previous crimes.On the airCONCORD (AP) — New Hampshire's fourth commercial television station is on the air.WNHT-TV, Channel 21, went on the air Monday morning in Concord, broadcasting from a tower in EpsomThe other New Hampshire stations broadcast from Derry. Channel 50; Manchester, Channel 9; and Hanover, Channel 31.The state also is served by public television, Channel 11, and its repeaters.