Automatic Tuning Techniques for Single-Sideband Equipment

Methods of automatically positioning tuned circuits for rapid frequency changes are discussed. Equipment ranging from low level single-sideband exciter-receivers to high power linear rf amplifiers are considered with attention given to the correlation of positioning accuracy, tuning change time, and ultimate cost of equipment. The merits and limitations of mechanical positioning, follow-up potentiometer servo systems, and phase servo systems, are noted. Special emphasis is placed upon the adjustment of tank circuits in linear power amplifiers. The problem of obtaining phase information for the servo systems is presented and several improved circuits for tuning and loading detection are explained. The paper is concluded with a general discussion of gain control, sequencing of control circuits, and protection of tubes during tuning cycles.