Patent GB-297253-A (GB)
Title: An improved process and apparatus for undisturbed radio-communication
IPC: H04B14/00
Filed: 1927-12-12
Abstract: 297,253. Plebanski, J. Dec. 12, 1927. Addition to 283,190. Modulating systems ; atmospherics ; eliminating ; fading, preventing.-Relates to a transmission system in which modulation is effected by means of phase-shifted sidebands or out-ofphase signalling currents as described in the parent Specification. 'The geometrical orientation of the separately detected currents is produced by a number of symmetrically-arranged fixed coils 1, 2, Fig. 1. which set up a rotary field from which the required signal is fed by an adjustable search-coil a to the input of the receiving valve. In transmission a three-phase generator a, Fig. 10, supplies one phase Oo to an oscillator #, the output of which is modulated, and a second phase #1 to a second oscillator Jc giving an unmodulated output. Or a single-phase exciter may be used in combination with an artificial-line phaseshifter. Alternatively, as shown in Fig. 22, a two-phase alternating current of 50 cycles displaced in phase by 90 can be used to modulate a single carrier wave. By transmitting such an output from a beam or directive aerial, and providing thermionic or ferromagnetic rectifiers in each phase-line #1, #2 of the receiver, the system can be used for the transmission of power through the ether. Or the side band components of a single carrier-wave can be dephased by using a coupling-circuit Z, Fig. 22, comprising inductances, resistances, and capacities which serve to stabilize the phase displacement. The phaseshifting of the sidebands can alternatively be effected by means of a local heterodyne in reception. As shown in Fig. 23, the carrier-wave and two sidebands resulting from a local heterodyne V2 pass through a path B comprising an intermediate-frequency amplifier, whilst the carrier-wave passes through a similar but separate path C, a phase-displacement being imposed upon the latter by means of a suitable network J. In this case fading effects can be compensated by feeding a rectified current, derived from the incoming high-frequency energy through a detector valve G, to the cores of the inductances contained in the network J. When fading occurs, the dephasing effect of the network J upon the signal components is regulated, by controlling the rectified magnetizing current passing through the cores, so as to increase the effective signal strength. Heterodyne reception can also be effected bv utilizing a chord of audible notes corresponding to the beats with the modulated sidebands. There is no heterodyne beat with the carrier wave so that the effects of atmospherics or similar disturbances are cut out. As ordinary transmission is not audible in the receiver two messages can be handled simultaneously on one and the same wave, one message being sent according to the invention, and the other by known methods. By replacing the pick-up coil by a short-circuited rotor, the latter may be caused to actuate directly the diaphragm of a loud-speaker or other form of recorder. The method of modulation ensures a high degree of selectivity in reception, and an economicallydistributed load upon the power circuits in transmission.