“Radio Nomadica” (alternating Saturdays, 10 to midnight), with host Jeffrey Philpott, debuted January 27. After a break for the community radio station’s February membership drive, Philpott will be back on air Saturday (February 24). “Radio Nomadica” fills the vacancy left by “Night Roots,” commanded for 18 years by the late, beloved Richard Dunk. In this age of musical micro-genres, “Radio Nomadica” has no easy one-word descriptor. For Philpott, radio was a big part of growing up in the Bay Area in the ’70s and ’80s.