POTENTIAL CONFLICT WITH UNKNOWN VFR TFC IN AREA.

Narrative

ENRTE FROM PHOENIX; AZ; TO PALM SPRINGS; CA; APPROX 10-15 NM FROM THE ARPT; WE WERE CLRED FOR A VISUAL APCH TO RWY 30 AT PALM SPRINGS REGIONAL ARPT. SHORTLY AFTER; WHILE DSNDING THROUGH 6500 MSL; WE SAW THE SINGLE ENG HIGH WING SMA MOVE FROM OUR 9 O'CLOCK TO 8 O'CLOCK POS AND PASS APPROX 200 FT BELOW AND BEHIND OUR ACFT (LATERAL DISTANCE APPROX 1/8 MI). THERE WERE SCATTERED CLOUDS FROM OUR 10 O'CLOCK TO 7 O'CLOCK POS AT 3000-6000 MSL. THE ARPT WAS AT OUR 12-1 O'CLOCK POS AND WE WERE 3/4 MI LATERAL DISTANCE FROM THE CLOUDS. NO TFC WARNING WAS GIVEN BY APCH CTL. WHEN QUERIED; WE WERE SWITCHED TO TWR. AFTER A TELEPHONE CALL AND LENGTHY DISCUSSION WITH APCH CTL (WHO HAD REVIEWED THEIR TAPES) IT WAS DETERMINED THAT NO RADAR IDENT HAD BEEN MADE ON THE OTHER ACFT. IT WAS OUR CONCLUSION THAT THE SMA DEPARTED A NEARBY UNCTLED ARPT (BERMUDA DUNES OR THERMAL) VFR AND DID NOT MAINTAIN REQUIRED CLOUD SEPARATION. THIS FACT ALONG WITH THE ARCHAIC AND INADEQUATE RADAR CAPABILITIES OF PSP APCH LIKELY CAUSED THIS NEAR MISS THAT SEVERAL OF OUR PAX WERE CONCERNED ABOUT. DUE TO THE POS AND SPD OF OUR ACFT AND THE 'LAST SECOND' VISUAL IDENT WITH THE OTHER ACFT; NO EVASIVE MANEUVERING WAS MADE.