Patent GB-772839-A (GB)
Title: Improvements in frequency selectors for receiving individual frequencies in the v.h.f. bands
IPC: H03J5/00
Filed: 1953-09-08
Abstract: 772,839. Radio receiving apparatus. STANDARD COIL PRODUCTS CO., Inc. Sept. 8, 1953 [Nov. 26, 1952], No. 24832/53. Class 40(5) A tuner for tuning a television receiver to any one of a plurality of channels in the V.H.F. band comprises a rotatable turret 10 composed of a plurality of panels carrying contacts which selectively cooperate with fixed contacts on the stationary portion of the tuner, the co-operation of any one panel with the fixed contacts conditioning the receiver to receive any one of a plurality of channels within a relatively narrow band, final selection being achieved by rotation of a shaft carrying a plurality of dielectric plates which cooperate with capacitor plates mounted upon and upwardly from the panels to determine the tunings of the panels over their respective relatively narrow bands. In the arrangement described the U.H.F. turret 10 is associated with a further 12- position turret 180, similar to that described in U.S.A. Specification 2,496,183, used for tuning the receiver to channels within the V.H.F. range. The turret 10 is rotated by means of a hollow shaft 16 through which passes a shaft 25 to which the V.H.F. turret 180 and the dielectric tuning plates are attached. The turret 10 has nine positions in one of which the panel bearing contacts and capacitor plates is replaced by a tie bar, when the turret is set to this position a switch is operated to render the V.H.F. turret operative to receive within the V.H.F. range. When the U.H.F. turret is set to one of the remaining eight positions the circuits associated with the V.H.F. turret are switched to make them function as' two-stage I.F. amplifier to which the LF. output from the U.H.F. turret and its associated circuits is applied. Simultaneously selection of the desired channel is achieved by rotation of shaft 25 to the appropriate one of ten positions, these positions being determined by the indexing mechanism associated with turret 180 and thus corresponding to ten of the twelve possible positions of that turret. Fig. 3 shows the construction of the U.H.F. turret 10 which comprises eight panels 30 and a tie bar 66 mounted between end-discs 11 and 12. The turret is rotated as a whole by shaft 16 which is attached to end/disc 11 and the tuning to individual channels is effected by rotation of shaft 25 upon which are mounted dielectric plates 61, 62 and 63 which co-operate with capacitor plates mounted on the panels 30, the plate 61 and associated capacitor 45 affecting local oscillator tuning, the plate 62' and associated capacitor 46 effecting mixer input tuning and plate 63 and associated capacitor 47 effecting aerial tuning. Earthed shielding plates 54 are placed between the capacitors 45 and 46. Tuning coils 50, 55 and 56 are associated respectively with capacitors 45, 46 and 47. The contacts 35-40 carried by the panels 30 cooperate with contacts 105-110, Fig. 1. In the position of turret 10 shown in Fig. 1 a rod 113 attached to the turret operates upon a switch member 120 to rotate a shaft 162 and thereby lift a set of contacts 190-200 into contact with the contacts on V.H.F. turret 180, the tuner thus being set for V.H.F. reception. In each of the remaining eight positions of the turret 10, the switch member 120 is released and shaft 162 rotates to bring contacts 190-200' into association with a contact assembly 205 whereby the circuits forming the V.H.F. portion of the tuner are altered to operate as a two-stage I.F. amplifier. Finetuning is provided for both the V.H.F. and U.H.F. ranges. Hollow shaft 101, Fig. 1, surrounding shaft 16 carries discs 102 which frictionally engage a quadrant member 103 with which rotates a shaft 104. Shaft 104 carries a shaped dielectric member 450 which co-operates with projecting capacitor plates 452, 453 on the panels 30, these plates comprising extensions of the plates 41a, 41b respectively forming the local-oscillator tuning capacitor 50, Fig. 3. Shaft 104 carries a further shaped dielectric plate (not shown in Fig. 1) which cooperates with a pair of fined capacitor plates for effecting fine tuning in the V.H.F. portion of the tuner, Fig. 10 (not shown). Specifications 720,328 and 733,005 are referred to.