High lights

Radiobroadcasting. Although radiobroadcasting stations in the United States operate on frequencies assigned so as to provide service to listeners throughout the country, practical limitations make impossible good reception on every one of the 100 frequency channels in the band of medium wave lengths for any one listener (pages 666–70). Frequencies of 30 or more megacycles per second have certain characteristics that make them particularly suitable for local broadcasting, and essential for television with present standards, but working frequencies in this region by no means are unlimited. Because such waves are limited in range almost to optical paths, they are unlikely to replace the medium-frequency waves now used for broadcasting over large areas (pages 662–6).