Abstract: A four port magic tee device has three ports defined by an H arm and two parallel side arms which meet at a common junction of the device, and has a fourth (E) port at the junction. Extending over the fourth port is a section of waveguide which acts as a coupling and matching structure by providing a chamber which is coupled to that port. That arrangement enables the E arm of the magic tee device to be reduced to zero length, if desired. In contrast, the E arm of a conventional magic tee of comparable performance must be of some finite length.