Oscillating Audion Circuits

A general method is presented for investigating theoretically the conditions of oscillation in circuits supplied by an audion. This method is based on the relay action of the audion, as represented by its characteristic curve, and has for its fundamental idea the use of the slope of this curve as a physical constant of the audion, called the "mutual conductance." Two modes of applying this method are given: the simple, but approximate, "loss method" and the exact "complex method." Various particular circuits are discussed and formulas given for the natural frequency and the required value of mutual conductance to maintain an oscillation. These circuits include the elements of all the common oscillating audion circuits depending on the relay action; so it is seen that the actions in these various circuits are not distinct and independent, but are here brought under a single set of physical ideas. The circuits chosen for detailed discussion are those which most simply illustrate the method of treatment and which exhibit the various useful properties that may be obtained with different connections of the audion. It would be impossible to include in any paper of reasonable length a discussion of, or even a reference to, all the possible oscillating-current circuits that may have practical application. The behavior of certain circuits toward impressed oscillations (as from an antenna) at various frequencies is considered.