A "Short-Cut" Method for Calculation of Harmonic Distortion in Wave Modulation

Precalculation of harmonic distortion produced by vacuum tubes used in all stages of a class B audio amplifier, for a great variety of operating conditions, is an important item in the work of the radio design engineer. A graphial method for this and similar calculations, which gives considerable saving of time has been developed. It is applicable to all symmetrical periodic curves containing harmonic components plotted to the sine of the fundamental frequency, sin ωt. The procedure consists in connecting the ends of such a curve by a straight line and measuring the ordinate differences between the curve and the chord for five definite values of abscissas. Simple expressions allow, then, for a rapid calculation of harmonic components up to 11th order. The method has proved to be very useful in class B modulator design.