GB435255A - Improvements in tuners for high frequency currents - Google Patents

Abstract

435,255. Wireless receiving-apparatus. OLIVER PELL CONTROL, Ltd., Cambridge Place, Burrage Road, Woolwich, London, OLIVER, C., 3, Shepherd's Green, Chislehurst, Kent, and MOODY, G. H., 6, Harland Road, Lee, London. Feb. 12, 1934, No. 4628. [Class 40 (v)] [See also Group XXXVI] A permeability tuning arrangement for two or more wave ranges comprises an inductance coil having two or more concentric windings connected to the wave - change switch so that on short wave working, the windings not in use are disconnected without being short-circuited, a common magnetic core being employed for both wave ranges. Two or more condensers are also associated with the wave-change switch and auxiliary tracking condensers may be employed The coils L1, L2, on a former 1 are aligned with the movable core 2 which may include a cupshaped part 3, and are located in a screen 4. A coil L3 on a former 6 may be used in conjunction with the coils L1, L2 and may provide reaction or other coupling, or it may replace the coil L2. Thin insulation 7 of ebonite or of material known under the Registered Trade Mark "Trolitul," of a thickness between 4 and 10 mils, may be used. In one switching arrangement Fig. 3, condenser C2 is connected across the condenser C<1>, switches S, S1 being mechanically coupled so that when the winding L2 is disconnected, the condenser C2 is also open-circuited. Alternatively the condenser C2 may be short-circuited. A further small condenser controlled by the core movement may be employed to compensate for irregularities in the inductance variation. Specification 429,826, [Group XXXVI], is referred to.