Television broadcasting stations

The paper surveys the television transmitting-station distribution scheme by which the B.B.C. hope to provide the greater part of the United Kingdom with a television service using the 405-line 2: 1-interlaced-scanning 25-pictures/sec British Standard transmission. The basic factors underlying the choice of scheme are discussed, together with the arrangements for dividing the available 41¿68 Mc/s frequency band into five separate operating channels using the receiver-attenuation system of vestigial-sideband transmission. The proposals for operating two geographically separated transmitters, one of high power and one of low power, on each channel to complete a 10-station plan, and the precautions needed to minimize co-channel interference, are explained. Some of the problems of site selection for transmitting stations are mentioned, and a brief account is given of propagation phenomena which influence the estimation of service area. The scheme for linking the stations with the London studio centre is briefly described. The general planning and design of the complete transmitting equipment used at the B.B.C.´s new high-power television broadcasting stations and intended for use at the future low-power stations is surveyed, with particular reference to the different types of vision and sound transmitters, monitoring equipment, air and water cooling installations, vision/sound combining circuits, transmission lines and aerial systems, to indicate the progress so far made and illustrate the trend of future developments.