The evolution of the Soviet radio-relay communication systems

Radio-relay communication is a form of radio communication, implemented through the chain of receiving and transmitting stations, usually separated from each other by the sight of their antennas. Radio-relay communication is used for multi-channel transmission of telephone, telegraph and television signals. According to its technical capabilities, number of transmitted messages, range and stability, radio relay lines did not concede to even coaxial cable lines. In the longer distances, terrain and topography of the country radio relay lines were widely used. They could be built in difficult terrains: mountain areas, taiga, over water obstacles, in deserts, etc. The extensive development of radio-relay communications of direct visibility in the USSR began after the introduction of the production of radio-relay systems R-60/120 and R-600 ("Vesna" ("Spring")). On their basis in 1958-1967 an extensive network of radio-relay links was established that provided a large part of the USSR territory with the Central TV studio programs. Successors of lamp systems R-60/120 and R-600, the first generation of radio-relay equipment, were high-capacity long-haul systems ''Druzhba'' ("Friendship") and ''Voskhod'' ("Sunrise"). Being developed in the first phase mainly as a means of delivery of television programs, the network of radio-relay links was more and more used for transmitting the signals of multi-line phones, including all secondary multiplexing (tone telegraph, photo telegraphy, etc.), and transfer of broadcast signals on the combined telephone channels and newspaper texts by the photoelectric method for secondary paths. A qualitatively new stage in the development of radio-relay communication was the development in the mid-1970s of ''KURS'' ("Course") - a set of unified radio-relay communication systems. The last Soviet development for the trunk radio-relay systems was the establishment of ''Raduga'' ("Rainbow") set. Radio-relay communications of direct visibility (with the maximum distance of 40 km without repeaters) could provide the connection neither the Far North nor the remote areas of Siberia. Repeater stations required the creation of an infrastructure necessary for life support of the staff. In these circumstances tropospheric (over-the-horizon) communication lines were created with the distances between places of hundreds of kilometers. Tropospheric communication used the effect of radio wave scattering at inhomogeneities (sporadic layers) of the atmosphere. The appearance in the late 1960s - early 1970s of satellite connections and their wide application since the 1980s, and a significant reduction of the cost of building radio-relay communication systems of direct visibility have significantly reduced the area of tropospheric communication use.

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