As different as they are, these public radio outposts share a carefully tuned appropriateness of structure. There’s the young two-transmitter operation on the Massachusetts shore. Dotted along Alaska’s southeastern panhandle, there are five little stations that survived the contraction of the state’s oil economy. And there are nearly 30 outlets of Minnesota Public Radio that connect small outstate burgs with the rich resources of a big state and the Twin Cities. Station operators say their structures handle functions locally that should be done locally, while relying on parent or sister stations to do other jobs that benefit from economies of scale.