GB775851A - Wide range radio frequency tuner - Google Patents

Abstract

775,851. Coaxial cavity resonators. ALLADIN INDUSTRIES, Inc. June 1, 1955 [June 9, 1954], No. 15696/55. Class 40 (8). [Also in Group XL (c)] A wide range (e.g. 54 to 890 Mc/s.) tuner comprises a tuning coil 2 having non-uniform inductance per unit length which forms part of the inner conductor of a coaxial resonator. The coil 2 is preferably printed on an insulating cylinder 3 and is longitudinally movable within a conductive sleeve 16 which protrudes through the end 14 of the resonator 10. The portion of the coil extending into the resonator is capacitively coupled to two spaced sleeves 7, 8 which are, in turn, conductively coupled to the walls of the resonator. Insulation between the sleeve 8 and the coil 2 is provided either by an air gap or by a coating of insulant on the coil or the inside of the sleeve. Energy may be coupled to the tuner either by a further sleeve 21 around the coil 2 or by a loop 25. At the lower end of the frequency range the coil 2 is in its extreme left-hand position with the portion 6 of maximum turns density situated between the sleeves 7, 8. The resonant frequency is determined by the inductance between the sleeves. An increase in frequency is obtained by moving the coil to the right. As the frequency increases the coaxial cavity becomes effective as a resonator loaded by the capacitance existing between the coil 2 and the sleeve 7. A conductive tongue 18 on the end of the coil 2 ensures that this capacitance gradually decreases as the coil is moved further to the right. The initial capacitance between the sleeves 7 and 8 may be adjusted by means of a sliding conductive tube 28 guided by an inner tube 22 of insulating material. In a modification, Fig. 8, the sleeve 16 is capacitively coupled to the end wall 14 of the resonator. For this purpose the sleeve is provided with a flange 86 spaced from the end wall by means of insulating screws 87. A sheet 88 of mica acts as a dielectric and prevents contact between the sleeve and the resonator wall. A sleeve 89 envelopes the portion of the coil 2 outside the resonator. Transfer of energy to and from the resonator is effected by connections between a lead 90 to the flange 86 and the wall of the resonator.