GB139640A - Improvements in and relating to wireless signalling systems - Google Patents

Abstract

139,640. British Thomson - Houston Co., (General Electric Co.). March 26, 1919. Electric oscillations, producing.-A thermionic oscillation-generator is connected to an aerial in such a way that the capacity of the aerial is' compensated. In systems in which the generator is connected direct to the aerial, the ratio of the. inductance and capacity in the generator circuits is, for a given tuning, largely determined by the capacity of the aerial; but, by the present arrangement, this ratio may be adjusted to the value at which the oscillator works most efficiently. The filament 2 of the oscillator is connected to the grounded mid-point of an inductance 7, and the plate 3 and grid 4 are connected to opposite sides of the same inductance, which acts as a coupling between the grid and plate circuits. The aerial 5 is connected to the plate side of the inductance 7, and its capacity, which may be represented by an imaginary condenser 16, is compensated by a corresponding condenser 17 connected across the grid side of the inductance 7. The plate circuit is tuned by a condenser 9, and the direct-current supply circuit includes a choke-coil 19 designed to be resonant to the oscillation frequency so as to act as a substantially infinite impedance to the oscillations. For telephony, the grid circuit is controlled by a microphone through an audio-frequency transformer 21, Fig. 2, the secondary of which is shunted by a condenser which passes the oscillations, and an audio-frequency chokecoil 23 is included in the direct-current supply circuit.