NON TWR ARPT UNICOM -- THE RPTR WITNESSES A PATTERN DEV AT A NON TWR ARPT.

Narrative

I WAS DOING AIR WORK N OF SOLBERG ARPT; LISTENING ON SOLBERG -- COMMON TA FREQ; CALLED ENTRY TO L DOWNWIND RWY 4 ON 45 DEG; BEHIND A CESSNA; AT TFC PATTERN ALT OF 1200 FT. ON ENTRY; I NOTICED A SECOND CESSNA APCHING THE DOWNWIND ABOVE TFC PATTERN ALT ABOUT 1 1/2 MI UPWIND OF MIDFIELD; SEEMINGLY ALMOST DIRECTLY OVER THE RWY -- I ASSUMED THE CESSNA WAS OVERFLYING SOLBERG. WHILE WATCHING IT AND CONTINUING MY DOWNWIND I NOTICED IT GRADUALLY DSNDING TO ABOUT 500 FT; PARALLELING THE DOWNWIND ABOUT 1/8 MI FROM THE RWY -- IT PASSED WELL BELOW ME AND BTWN THE CESSNA AHEAD OF ME JUST TURNING FINAL AND ME. IT CONTINUED ITS PATH AWAY FROM THE ARPT. I HAD SLOWED TO 80 KIAS ON DOWNWIND IN ANTICIPATION OF A CONFLICT -- IT CONTINUED FLYING TO ABOUT 1 MI SW OF THE ARPT AS I TURNED BASE DSNDING. MUCH TO MY SURPRISE; THE ERRANT CESSNA CALLED 'L BASE BEHIND THE PLANE AHEAD.' I LANDED AND NO CONFLICT OCCURRED. IT STRESSES THE NEED FOR CONSTANT VIGILANCE IN THE PATTERN -- NOT EVERYONE USES A RADIO OR CALLS OUT ALL LEGS OF THEIR PATTERN; AND NOT EVERYONE FLIES THE SAME TYPES OF PATTERNS.