Abstract: Coaxial units are disclosed for coupling an r.f. amplifying microstrip to splitter and combiner wave guides, respectively, of a splitter-combiner apparatus. Each coaxial unit comprises an outer conductor sleeve and an inner conductor pin projecting forward of the sleeve, both the sleeve and pin having forward portions which are resiliently compressible radially inward, and the sleeve being radially enlarged at its front end. The coaxial unit is coupled at its front to its associated wave guide by having its sleeve and pin forward portions, respectively, received in, and radially inwardly compressed in, large and small bores respectively formed in the metallic plates on opposite sides of the dielectric chamber of the associated wave guide. Those forward portions make direct yieldable-pressure electrical contacts with metallic walls of these bores at locations adjacent to the openings of such bores into that chamber.