Patent GB-571836-A (GB)
Title: Improvements in or relating to variable permeability tuning arrangements for radio or like apparatus with band-spread tuning
IPC: H03J3/10
Filed: 1943-10-25
Abstract: 571,836. Wireless receiving apparatus. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Oct. 25, 1943, No. 17503. Convention date, Oct. 24, 1942. [Class 40 (v)] . [Also in Group XXXVI] A variable permeability tuning arrangement for a multi-band short-wave radio receiver comprises a tuning core or cores adjustable to predetermined positions corresponding respectively to frequencies within the several bands, and means including an auxiliary continuouslyadjustable core operable to adjust tuning on .either side of said frequencies for effecting bandspread tuning within each of said bands. Fig. 1 shows the input stages of a superheterodyne receiver comprising an aerial A, RF stage RF, oscillator-mixer O, and intermediate frequency transformer IF. For the broadcast band, tuning is effected by simultaneous adjustment of cores 1<1>, 2<1>, 3<1> of coils 1, 2, 3 serving to tune the aerial, RF stage, and oscillator respectively. For the short waves the circuit comprises a band pass filter having coils 4, 5, an RF circuit tuned by coil 6, and an oscillator circuit tuned by coil 7, and auxiliary coil 8. In short-wave tuning the cores 4<1>, 5<1>, 61 and 71 are simultaneously moved by a control U<1> to select the midfrequency of the desired band, and then bandspread tuning throughout the selected band is effected by moving auxiliary core 81 by a control U which also serves for moving the cores 1<1>, 21, 3<1> of the broadcast coils 1, 2, 3. Changeover switches S1 ... S5 are provided for changing from the broadcast to the short-wave bands. Fig. 2 shows a constructional form of adjusting device, in which the short-wave cores 41, 5<1>, 6<1> and 7<1> are adjustably mounted on a carrier C1 slidable on rods R, while the auxiliary core 8<1> is mounted on a carrier C2 which also carries the broadcast cores 1<1>, 2<1>, 3<1>. Carrier C1 is biassed to the right by a spring 32 and the rest position is determined by the engagement of an extension E of the carrier with one of a number of adjustable screws 18 ... 21 carried in a turret rotatable by a spindle S and knob K1. The turret comprises discs D1, D2 through which the screws are threaded, the discs being biassed for rotation in opposite directions by means of a spring 22 so as to lock the screws in their adjusted positions. When knob KI is turned for selecting a short-wave band, switches S1-S5 are operated to the desired position and a commutator Co causes energization of an electromagnet RS to move the carrier C1 to the left. When the desired position is selected, contacts B fall on an insulating portion of the commutator to de-energize the magnet RS and allow'the carrier to return to the' left, the position depending on the engagement of extension E with a selected one of the screws 18 ... 21. Band-spread tuning over the selected band is then effected by knob K2 causing movement of carrier C2 and hence of the auxiliary core 8<1>. For broadcast tuning, switches S1 ... S5 are set to the broadcast position and knob K2 is used to adjust cores 1<1>, 2<1>, 3<1> through the medium of carrier C2. In modifications, Figs. 3 and 4 (not shown), the short-wave cores are divided into groups mounted on two or more carriers controlled by two or more sets of screws on the turret so as to facilitate tracking of the various circuits.