GB102500A - Improvements in High Frequency Signalling, particularly applicable to wireless telephony. - Google Patents

Abstract

102,500. Western Electric Co., (Assignees of Kendall, B. W.). Nov. 29, 1915, [Convention date]. Wireless telegraphy and telepliony; electric oscillations, producing.-In a method of receiving signals transmitted by modulated high-frequency waves, particularly applicable for wireless telephony, the received oscillations are combined with locally-generated oscillations of the same frequency. In the system shown in Fig. 1, the aerial circuit is coupled to a local oscillationgenerator 40 and to a secondary circuit 20, 21 connected to an audion or other detector 33. The negative pole of a battery is connected to the grid to reduce or eliminate the current flowing from the filament to the grid. Instead of using a separate generator 40, the audion may be arranged to produce oscillations of the same frequency as the received waves, the necessary coupling between the input and output circuits of the audion being obtained by connecting the filament to a point in the secondary 20, the secondary circuit 20, 21 preferably containing an adjustable resistance by which the strength of the local oscillations is controlled. In the arrangement shown in Fig. 3, the received oscillations are amplified by an audion C before being combined with the oscillations produced by the generator D. The coil 70 is coupled to the coil 20 so as to cause the production of oscillations in the audion D, whereas a coil 67 is coupled to the coil 60 so as to neutralize any tendency of the audion C to generate oscillations owing to electrostatic coupling between the input and output circuits. In the system shown in Fig. 4, the received oscillations are amplified by an audion E before being combined with the oscillations produced by the generator F, the output circuit of which has three parallel paths, the first containing a battery 35 and a high ohmic resistance 80, the second containing a relatively large condenser 81 and the primary 82 of a lowfrequency transformer, whilst the third path contains the condenser 81, a condenser 73 of low capacity, and a coil 70 which couples the input and output circuits. The secondary of the lowfrequency transformer is connected to a non-inductive resistance 84, across part of which is connected the input circuit of an ordinary audion G, the output circuit of which is connected to a telephone transformer 91. The resistances 80, 84 may be of the order of 100,000 ohms.