Radio reception is Line of Sight (LOS). The radio waves travel in a straight line and do not bend around the curvature of the earth. At night you get the skybounce affect where the waves will bounce off the ionosphere and reception often is much longer. In a forest or in a city, radio waves are blocked by trees, hills, building, etc, so range is even less. A radio up on a hill with a straight shot to another radio will have pretty good range.