I understand but my question is about our comm radios and line of sight. a few weeks ago I arrived at an uncontrolled airport with multiple runways. The wind was variable but from the north and I landed on 02 along with other traffic. I departed appox. 30 min later. the awos was calling the wind variable but what wind there was, was from the north. There was no traffic in the pattern. I taxied to the end of 02 for takeoff to the north. There are hangers to the west and you cannot see the western half of the east west runway. I'm thinking someone left the hangers as he didn't leave from the fbo while i was there, and taxied to the western end of the runway. I transmitted that I was taking off on 02 and would be departing to the north. On takeoff when crossing the east west runway my RV and a Cessna taking off to the east came closer than I like to becoming intimate. If he broadcast his intensions, I didn't hear it and he obviously didn't hear me. I don't know if he was talking or not but that's where the question is coming from. Without a repeater of some type at a location visible to both aircraft when on the ground how would we hear each other if the radios are truly line of sight. In the future at uncontrolled airports I'm going to take overall visibility of runways into consideration and not solely wind direction.