Patent GB-782839-A (GB)
Title: Combination frequency selector
IPC: H03J5/02
Filed: 1954-11-05
Abstract: 782,839. Radio receiving apparatus. STANDARD COIL PRODUCTS CO., Inc. Nov. 5, 1954 [Nov. 18, 1953], No. 32047/54. Class 40 (5). A tuning assembly for selectively tuning to any one of a plurality of television channels in the V.H.F. and U.H.F. range comprises a V.H.F. turret and a U.H.F. turret which latter turret has (a) a first position (the V.H.F. position) wherein each position of the V.H.F. turret selects one of the V.H.F. channels as determined by circuit elements mounted on panels carried by the V.H.F. turret; (b) a plurality of other positions wherein circuit elements mounted on panels carried by the U.H.F. turret select one of a plurality of bands of U.H.F. channels according to the particular position of the U.H.F. turret and tuning to individual channels within the band is effected by tuning elements associated with the circuit elements upon the U.H.F. panel but mounted to move with the V.H.F. turret so that rotation of the V.H.F. turret affects the tuning within each band of the U.H.F. channel and (c) a remaining position in which the circuit elements carried by the V.H.F. turret are effective to select individual channels in a V.H.F. range over part of its rotation and the circuits carried by the corresponding U.H.F. panel are effective to select a band of U.H.F. channels which may be individually tuned by a rotation of the V.H.F. turret over the remainder of its rotation. The object of the invention is to achieve a tuner wherein channel members are selected by a decade operation; since, however, in the system to which the invention relates channel 13 is at V.H.F. whereas channel 14 is at U.H.F., it is necessary, when tuning over the range of channels selected by turning the U.H.F. turret to the " tens position, to provide that the circuitry changes automatically from V.H.F. to U.H.F. channel selection midway through the range. Fig. 2 shows the tuning assembly. The U.H.F. turret 340 comprises a plurality of panels 220, each of which carries circuit elements whereby electrical connection may be made with contacts mounted within the tuner chassis 305. When the turret 340 is turned to the appropriate position tuning to individual U.H.F. channels is effected by rotation of the V.H.F. turret 300, dielectric members mounted on the shaft of the turret 300 and lying within the U.H.F. turret 340 cooperating with capacitor plates carried internally by the corresponding panel 320 to effect the necessary tuning. The signal selected by the U.H.F. turret is heterodyned with a local oscillation generated by valve 248 to produce an I.F. signal which is taken to the V.H.F. portion of the chassis, this portion operating as an I.F. amplifier when the U.H.F. turret is in a position as described. The U.H.F. turret also carries a blank panel 410 and a cam which co-operates with cam follower 480, so that when the U.H.F. turret is turned to a position where the panel 410 engages with the fixed contacts carried by the U.H.F. portion of the chassis 305, the cam follower 480 moves, causing contacts 428 to move from an upper to a lower position in which they are disconnected from the circuits which caused this portion of the chassis to operate as an I.F. amplifier and are free to engage with corresponding contacts upon the V.H.F. turret 300. The cam 368 which co-operates with cam follower 480 is shown in Fig. 40, which represents a section in the plane of back-plate 342 of U.H.F. turret 340, the cam 368 being attached to this back-plate. The cam 368 comprises a series of notches 371 and a further notch 495 in which, in the position shown in the Figure, the cam follower 480 is resting. This position corresponds with the V.H.F. position of the U.H.F. turret. As can be seen from the Figure, the contacts 428 are making engagement with the contacts on the V.H.F. turret 300. When, however, the U.H.F. turret is turned to an U.H.F. position, Fig. 41 (not shown), in which the cam follower 480 is engaged by one of the notches 371 the cam follower is raised, thereby causing a contact assembly 170 to rotate and contacts A<SP>1</SP>-M<SP>1</SP> mounted thereon to engage the portions 429 of the contacts 428 and lift them clear of the contacts upon the turret 300. The contacts A<SP>1</SP>-M<SP>1</SP> mounted upon the assembly 170 are connected to circuits such that the V.H.F. portion of the tuner assembly is caused to operate as an I.F. amplifier when the U.H.F. turret is in an U.H.F. position. In order that there may be one position of the U.H.F. turret wherein reception on V.H.F. and on U.H.F. are possible for different positions of the V.H.F. turret, the cam 368 is provided with a movable portion 369. A sector member 375 mounted on the shaft 310 of the V.H.F. turret supports the movable portion 369 for part of the rotation of the V.H.F. turret. However, when the U.H.F. turret is turned to the position under consideration and the V.H.F. turret is turned so that the sector 375 no longer supports the member 369 the member 369 is depressed by the cam follower 480 as is shown in Fig. 23, in which position the contacts 428 are free to engage the contacts on the V.H.F. turret 300. However, when the sector 375 is turned so as to support the portion 369, Fig. 24 (not shown), the cam follower 480 is lifted and the contacts A<SP>1</SP>-M<SP>1</SP> engage the contacts 428, the sector operating in this manner when U.H.F. channels 14 to 19 are being selected but allowing the contacts 428 to engage the turret 300 when the turret is turned to select any one of channels 10 to 13. Specification 781,064 is referred to.