Patent GB-609511-A (GB)
Title: Electrical apparatus including frequency determining tuning means
IPC: H03B5/18
Filed: 1946-01-31
Abstract: 609,511. Electric-heating. WESTERN ELECTRIC CO., Inc. Jan. 31, 1946, Nos. 3175 and 3176. Convention dates, Feb. 1, 1945. [Class 39(iii)] [Also in Groups XIII, XXXV, XL (a) and XL(c)] An arrangement for controlling the tuning of the resonator of a reflex velocity modulation tube .comprises a thermal responsive element 106, Fig. 1, mechanically coupled to the flexible wall 105 of the resonator and bombarded by an electron beam from a cathode 107, and the bombardment is controlled by varying the potential between the members 106, 107 or by varying the potential on a grid member disposed between them so as to determine the temperature of the thermal responsive member 106 and hence the position of the flexible wall 105 of the resonator. The movement of the thermally responsive member 106 may be transmitted to the flexible wall 105 by one or two elastic bows 108, which may be of an iron-cobalt-nickel alloy and may be plated with copper to improve the heat dissipation; the thermally responsive member 106 may be coated with zirconium which increases the heat dissipation and also acts as a getter. In one practical form, Fig. 4, only one bow 67 is used. The thermally responsive member 53, preferably of stainless steel, is channel-shaped, and the electron bombardment is controlled by a grid 60 of flattened helical form; a pair of rods or wires 62 are connected to the cathode by a strip 63 and serve as a focussing or suppressor electrode. The bow 67 is laminated and moves the flexible resonator wall through a crosspiece 68, a pair of rods 69, and a dish-shaped member mounted on the flexible resonator wall itself. The flexible wall may be radially slotted to distribute the stresses uniformly. The cathodes of the tuning unit and of the oscillator portion of the valve are both indirectly heated and the two heater filaments may be in parallel. In a modified arrangement, Fig. 7, a control electrode 269 surrounds the thermally responsive member 252 and the cathode 267; the member 252 is fixed at its upper end. The reflector electrode is mechanically coupled to the flexible diaphragm so that its spacing from the diaphragm is always the same. The oscillatory energy output from the resonator is taken from a wave guide means forming a choke joint being provided to prevent loss of energy at the region of the envelope. Two filaments coated with gettering material are provided which are flashed during the evacuation of the device. Any of the arrangements described may be used in an automatic frequency controlled oscillator arrangement, part of the oscillator output being fed into a discriminator to convert any frequency deviation into a voltage of appropriate sign which is used to control the electron bombardment of the thermally responsive member and so to correct the frequency. The oscillation frequency of the arrangement may be the difference frequency of two local oscillators, an independently variable frequency oscillator being provided for " tracking "; the complete arrangement being a heterodyne receiver-transmitter. The Specification as open to inspection under Sect. 91 states in addition that the invention may be used to tune one of the resonators of a velocity modulation tube described in U.S.A. Specification 2,242,275, or the resonator of a device described in Specification 516,750, [Group XL]. This subject-matter does not appear in the Specification as accepted.