Public radio station KLON-FM (88.1) has launched am experimental "Quiet Campaign" for its on-air fund-raiser, which is running through Feb. 28. The KLON idea is to air brief announcements, usually one or two minutes in length during each hour of programming. The messages feature musicians, public officials and current members. "We thought many of our listeners simply will not respond to the traditional membership drive," said Russ Olevsky, the station's membership director. "The messages are quiet, but the response is picking up nicely. We're not sure how this is going to wind up doing--this is an experiment, after all."