The use of miniature tubes in class C circuits

Receiving-type tubes designed primarily for small-signal class A applications are being used in an increasing number of class C circuits in mobile transmitters and other revenue bearing industrial equipment requiring a high degree of reliability. Tube performance in such circuits is often limited by the effects of class C operation on the individual elements of the tubes. This paper analyzes such effects in the RCA 7054, a miniature sharp-cutoff pentode designed for use as a low-level frequency multiplier in mobile service, and describes circuit-design techniques which can be used to improve equipment reliability.