GB607029A - Improvements in or relating to means for tuning wireless sets - Google Patents

Abstract

607,029. Tuning radio receivers. PHILIPS LAMPS, Ltd. June 4, 1946, No. 16942. Convention date, Oct. 16, 1939. [Class 40 (v)] In a wireless set having band spread-tuning on one or more bands, use is made of a variable auxiliary coil connected in series or in parallel with the main tuning coil, either continuously or only for band-spread tuning, the inductance of the auxiliary coil being varied during normal tuning simultaneously with the capacity of the main tuning condenser, while during band-spread tuning the main tuning condenser is cut out of circuit and is replaced by a fixed condenser defining the centre of a band in which band-spread tuning is effected by variation of the auxiliary coil. In Fig. 1, normal tuning is effected by a main tuning coil 1, together with a main tuning condenser 2 simultaneously variable with an auxiliary coil 3. For band-spread tuning switch 4 is moved to one of positions 6 ... 8 to connect an appropriate condenser 9 ... 11 in circuit tuning being effected by adjustment of the auxiliary coil 3. Coil 3 and condenser 2 are operated-by a single tuning knob. The auxiliary coil may be in series with the main coil, Fig. 2 (not shown). In Fig. 3, the auxiliary coil 13 is only connected in circuit when switch 4 is moved to one of the band-spread positions 6 ... 8. A similar arrangement for a parallel connected auxiliary coil is described in which two ganged switches are used for changing the connections, Fig. 4 (not shown). The variable inductance may be adjustable by moving a short-circuited turn, a metal plate or a high-frequency magnetic core by means of a spiral cam driven by a rotary shaft having the same angular movement as the shaft driving the main tuning condenser.