Detection by Grid Rectifiction with the High-Vacuum Triode

The theory of detection of small signals by grid rectification with the high-vacuum triode of the 201A type is briefly discussed by means of the mathematical method of Carson. Special attention is given to the grid-leak, grid-condenser arrangement. The relation between the non-linear distortion and the degree of modulation and between the frequency distortion and the grid impedances is discussed. A convenient method is described for experimentally ascertaining the frequency distortion in detection and illustrated by means of the results in a typical case; this distortion is compared with that due to resonance in the r.f. amplifier circuits. A method of securing efficient grid-rectification in the super-heterodyne system is described. The detection coefficients for the 200A alkali-vapor tube are given in an appendix.