GB281776A - Improvements in or relating to wireless or like amplifying instruments - Google Patents

Abstract

281,776. Brown, W. J., and Metropolitan-Vickers Electrical Co., Ltd. Sept. 10, 1926. Thermionic valve circuits.-In a wireless receiver in which the source 10 of high tension comprises the D.C. mains or a source of rectified A.C., hum is eliminated by means of two different filter circuits applied respectively to the power valve 8 and the preceding amplifier and detector valves 2, 4, 6, which are all provided with resistance-couplings as indicated at 3, 5, 7. The filter for the power valve comprises a, coil 13 of great current capacity but less inductance than the coil 12 associated with the earlier valves; the coil 13 consists of thick, the coil 12 of thin wire, and each is wound to the same bulk on one of the halves of the laminated core shown in Fig. 3. This arrangement makes use of the fact that the power valve is less sensitive than the earlier valves to humming voltage components, owing to its lower amplification factor. The total bulk of the coils is less than the bulk of a single coil suitable for all the valves. Each coil is shunted by a condenser 14, 16, and a common condenser 18 may be added; the end 20 of the coil 12 may be connected to the source 10 either directly or through a potentiometer 19 as shown. The coil 12 and condenser 14 may be replaced by a group of series coils and shunt condensers. The Specification mentions suitable dimensions for the parts of the apparatus. Reference has been directed by the Comptroller to Specification 275,624.