GB599647A - Improvements in and relating to press button tuned radio receivers - Google Patents

Abstract

599,647. Radio receiving sets. COLE, Ltd., E. K., and HUNT, H. Sept. 22, 1945, No. 24594. [Class 40 (v)] An intermediate frequency stage of a pushbutton radio receiver is adapted to be switched to give two degrees of selectivity, the selectivity switch being controlled by tuning switches, two switches corresponding to a station from which good quality reception is expected being provided, one giving low selectivity, whereas the other gives high selectivity. A coil 5, closely coupled to the primary 1 of a tuned I.F. transformer, is connected in series with the secondary coil 2. A trimmer condenser 6 is connected in series with the secondary tuning condenser 4. The shaft 7 of a push-button controlling the tuning of the receiver carries contact-makers co-operating with contacts A1 and A2 connected to one side of the trimmer 6, B1 and B2 connected to the junction of condensers 4 and 6, C connected to the junction of coils 2 and 5 and D connected to the other end of coil 5. For normal, low-fidelity reception, coil 5 and condenser 6 are short-circuited through contacts B2, C and A1, B1 respectively. When the push-button is operated, the contacts between A1, B1 and C, B2 are broken, but contact is made between A2 and D. In this position, coil 5 is in series with coil 2, and high fidelity reception is obtained. Trimmer. 6 serves to correct the frequency response curve when coil 5 is in circuit. The low-fidelity position may be automatically maintained, the high-fidelity circuit being used only when a push-button corresponding to a good quality station is operated. A station corresponding to a push-button which completes the highfidelity circuit may have an alternative pushbutton giving low-fidelity reproduction. Specifications 432,427, [Group XXXVI], and 469,380 are referred to.