I believe it's a coastal thing -- WFAN is the only 660 east of the Mississippi. When I worked for 1180 WHAM in Rochester, which is a clear channel station, we'd occasionally get word of interference from a Cuban station that would block our signal in the southern states, but most nights, it was clear as a bell just about anywhere. Yes, it's 50,000 watts, and yes, the AM signal is clearer at night because of the way it bounces off the atmosphere; that's also why it travels farther than FM.