Low noise and distortion audio multiplexing equipment with high stability carrier

THE EQUIPMENT DESCRIBED in this article was the result of conclusions reached while contemplating the problem of how best to utilize the 30-kc “Audio” spectrum offered by the Type-FB microwave radio equipment. The market for the radio equipment primarily was to be in the electrical utility field. It was proposed as especially suitable for providing telephone, telemetering, load-frequency control, supervisory control, and similar communication circuits over distances up to about 50 miles. It was recognized that with microwave radio, the terrain would be a control factor in the maximum length of a radio circuit without repeater stations. A need exists for a communication facility of multicircuit capacity for such distances, both because of the growing congestion of the power-line carrier frequency spectrum and because of the increasing difficulty of applying carrier to the shorter power lines.