GB377067A - Thermionic valve oscillator systems - Google Patents

Abstract

377,067. Valve generating circuits. WIRED RADIO, Inc., 60, Broad.way, New York, U.S.A.-(Assignees of Dow, J. B. ; 37, Oakridge Boulevard, Oakcrest, Alexandria, Virginia, U.S.A.) Nov. 27, 1931, No. 32936. Convention date, July 3. [Class 40 (v).] A tetrode valve oscillator employs three electrodes for the generation of oscillations, and the fourth electrode, which is connected to an output or load circuit, is shielded electrostatically from the other electrodes by earthing, so far as high-frequency is concerned, the adjacent generating electrode. In the form shown in Fig. 1, the inner grid 2 is connected to one end of a coil 8 which may be of tubular or like form, through a condenser 6 shunted by a leak 7. The outer grid is connected through a large condenser 12 to the opposite earthed end of the coil, which is tuned by a condenser 9. The filament cathode 3 carries an oscillatory voltage, and is energized from a battery 13 through a circuit which comprises one-half of the inductance tube 8 and a return wire 14 enclosed by the tube. The anode 5 is connected to the H.T. battery 13a through an output resonant circuit 20 or other impedance, from which voltages may be taken off between the point 21 and earth 22. The tubular coil may be replaced by a wire coil, and the filament current may be returned through a second wire. The earth connection may be made at a point between two blocking condensers shunted across the filament supply source 13, Fig. 2 (not shown). In a modification shown in Fig. 3, the tuned circuit 29, 30 is connected between the cathode 3 and the earthed outer grid 4, and the inner grid circuit includes the grid leak and condenser 6, 7 and a coil 31 coupled to the main tubular coil 29. In Fig. 4, filament current is supplied through choke coils 34, 35, and the tuned circuit includes a split capacity 36 having its middle plate connected to the cathode, one side plate connected to the control grid 2, and the other connected to earth through the grid leak 7 and large condenser 6. The cathode supply 13 is earthed, and the outer grid 4 is effectively earthed through a condenser 12. The circuit arrangements are found to give very slight alterations of frequency when conditions vary in the load circuit, or when the voltage of the source 13a is varied. The load circuit 20 may be tuned to an harmonic of the fundamental frequency.