The Construction and Motion Characteristics of the Telecommunication Relay Float

ABSTRACT Nippon Telegraph and Telephone Public Corporation proposed a new ocean microwave system using a floating station. The floating station is a spar buoy moored by four series of chains and sinkers, on the end of the continental shelf. It connects deep sea submarine cable systems with ocean microwave systems by which signals from submarine cable is landed. The submarine cable troubles which occurred on the continental shelf can be avoided by using it. Before the design, construction and installing ocean operation of it, several studies, model experiments and investigations were performed. The station was installed on the sea 17 N.M. south east of Is Peninsula in the summer of 1973. It is now operating as an experimental microwave station. Also it has not experienced a strong storm, observed maximum pitching or rolling is 5 degrees with a period of one minute. Little fading of the microwave signals are observed. The purpose of the system, construction of the station, fundamental investigations of buoy and the process of the ocean operation of its installation will be reported. PREFACE Nippon Telegraph and Telephone Public Corporation suggested ocean communication systems by floating stations. The system is intended to assure the high reliability of the conventional submarine coaxial cable system in shallower waters where its various obstacles have been inherently caused by human activities such as fishing. Microwaves radiated from the new system travel over the shallow waters, and reach to the highly reliable submarine coaxial cable system laid in the deep water free from any obstacles through the floating station, as a relaying point, installed on the edge of a continental shelf. Fig. 1 shows a concept of this system. In order to realize the over-sea microwave communication system utilizing the over-sea path, the development of an automatic tracing method by the antenna system, the tracking method and the radio equipment as well as the designing of such a floating station of less motion are necessary. We have been studying these since 1968. In 1968, the committee of floating station (Chairman Takuji Ohe) was established in the Japan Ships Machinery Development Association to 'ascertain its efficiency. In the next year, tank tests and wind tunnel tests using scaled models were performed to ensure its motion performance. As a result of the tests, an vertical cylinder type of floating station of 135 m in length was selected. This type of station to be moored to the sea bottom has proved not to exceed the fixed allowance of movement under the worst sea conditions, and it became clear that such a floating station could be put into practical use. As a result of another study on the over sea microwave communication system carried out together with the above tests, effective countermeasures against fading and propagation distortion of the over-sea path, such as diversity effect for better performance, construction of antenna system and communication equipment suitable for directional control, and tracking method of incoming waves, etc., were successfully boiled down to the completion of its design. As described above, the over sea communication system have been assured of its realization through such progress. Since the over-sea microwave line utilizing this type of marine structure is unprecedented in the world, additional experiments were planned by the use of actual structure to confirm the motion characteristics of the floating station as well as its efficiency as a system.