Abstract: Apparatus is disclosed for rotating the polarization of microwave signal received into a circular waveguide. This apparatus includes a septum mounted within a waveguide, with that septum including a plurality of discrete interlinked elements mounted to a shaft supported longitudinally of the axis of the waveguide and includes apparatus for rotating adjacent elements angularly about the shaft along with structure for restricting the relative angular rotation of adjacent such elements about the shaft so that the maximum rotation of each element relative to an adjacent element is limited to a predetermined angle for that element.