Abstract: Waveguide devices, associated components and methods. Waveguide devices can include a rectangular waveguide having first and second rectangular ports at one end, and first and second circular waveguides extending from opposing broad sides of the waveguide to provide either full isolation or full transmission between first and second ports. The waveguide can include a fixed short at one circular waveguides and a short with adjustable biasing structure at the other circular waveguide to accommodate broader ranges of high-power capabilities. The waveguide device can be stacked by connecting circular waveguides of adjacent structures to provide an isolator with additional ports or an adjustable directional coupler. The adjustable shorting structure can include plunger or screw-type threads.