Linear Plate Modulation of Triode Radio-Frequency Amplifiers

An analysis of the conditions to produce linear complete plate modulation of triode radio-frequency amplifiers shows that the grid-excitation voltage and bias potential of triode amplifiers have to be modulated together with the plate-supply potential. Besides giving linear modulation characteristics, the redected impedance of the radio-frequency amplifier to the modulator is a constant resistance in the present scheme and excessive grid dissipation at the trough of modulation is eliminated. Calculations using the point-to-point method on different triodes and experimental measurements made on the triode 801 agree very well with the theory.