GB261905A - Improvements in and relating to thermionic valve wave-meters and the like - Google Patents

Abstract

261,905. Edgeworth, K. E. Nov. 13, 1925. Thermionic valve circuits. - In a wavemeter or frequency meter, the grid and anode circuits of the valve are connected across a small number of turns only of the tuning inductance, or equivalent inductive couplings are employed, thereby rendering the calibration sensibly independent of the capacity of the valve. In the example shown in Fig. 1 the oscillatory circuit comprises a tuning inductance 4, having nine turns, and a variable condenser 5. One end of the inductance 4 is connected to the high-tension battery, and the anode 1 of the valve is connected to the third turn from this end. The untuned grid coil 6 may consist of three turns with a tight coupling or a somewhat larger number with a loose coupling. In a modification, Fig. 2, the grid 2 is connected to the third turn from the end of the inductance 4, the untuned anode coil 7 consisting of three turns with a tight coupling or more with a loose coupling. The effect in each case is to reduce the equivalent capacity added to the oscillatory circuit by the valve, which equivalent capacity is approximately proportional to the square of the number of turns across which the valve is connected. The damping of the oscillatory circuit should be as low as possible. Accord. ing to the Provisional Specification the invention may be applied to wavelength standards or for generating local oscillations for heterodyne reception.