Waveguide filters using expanded joints

A method of constructing waveguide filters of the type incorporating inductive posts, or pins, so as to provide improved microwave performance avoiding the use of soldering or brazing alloys at the important electrical interfaces within the waveguide structure. Using high conductivity base metals, the method requires only cold-flow expansion to provide highly conducting, or low resistance, joints. Low conductivity base metals may also be used so that application of the construction technique includes both jointing prior to, and/or jointing subsequent to, the surface deposition of a highly conductive metal coating by known means. The pins are bored at their ends, and a member, e.g. a ball (4), of greater hardness and diameter is forced in to expand the tubular end of the pin into good contact with the waveguide wall.