New Methods of Frequency Control Employing Long Lines

The practical difficulties encountered in commercial operation of short-wave transmitters, due to the great number of radio-frequency stages required for crystal control, are summarized. The objections to crystal control for some transmitters operated on frequencies above 35,000 kilocycles are given. Methods are described for meeting these objections through frequency control by long radio-frequency transmission lines, which have inherently large volt-ampere capacity and which make possible a considerable reduction in operating costs and improvement in reliability. Methods for applying the lines to the control of oscillator frequencies by using them as relatively constant low power factor resonant circuits and as aperiodic means for feeding regenerative energy from anode circuits to grid circuits are described. A method is given for obtaining both the advantages of crystal oscillators as frequency standards and the economies and reliability of long line transmitter frequency control. Applications of the methods described to experimental and commercial transmitters are mentioned.