GB436940A - Thermionic valve modulation systems - Google Patents

Abstract

436,940. Valve-circuits for wireless reception. HAZELTINE CORPORATION, 15, Exchange Place, Jersey City, New Jersey, U.S.A.-(Assignees of Wheeler, H. A. ; 18, Melbourne Road, Great Neck, New York, U.S.A.) Jan. 18, 1934, No. 35645/33. Convention date, Jan. 30, 1933. [Class 40 (v)] , In a modulating or frequency changing multi-electrode valve-circuit, a virtual cathode comprising an aggregation of electrons is produced between a pair of grids by applying positive potential to the grid nearer the actual cathode and a negative potential to the other grid, the signals being applied to a grid, e.g. the positive grid, between the virtual cathode and anode, and the density of the virtual cathode being periodically varied by local oscillations. In Fig. 1 (not shown), a local source of oscillations is connected to a grid between the actual cathode and the positive grid, but in other arrangements these two grids and the actual cathode form a triode oscillator. The negative potential on the signal grid may be automatically varied to control volume. The Specification describes the operating condition of the valve for producing optimum effects such as independence of the oscillator and modulator sections of the valve. In the frequency changer shown in Fig. 2, the cathode 1 and first and second grids 2, 3 form the oscillator, the cathode 1 being connected to a tapping on the tuned coil 19 of grid 1 to form the coupling between the circuits of grid 1 and the grid 2 which is virtually the anode of the oscillator. The incoming signals are applied to the tuned circuit of outer grid 4 which is relatively close to grid 3, being indicated by dotted line 7. Manual or automatic volume control bias may be applied over terminal 17 to the grid 4 which has variable-mu characteristics, bias variations having substantially no effect on the oscillator portion of the valve. In modifications, Figs. 3 to 9 (not shown), the following features are used alone or in combination (1) separate back coupling coil in the circuit of cathode 1 or grid 3, (2) combined capacitative and inductive feed back which facilitates ganging of condensers 14, 18, (3) a grid leak and condenser for the oscillator grid 2 to develop a negative bias for amplitude and grid current limitation, (4) separate resistance or choke feeds for the high tension to anode 6 and grid 3, (5) a high potential screen between grid 3 and the anode. The Specification also describes complete superheterodyne receivers embodying the above features. Fig. 10 (not shown), employs manual volume control, whereas Fig. 12 (not shown), employs automatic volume control from a diode-triode second detector. Specifications 293,462, [Class 40 (v)], 398,882, and 435,383 are referred to.