The conditions for producing distortionless complete plate modulation of triode radic frequency amplifiers are analyzed. It is shown that the only ay of meeting these conditions is to modulate the grid excitation voltage and the bias potential of the triode amplifier together with the plate supply potential. Calculations made on triodes of different amplification faetors and power ratings by the point-to-point method confirm the analysis. Comparison with modulation characteristies obtained by conventional method shows the distinet superiority of the present system.