Flight Crew Private
Flight Crew Last 90 Days 3; Flight Crew Total 305; Flight Crew Type 5
Conflict NMAC
Flight Crew Took Evasive Action
Aircraft; Human Factors
Tuned radio to frequency while approaching ZZZ airport from the west.  I listened for traffic at ZZZ and announced intentions to land on Runway XY after crossing midfield Runway XY-YX.  These announcements were 10 miles and again 4 miles west of the airport.  Crossed midfield from the west; made right turn to the south to enter Runway XY from 45 degrees. Announced again on frequency entering left downwind Runway XY; announced base; then final for Runway XY.  Saw that I was high and went around.  At midfield; while departing and at about 100-200 feet AGL; I saw another aircraft approaching from straight ahead and about 75 feet above me and to the left.  The opposing aircraft banked right; as did I. The other aircraft must have been landing on Runway YX and was also going around; because I did not see an aircraft on the runway or taxiway as I approached.  I checked the airport traffic CTAF against my entered radio frequency and saw the correct frequency was frequency.  I had been announcing on frequency and did not realize I was on the wrong frequency. I had made an error in tuning radio and did not hear the airport traffic; nor did they hear me and my announcements.
RV-7 pilot reported tuning the wrong CTAF frequency at an uncontrolled airport resulting in an NMAC.