Experimental Ultra-High-Frequency Multiplex Broadcasting System

A definite indication that the need for broadcast facilities in the near future will far exceed the available channels is recognized. A feasible expansion appears to be in the ultra-high-frequency spectrum. To produce the maximum number of channels at ultra-high frequencies, a multiplex system of broadcasting has many advantages: A large number of broadcast programs are transmitted at an assigned frequency from a single location and using only one transmitter and antenna system. Effective use is thus made of an optimum transmitting site, a considerable advantage at very- and ultra-high frequencies where line-of-sight limitation of transmission exists. An experimental eight-channel high-fidelity multiplex broadcasting system has been developed and operated during the past year. Multiplex operation is achieved by time-sharing pulse-time modulation. The operating frequency is 930 Mc. The discussion includes a description and operating characteristics of the major components, including modulator, transmitter-antenna system, and receiver.