SMA IN UNCTLED ARPT TFC PATTERN HAS NMAC WITH ACFT ON FINAL.

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APCHED SBM FROM W FOR PATTERN WORK. SECURED ADVISORIES FROM UNICOM AT 15 MI. ADVISED WINDS WERE FROM NE; RWY 3 IN USE. NO OTHER LCL CALLS ON CTAF 122.7; ALTHOUGH WITH FAVORABLE WX CONDITIONS; THERE WAS CONSIDERABLE RADIO TFC FROM OTHER FIELDS. ENTERED L DOWNWIND RWY 3 AT MIDFIELD. ON DOWNWIND; HEARD CALL OF ANOTHER ACFT; 5 MI AND INBOUND. PERFORMED TOUCH-AND-GO. ON DOWNWIND; I HEARD OTHER ACFT CALL SHORT FINAL. OBSERVED BEIGE PLANE ON 1/4 - 1/2 MI FINAL AND I CALLED #2 ON DOWNWIND. ANNOUNCED MY BASE AND FINAL TURNS. WHEN TURNING BASE/FINAL; I OBSERVED BLUE PLANE BELOW MY ALT ON FINAL. I RETURNED TO BASE COURSE; ANNOUNCED DIRECTION OF TRAVEL AND REQUESTED REPLY FROM OTHER PLANES IN VICINITY. THERE WAS NO ANSWER TO CALL AND I DEPARTED TO S. WISCONSIN PLTS USE UNICOM/CTAF EXTENSIVELY. I RARELY ENCOUNTER ACFT IN UNCTLED AIRSPACE WHICH HAS NOT SELF-ANNOUNCED. HOWEVER; THERE IS NO GUARANTEE THAT RADIOS WILL BE USED AND HIGH LEVEL OF VIGILANCE MUST BE MAINTAINED AT ALL TIMES. I NEVER OBSERVED BLUE ACFT ON FINAL UNTIL BASE/FINAL TURN AND MUST CONCLUDE THAT OTHER PLANE WAS NOT ILLUMINATED. DESPITE GOOD VISIBILITY; ALL ACFT SHOULD OPERATE BEACON; STROBES AND WHEN NEAR AN ARPT; A LNDG LIGHT. CONGESTED FREQ MAY HAVE BLOCKED ACFT FROM HEARING EACH OTHERS' RADIO CALLS. THE WX WAS IDEAL AND MANY PLANES WERE UP THAT DAY. THE RADIO OFTEN BROADCAST POPS AND WHISTLES AS MULTIPLE KEYS WERE DEPRESSED SIMULTANEOUSLY. ADDITIONAL UNICOM FREQS WOULD HELP; THOUGH I KNOW THERE ARE PROBS WITH THAT OPTION.