GB146997A - A method of and apparatus for receiving radio signals - Google Patents

Abstract

146,997. Hogan, J. L. Nov. 27, 1916, [Convention date]. Directive wireless signalling.-Apparatus fur reducing interference from atmospherics comprises two receiving-aerials, one or both of which are of the directional type, connected differentially to the receiving-instrument, one of the aerials being so arranged that it gives minimum response to signals from the desired direction, whilst both aerials are affected equally by atmospherics which are consequently baianced out in the receiving-instrument. Fig. 1 shows one arrangement for heterodyne reception, Fig. 8 shows another arrangement without heterodyne, and Fig. 3 shows a modification employing an electrostatic telephone receiver. As shown in Fig. 1, a directive aerial 31 is set up to give maximum response to the desired signals, and an auxiliary directive aerial 32 is arranged to give minimum response to such signals. Both are affected substantially equally by atmospherics. The secondary circuits include detectors 8, 17, and heterodyne sources 25, 26 have their circuits inductively related to the secondary circuits, giving beat tones through the receiver 3. This receiver is oppositely connected to the two circuits so that static signals which are of substantially equal value are balanced out. The desired signals, however, produce little effect on the aerial 32, and are consequently heard in the receiver. A single heterodyne source may replace the two sources 25, 26. In the modification shown in Fig. 8, loop aerials 35, 36 are employed, one of which 36 is placed so as to be irresponsive to signals from the desired direction S. The detector circuits are connected respectively to oppositely-wound transformer coils 10, 19, the third coil 11 being connected to the telephone 3. Separate telephones may be placed in circuit with the coils 10, 11 to enable independent tuning and other adjustments to be made, and when the effects of atmospherics in the two telephones is substantially identical, both are cut out by short-circuiting switches. The circuit of the telephone 3 may include a condenser for tuning to group frequency. The signal-receiving aerial 31 or 35 may be a vertica'i non-directional aerial. The auxiliary aerial 32 or 36 may also be a vertical aerial screened from the desired signals by a number of vertical grounded wires placed symmetrically round it. The crystal detector may be replaced by a thermal or thermionic detector; or an electrostatic telephone may be employed as shown in Fig. 3. In this arrangement, the telephone 29 is placed in a circuit, including coils 7, 16 coupled to the aerials 31, 32 and a coil coupled to a heterodyne circuit 30. This arrangement depends for its action partly on the difference in signal strength received upon the two aerials, and partly upon the phase difference of the signal waves.