C208 PLT IS SURPRISED TO FIND 2 SNOW BLOWERS ON THE RWY AT HDN FOLLOWING AN ILS APCH. ON GAR DISCOVERS HE HAD SELECTED THE WRONG CTAF FREQ. VEHICLES CLRED THE RWY TO ALLOW A SUCCESSFUL LNDG.

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AT APPROX 35 MI FROM LNDG AT HDN; I WAS ABLE TO PICK UP THE ASOS AT HDN AND NOTIFIED ZDV THAT I WOULD BE REQUESTING THE ILS RWY 10 APCH TO HDN. I BEGAN AT THIS TIME TO SET RADIOS FOR THE ILS AND REQUESTED VECTORS TO THE LOC FROM ATC. AT ABOUT 13 MI FROM HDN; I WAS CLRED FROM CTR FREQ TO ADVISORY FREQ. AT THIS TIME I SELECTED THE FREQ I HAD PREVIOUSLY STORED WHEN SETTING THE RADIOS FOR THE APCH. I MADE A POS CALL ON ADVISORY FREQ AND RECEIVED NO REPLY FROM UNICOM WHICH IS NOT TOO UNUSUAL. AT 7 MI; MADE ANOTHER POS RPT AND KEYED PLT CTL LIGHTING TO 'HIGH.' AT ABOUT 2 MI; BROKE OUT OF THE OVCST AND MADE A 'SHORT FINAL' POS RPT. IT WAS AFTER THIS I NOTICED A ROTARY SNOW BLOWER ON THE TXWY APCHING THE RWY AND IT APPEARED HE WAS GOING TO CONTINUE ONTO THE RWY OVERRUN AREA. I STOPPED MY DSCNT AND LOST SIGHT OF THE PLOW UNDER THE NOSE OF THE ACFT. AT THIS POINT; I NOTICED ANOTHER PLOW ON THE RWY ITSELF AND MADE THE DECISION THAT I WOULD BEGIN THE MISSED APCH. I BEGAN A CLB BUT DID NOT IMMEDIATELY BEGIN THE TURN TO THE VOR; SO I COULD EXAMINE THE RWY TO SEE IF THERE WAS SOME UNDISCLOSED HAZARD OR SITUATION TO BE AWARE OF DURING MY FOLLOWING APCH. NOT SEEING ANYTHING; I BEGAN MY TURN ON THE PUBLISHED MISSED APCH AND WENT TO SELECT THE CTR FREQ TO NOTIFY THEM OF THE MISSED APCH WHEN I NOTICED THAT I HAD SELECTED THE WRONG FREQ FOR CTAF 122.8 INSTEAD OF 123.0 AT HDN. I SET THE CORRECT FREQ AND CALLED HDN UNICOM TO ADVISE THEM OF THE SITUATION. THEY SAID THEY HAD 'HEARD ME ON STEAMBOAT'S FREQ' AND WERE CLRING THE RWY. WHEN THEY MADE THE CALL THAT ALL THE EQUIP WAS CLR; I WAS ON DOWNWIND AND HAD GOOD VISUAL CONTACT WITH THE RWY AND ELECTED TO LAND FROM THAT POINT. THE PRIMARY FACTOR IN THE SEQUENCE OF EVENTS WAS THE PLT'S SELECTION OF THE WRONG CTAF. BETTER AWARENESS OF THIS IS THE RESOLUTION. ADDITIONALLY ISSUANCE OF NOTAMS MAY HAVE REINFORCED THE NEED TO COMMUNICATE WITH UNICOM INSTEAD OF JUST MAKE STANDARD POS RPTS. ALSO A MEANS OF MONITORING ARTCC MIGHT GIVE ADDITIONAL ALERT OF INBOUND ACFT HELPING TO REDUCE THE CHANCE OF SIMILAR CONFLICT IN A FUTURE OCCURRENCE OF THIS TYPE.