GB887085A - Improvements in or relating to electric apparatus comprising a thermionic valve - Google Patents

Abstract

887,085. Electrical equipment chassis. GENERAL ELECTRIC CO. Ltd. Aug. 9, 1960 [Aug. 14, 1959], No. 27945/59. Class 37. [Also in Groups XL (b) and XL (c)] In electrical apparatus comprising a thermionic valve and an associated resonant circuit, the resonant circuit comprises a coaxial line shorter than a quarter-wavelength long, the inner and outer of which are short-circuited at one end so that the coaxial line forms the inductive element of the resonant circuit, and the capacitive element is formed by a further conductor encircling and concentric with the outer conductor of the concentric line. As applied to a radio receiver (see Group XL (c)) the coupling between the R.F. and frequency-changing stages comprises a pair of coupled tuned circuits, each of which comprises a short coaxial line, the inner conductor 47, 64, respectively, of which is shortcircuited to and supports the corresponding outer conductor 49, 62, respectively. The resulting inductances are tuned to resonance by the capacities between the outer conductors 49, 62, respectively, and an outer casing 38. In addition, adjustable trimming condensers 19, 25, respectively (Figs. 3, 5), are connected across each circuit, being contained in associated screening chambers 43, 143. The two tuned circuits are coupled together by means of a capacitive probe 60 connected to the conductor 62 and extending within the conductor 49. The inner conductor 47 contains the R.F. amplifying valve 2 which is of the disc seal type with its anode disc clamped between the inner, 47, and outer, 49, conductors. The valve is in grounded grid connection and the cathode circuit components are contained in a screening chamber 39. The inner conductor 47 is supported from the partition 55 by a flange 54, a disc 56 of insulating material being interposed so that H.T. can be fed to the anode of the valve over a choke contained in a recess in the partition 55 (Fig. 4, not shown). The frequency-changer comprises a crystal diode 30 and together with associated circuit components, is contained within the screening chamber 42 ; it is coupled to the inductance 62, 64 by means of a coupling loop 69 extending within that inductance.