AM radio waves can bounce of the Ionosphere at night. During the day those signals get lost in the static produced by the sun. I remember many nights in the late 60s and early 70s listening to Beaker Street with Clyde Clifford on KAAY out of Little Rock Arkansas. They were allowed to increase signal strength at night to 50,000 watts. The local station broadcasting at about the same frequency signed off at 10PM. I plowed snow many nights in the winter and it was one of the few stations on at night in that era.