Vacuum Tube Electronics at Ultra-High Frequencies

Vacuum tube electronics are analyzed when the time of flight of the electrons is taken into account. The analysis starts with a known current, which in general consists of direct-current value plus a number of alternating-current components. The velocities of the electrons are associated with corresponding current components, and from these velocities the potential differences are computed, so that the final result may be expressed in the form of an impedance. Applications of the general analysis are made to diodes, triodes with negative grid, and to triodes with positive grid and either negative or positive plate which constitute the Barkhausen type of ultra-high-frequency oscillator. A wavelength range extending from infinity down to only a few centimeters is considered, and it is shown that even in the low-frequency range certain slight modifications should be made in our usual analysis of the negative grid triode. Oscillation conditions for positive grid triodes are indicated, and a brief discussion of the general assumptions made in the theory is appended.