Orthomode transducers (OMTs) and methods of fabricating OMTs are disclosed. According to disclosed embodiments, an OMT includes a housing defining an internal waveguide. The housing may be composed of a first cast housing member attached to a second cast housing member. The first housing member may include a first side of the waveguide that is cast into the first housing member. The second housing member may include a second side of the waveguide that is cast into the second housing member. A method of fabricating an OMT may include arranging at least one casting insert in at least one mold, casting the housing in the mold and casting a waveguide in the housing using the at least one casting insert. The disclosed devices and methods provide cost effective solutions for fabricating OMTs of various operating frequencies that share a substantially similar outer housing shape and size.