Satellite television distribution: service from geostationary satellites to community antennas in multiple-coverage areas

The first application of satellites for transmitting television to community antennas or for direct broadcasting to the public is likely to be to cover large areas with a single programme. At a later stage, however, it may be concluded that satellites could provide a service similar to that of the existing terrestrial systems, i.e. broadcasting to a large number of small contiguous areas with separate programmes. This presents problems associated with efficient use of the frequency bands which may be available and of the geostationary orbit. The effects of the parameters of the frequency-modulation method assumed, including the interference protection ratios, and of the antenna radiation patterns on these factors, are examined in some detail. From these considerations, an idealised model has been used to obtain generalised expressions, assuming a geometrical arrangement of the coverage areas. Where applicable, these have been used to determine the powers, bandwidths and orbital separations of the satellites serving a typical area such as Europe. It is shown that, for domestic reception via community antennas, four programmes could be provided to each of 30 countries, using eight satellites in 20° of orbital are. A bandwidth allocation of 400MHz at a frequency in the region of 12GHz has been assumed. Direct reception at domestic receivers would require greater satellite transmitter power than community reception, and the orbital are required would be approximately 35°.