A combiner/divider includes a transition waveguide interposed between a plurality of input/output waveguides and an output/input waveguide. The input/output waveguides are preferably distributed in a radial sector extending in the E-plane of the input/output waveguides. The input/output waveguides extend from inner nodes disposed proximate to and spaced from a sector center to outer nodes disposed along an arc of the sector. At least some of the input/output waveguides taper in size from the inner nodes to the outer nodes. Walls between adjacent input/output waveguides also may taper in width between the inner nodes and the outer nodes. The output/input waveguide has an inner port facing and spaced from the inner nodes of the input/output waveguides. A transition waveguide extends between the input/output waveguides and the output/input waveguide and has side walls extending along the radii of the sector for communicatively coupling the output/input waveguide with input/output waveguides.