GB130107A - Improvements in Apparatus for Eliminating Interference in Wireless Telegraphy. - Google Patents

Abstract

130,107. Marconi's Wireless Telegraph Co., and Richmond, H. April 25, 1918. Wireless telegraphy.-Wireless receiving-apparatus, adapted to prevent interference bv signals from undesired stations, comprises a pair of directive aerials ABCD, EFGH, Fig. 2, including inductances I, J and K, L respectively, which are adjustably coupled to coils P, P<1> connected in series or in parallel to the receiving-circuit. The station with which it is desired to communicate lies in the plane of one of the aerials, say ABCD, and signals from this station are transferred to the receiving-circuit by the coupling of the coils I, J to the coil P, while the signals produce no effect in the other aerial. Signals from an undesired station affect both aerials, and, by adjusting the coupling of the coils P, P<1> to the aerials, the undesired signals may be neutralized in the receiving-circuit. During normal reception, it is preferred to have a loose coupling of the coil P to the receiving-aerial ABCD, the other aerial being tightly coupled to the coil P<1>. The couplings may be so arranged that, when one is a maximum, the other is a minimum, and coupling between the inductances I, J and K, L is avoided. The aerials are tuned to the same frequency. In a modification, Fig. 1, a single coil O is placed in the field of the inductance coils I - - L, and the distance of these from the single coil is adjustable so as to produce an unsymmetrical field.