NO WAY OF CORRECTING THIS. I KNOW THE MIL AIRPLANES ARE SCHEDULED TO MOVE TO NAS CARSWELL AT THE END OF THE YR; BUT THERE WILL STILL BE MIL HELIS USING NAS DALLAS. IDEALLY; THE CITIES OF GRAND PRAIRIE AND ARLINGTON COULD BE PERSUADED TO SUPPORT 1 ARPT BTWN THE 2. HOWEVER; I DON'T THINK IT'S LIKELY. I'M NOT REALLY SURE WHAT ELSE COULD BE DONE TO CORRECT THIS PROB; BUT I DO KNOW I WILL BE EVEN MORE VIGILANT. FLT INSTRUCTORS IN THE AREA COULD BRIEF THEIR STUDENTS ABOUT THE HAZARDS SPECIFIC TO THIS AREA.