[RupertSalt]

By the time I started staying up late, it seemed that most United States-based stations didn't "sign off" much at all.

However, the "border blaster" stations in Mexico would sign off precisely on schedule, playing the Mexican National Anthem [audio] with men's chorus and brass band.

The radio stations were required to broadcast "The Mexican National Hour" in the Spanish language, which turned Sunday evenings into a series of special-programming blocks.