FDM/FM 3,600 CH RADIO-RELAY SYSTEMS IN 4 GHz AND 5 GHz BAND.

Large capacity FDM/fm systems with the highest frequency utilization efficienty in the world operating in 4 GHz and 5 GHz bands have been developed. These systems, called SF-B8(4GHz) and SF-E2 (5GHz), respectively, convey 3600 telephone channels per one rf carrier. Increase in adjacent channel interference noise due to spectrum overlapping is overcome by improvement in orthogonal polarization discrimination(XPD) for antenna and feeder systems. Thermal and intermodulation noise is reduced by adopting a low noise amplifier and a delay equalizer in the radio frequency band, respectively. Operational tests started in October 1978 and were successfully finished in December 1979, between Himeji and Hiroshima (SF-B8) and between Tokyo and Osaka (SF-E2).