An ortho-mode transducer may include a cylindrical common waveguide terminating in a common port, a rectangular vertical branch waveguide in-line with the cylindrical common waveguide and terminating in a vertical port, and a rectangular horizontal branch waveguide normal to the common waveguide and terminating in a horizontal port. The vertical branch waveguide may be configured to couple a first linearly polarized mode from the vertical port to the common waveguide. The horizontal branch waveguide may be configured to couple a second linearly polarized mode, orthogonal to the first linearly polarized mode, from the horizontal port to the common waveguide. A portion of the vertical branch waveguide may overlap a portion of the cylindrical common waveguide. A septum may span the vertical branch waveguide proximate to the overlapping portions of the vertical branch waveguide and the common waveguide. A rectangular symmetry cavity may be opposed to the horizontal branch waveguide.