Interesting, 27.525 MHz AM is one of the more popular trucker out of band (freeband 11m) frequencies, but you could be hearing stations local to you. I've noticed lots of AM voice traffic in the 27.405 to 28.000 MHz region during the recent 11 meter band openings. 27.525 MHz, 27.545 MHz, 27.575 MHz, 27.585 MHz, 27.605 MHz, 27.615 MHz, 27.635 MHz and several others have been active. The other day 27.845 MHz, 27.775 MHz, 27.725 MHz and 27.885 MHz were also active with AM voice traffic.