GB586167A - Tunable ultra-high-frequency apparatus - Google Patents

Abstract

586,167. Electric resonators. HAZELTINE CORPORATION. Aug. 8, 1944, No. 15100. Convention date, Sept. 25, 1943. [Class 40 (iii)] Two sections of transmission line, which may either be #/4 and #/2 long respectively, or be tuned to different frequencies, are tuned by the same displacement of a tuning bridge, and one of the sections is dielectrically loaded so that its frequency may bear a constant relation to that of the other throughout the range of tuning. In a Hartley oscillator, Fig. 1, the upper resonator 12, 13 is connected at one end between the control grid and anode of a valve 10 and is short-circuited at a distance #/4 from the valve by the capacitance between plates 14, 15. These plates are separated by a mica strip 17 and are mounted in a yoke 16 made of thermoplastic resin or the like, so that tuning can be effected by turning the screw 33. The lower resonator 21, 22 is connected to the cathode of the valve and is tuned by a similar short-circuiting capacitance 23, 24, 25, but in order that its electrical length may be extended to #/2 it is immersed in a fluid dielectric, such as castor oil, in a container 30. It is grounded to the container through a brush 29. The residual lengths of the resonant sections, beyond the short-circuits, are detuned by condensers 18, 28. To allow for the difference between the terminating impedances at the valve end (viz. the interelectrode impedance Cgp and the impedance of the cathode) the short-circuits are spaced apart by means of an adjustable member 26, or alternatively compensation may be effected by shunting the open end of the line 21, 22 with a suitable impedance. The cathode-heating battery A, anode battery B and grid leak 32 are connected to the valve through the resonant sections. Instead of the liquid dielectric,. capacitors uniformly spaced along the line 21, 22 may be used for loading it, Fig. 3 (not shown). The frequencies of the two resonators may be equal, as in the oscillator shown in Fig. 1, or be separated by a constant difference. The Lecher lines may be replaced by coaxial lines of which one contains a liquid dielectric such as oil. The short-circuited sections may be replaced by open-circuited sections of appropriate length.