GB544893A - Interference eliminator for wireless receivers - Google Patents

Abstract

544,893. Protective arrangements. BOLE, F. E., EDWARDS, C. M., and MACLAUGHLIN, J. B. Oct. 30, 1940, No. 15883. [Class 38 (iv)] [Also in Group XL)] In order to eliminate undesired frequencies and electrical disturbances in a receiving set, a variable filter is connected across the power line and is adjusted so as to absorb or eliminate interference on the line. The power transformer D of a receiver E is supplied from A.C. mains 10, 11 the latter of which is earthed. Between the mains 10, 11 are connected a pair of broad band filters H, I, each consisting of an inductance, resistance condenser connected in series. The filter H comprises an inductance 18, connected to the main 11, a resistance 20, and a condenser 21 connected through a switch 23 to the opposite main 10. The filter I comprises an inductance 14 connected to the main 10, a resistance 15, and a condenser 17 connected to the opposite main 11 through a switch 22, so that the filters H, I are oppositely connected across the mains. The junction of the resistance and condenser in each filter is connected through a switch 25, 26, condenser 32 and switch 31 to earth 24. The filter elements are enclosed in a copper screen J. Various circuit arrangements of the filter elements may be made by means of the switches 22, 23, 25, 26, 31, which may be combined to form a multiple rotary switch with a single control giving different circuit combinations in different positions. The apparatus may be combined with the means associated with the antenna for reducing interference from that source, which forms the subject-matter of Specification 544,933.