Listen for more business programming on AM radio, as entrepreneurs buy troubled stations to experiment with new formats. The decline of AM has made access easier, notes American Radio editor James Duncan, and a specialized format is one way to go. L.A.'s KMNY has 24-hour financial programming, while Florida's WWNN plays nonstop motivational excerpts from the likes of Zig Ziglar. A Boston company, Business News Broadcasting, says it plans to launch an all-business news service for AM radio this fall.