A New Treatment of Electron Tube Oscillators with Feed-Back Coupling

In an electron tube oscillator with feed-back coupling, the ratio E
g
/E
p
may be expressed as ϵ|i, in which ϵ and Φ are respectively called "excitation" and "phase difference." For the maintenance of self-oscillation it is absolutely necessary to have a correct Φ, and for the optimum intensity of self-oscillation there is usually a most favorable ϵ for a given oscillator. The complex ratio E
g
/E
p
is a function entirely of the constants outside of the tube (i. e., independent of the tube characteristics), provided the grid current and the effect of resistances on the oscillation frequency are assumed negligible. Expressions for E
g
/E
p
are given for several types of oscillators, which are derived from a general oscillator network containing three parallel resonant circuits connecting the plate, grid, and filament. All ordinary oscillators are subderivatives of these types and their expressions for E
g
/E
p
are easily obtained by applying special conditions. Numerical computations have been made for practically all special oscillators and the resulting values for ϵ and Φ are illustrated by curves from which considerable information concerning the operating behaviors of oscillators can be obtained. In a two-mesh oscillator there are two frequencies, at either of which the oscillation may take place. It is shown that only the wave which gives the correct Φ can be excited. Experimental check of the theory has been found quite satisfactory in most cases.