GB513679A - Improvements in or relating to electrical oscillation generators - Google Patents

Abstract

513,679. Thermionic valve circuits ; wireless receivers. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., and RAMSAY, J. F. Feb. 17, 1938, No. 5004. [Class 40 (v)] A remotely-controlled oscillator which may be the local oscillator of a superheterodyne receiver comprises a variable tuning circuit at the remote point associated with the grid circuit of the valve over a length of highfrequency cable the capacity of which forms an element in the tuned circuit. The Figure shows an arrangement in which the grid circuit of the oscillator 1 comprises inductance 8, variable capacity 9, and the capacity of line 16 so that the input to the valve is effectively capacitatively tapped down on its tuned circuit. The grid inductance 8 is coupled to the anode inductance 3<1> connected to the anode by highfrequency cable 14. The anode circuit is preferably resonant at or near the upper frequency of the tuning range. Variable inductance tuning may be used and in place of a single valve a number in cascade may be used with the feedback between output and input. When operation at high frequencies is required the nature of the impedance offered by the high frequency cable will change over the operating range. In this case as described in Specification 493,862 the components may be so dimensioned that the oscillator operates as a resonant line oscillator and the anode circuit be resonanted at or near one end of the frequency range for a mode of oscillation to ensure oscillation on that mode.