A C172 PLT; ON APCH TO KRUE; A NON TWRED ARPT; HAD AN NMAC WITH ANOTHER ACFT.

Narrative

I WAS FLYING A MULTIPLE LEG TRAINING MISSION. DURING THE LEG FROM ARPT X TO ARPT Y; I WAS FLYING AT 2500 FT MSL TO PRACTICE THE NDB APCH AT ARPT Y. ABOUT 6-8 NM SE OF ARPT Y; WE OBSERVED ANOTHER ACFT (HIGH WING; SEL) TURNING AWAY FROM US. I WOULD ESTIMATE THE DISTANCE AS 200-300 FT BELOW US AND 300-400 FT TO THE SIDE. PRIOR TO THE OTHER ACFT TURNING; NEITHER OF US SAW THE OTHER ACFT. WE CONTINUED TO ARPT Y AND ACCOMPLISHED AN NDB HOLDING PATTERN AND APCH FOR TRAINING AND CURRENCY. THE WX WAS VFR AT THE TIME. AFTER LNDG AT ARPT Y; I DISCOVERED THAT I HAD NOT CHANGED THE RADIO TO ARPT Y UNICOM. AS A RESULT; I DID NOT HEAR ANY TFC CALLS FROM ARPT Y NOR DID ANY TFC HEAR ME GIVE THE CTAF CALL INBOUND TO ARPT Y. OBVIOUSLY; I ERRED BY NOT HAVING THE CORRECT FREQ IN THE RADIO. WHILE ON THE GND AT ARPT Y; AFTER I HAD DISCOVERED THE ERROR AND CORRECTED IT; THE UNICOM OPERATOR ASKED IF MY RADIO WAS WORKING. I ACKNOWLEDGED THAT IT WORKED A LOT BETTER WHEN I HAD IT ON THE CORRECT FREQ. THEN ANOTHER PERSON CAME ON THE RADIO AND ASKED IF I HAD SEEN THEM. THINKING IT WAS THE ACFT THAT WAS SE OF ARPT Y; I SAID 'YES; JUST AS YOU TURNED AWAY FROM US.' THE OTHER CREW TURNED IN AN NMAC RPT. THE ERROR I FEEL WE MADE WAS TO BE ON THE WRONG FREQ INBOUND TO ARPT Y. DISCUSSED THE INCIDENT WITH THE LCL FSDO. HE WANTED TO EMPHASIZE THE IMPORTANCE OF USING THE CORRECT FREQ. I AGREE WITH HIM. IT IS SOMETHING I CONSTANTLY EMPHASIZE ON TRAINING MISSIONS. I WILL CERTAINLY BE MORE AWARE OF MY ACTIONS IN THIS AREA IN THE FUTURE.