WT4 Millimeter Waveguide System: Field Evaluation Test - Transmission Medium Achievements

The WT4 millimeter waveguide transmission system is a long-haul, high-capacity digital transmission system. In order to prove-in the various manufacturing, installation, and maintenance procedures of the 2157 2158 THE BELL SYSTEM TECHNICAL JOURNAL, DECEMBER 1977 WT4 system, a 14-km length of WT4 millimeter waveguide was installed in Northern New Jersey and tested during the WT4 AT&T field evaluation test. The waveguide is supported on spring supports inside a protective sheath. The waveguide was inserted into the previously installed sheath in several sections, called "pushes." 1 The route, as shown in Fig. 1, began at the Long Lines main station in Netcong and terminated at a temporary facility, Test Station A, in Long Valley, N.J. Two intermediate manholes, which were required to support the transmission medium measurements, were located at approximately 0.4 km and 8.6 km from the Netcong main station. The manholes would not be required for a commercial WT4 system. A variety of route features, typical of those expected for future installations, were encountered along the rightof-way, some of which are listed below: Push 1, mode filter section 1--steep grade and plan bends. Push 4, mode filter section 6--Route 206 road crossing. Pushes 4 and 5, mode filter sections 8 and 9--plan bends and swampy areas. Push 7, mode filter section 14--severe profile bends in part due to a stream crossing. Push 8, mode filter section 17--wet area and plan bends. The installed WT4 transmission medium consists of 60 mm diameter dielectric-lined circular waveguide with one 9-m-long helix waveguide mode filter for approximately every 800 m of dielectric-lined waveguide.