GB269686A - Improvements in tuning devices for radio receivers - Google Patents

Abstract

269,686. British Thomson-Houston Co., Ltd., and Kinman, T. H. Jan. 26, 1926. Inductances; wireless tuning-apparatus, adjustment devices for.-A tuning-device for radio receivers comprises a main tapped inductance, the sections not in use being short-circuited and variably coupled with a reaction coil having a fixed number of turns, the coupling between the active turns of the inductance and the reaction coil being insufficient to produce self-oscillation when passing from one wavelength to another. As shown, the main inductance comprises sections La - - Ld connected to contact plates Ca - - Cd, a reaction coil R being slidably mounted on an operating spindle S1. A contact c mounted on a spindle S2 is geared with the spindle S1 and the arrangement is such that before contact is made with the contact plate Cb the reaction coil is completely encircled by the inductance section Lb. The last inductance section Ld is permanently short-circuited and may be replaced by a non- magnetic plate or sleeve. The usual tuning condenser in parallel with the main inductance may have its rotor plates mechanically connected with the reaction coil for simultaneous adjustment. A number of such tuning devices may be employed in series in multi-valve circuits and they may function as coupling, reaction or neutralizing coils. A co-operating pointer and scale I. S indicate the amount of inductance in circuit.