GB535500A - Improvements in or relating to super-heterodyne wireless receivers - Google Patents

Abstract

535,500. Wireless receiving apparatus ; inductances. PHILIPS LAMPS, Ltd. March 20, 1940, No. 5230. Convention date, March 23, 1939. [Class 40 (v)] [Also in Group XXXV] To facilitate tracking in a superheterodyne receiver, a correcting member is arranged so as to be capable of being shifted in the field of at least part of the inductance present in the oscillator circuit, the displacement of the correcting member having a linear relation to the displacement of the tuning means, the member being so designed as to correct the divergency from the required frequency. Fig. 1 shows the oscillator circuit comprising a fixed inductance 1 which is tuned to the desired frequency by a condenser 3 in series with a padding condenser 4 and a variable inductance 5. The condenser 3 of the sliding electrode type is ganged to a similar condenser in the preselector circuit and also serves to move the correcting member to vary inductance 5 so as to correct for errors of tracking. A suitable form for the inductance is shown in Fig. 3. A coil 11 is wound on an insulating sleeve 10 inside which is an insulating rod 12 movable with the condenser electrode and which carries an iron core 13 and copper ring 14. When the iron core is within coil 11 the inductance is a maximum and acquires a minimum value when the ring 14 is within coil 11. In Fig. 6 the inductance comprises two coils 34, 35 in series with magnetic fields opposed, the inductance of which is varied by an iron core 33 shown in the position of minimum inductance. The coils may be of equal size. In a further modification, Fig. 9 (not shown), the inductance of a single coil is varied by the movement of an insulating rod on which are spaced two copper rings. To give a near approach to correct compensation the rings may be combined into a single copper body as at 52 Fig. 11 shown in the position of maximum inductance. In another modification, Fig. 13 (not shown), the correcting member comprises a pair of coils mounted on an insulating shaft and arranged one on each side of a fixed control coil. In a final modification, Fig. 14 (not shown), the correcting member comprises an iron core arranged between two copper rings mounted on and moved by a copper rod.