Patent GB-375831-A (GB)
Title: Improvements in wireless receivers, amplifiers and the like
IPC: H04B1/30
Filed: 1930-12-29
Abstract: 375,831. Valve circuits. WALTON, G. W., 2, Dean Street, London. Dec. 29, 1930, No. 39071. [Class 40 (v).] In wireless receivers or amplifiers, local oscillations at a frequency equal to the signal frequency are applied to a non-oscillatory input circuit of a valve in such manner, that (i) the losses in that circuit are made good by the local oscillations, which are applied in phase opposition to the signal oscillations ; (ii) the potentials due to the local oscillation in the input and output circuits balance when no signal is received ; (iii) reception of a signal reduces the oscillatory potential of the input circuit and thereby produces oscillations in the output circuit. Local oscillations from 7, Fig. 1, are applied to the grid and anode circuits of the valve 1 across the impedance 6 so that with no signal from 13 there is no oscillation in the output coil 4. The grid circuit 12, 13 is aperiodic and has high damping by resistance or other means. Feed-back from the coil 3 only occurs when a signal is received and further reduces the oscillatory potential applied to the grid from 7 by assisting the signal oscillations which are of the fame frequency and of opposite phase. The battery 5 may be dispensed with by employing the arrangement of Fig. 3, in which the signal is simultaneously applied to the grid circuits 12, 12a, of a pair of symmetrically connected valves 1, 1a, with signal input 13, outpu from 4, 4a, 4b and local frequency applied from 7 across impedance 6. Valves arranged as in Fig. 1 may be connected in cascade, Fig. 4 (not shown). A detector circuit for use with the invention is shown in Fig. 6, in which 28 is an anode-bend detector with an impedance 32 in the grid circuit across which the local oscillations are applied from 33. It is stated that with such an arrangement, the rectifier is fully loaded with low frequency only and low frequency stages may be dispensed with by choosing a valve of the required power output. A full wave rectifier on the same principle as Fig. 6 is constituted by a pair of valves on push-pull, Fig. 8 (not shown). The frequency of the local oscillation is kept equal to the incoming oscillation frequency by a method shown in Fig. 9, comprising a triode oscillator 56, in which the gridanode coupling is a tuned circuit 58, 59, 60. Part of the received signal is applied to the grid circuit of the oscillator at 66, 62 and pulls the local oscillation into step if small variations of frequency occur. Fig. 10 shows a complete receiver, a being the local oscillator, b an amplifier and c the detector ; part of the receiving inductance e is included in the oscillator circuit for keeping constant frequency relation as in Fig. 9. Oscillations from a are fed into the anode circuit of b across the impedance j and into the grid circuit through the coupling g. Reaction due to signal voltages fed to b is obtained by coils h. Simultaneous reception of two signal frequencies may be obtained by providing the local oscillator with two tuned circuits resonant to the signal frequencies, a common amplifier and two separate detectors, Fig. 11 (not shown).