Research models of helix waveguides

A satisfactory technique of constructing research models of helix waveguides has been evolved. A helix of insulated copper win is wound on a mandrel and surrounded by a sheath of lossy material which, in turn, is covered by an outer plastic jacket reinforced with fiberglass. Units with 2-inch inside diameters hare been made in lengths of 18 ami 112 inches with observed circular-electric-wave losses 90 per cent above theory for an ideal copper tube at 55,000 mc. In short lengths, the. helix waveguide provides a useful component known as a mode filter which may be inserted at intervals in a solid-wall waveguide transmission line. The long lengths are of interest in producing an all-helix waveguide, which is expected to have superior transmission properties.