Patent GB-405322-A (GB)
Title: Improvements in directional radio receiving apparatus
IPC: G01S19/42
Filed: 1932-08-03
Abstract: 405,322. Directive wireless signalling ; valve circuits. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Taylor, L. A. ; 144, Country Club Drive, Schenectady, New York, U.S.A.) Aug. 3, 1932, No. 21809. Convention date, Aug. 3, 1931. [Class 40 (v).] Means are provided for maintaining constant the sensitivity of response of a direction indicating device at different distances from the source of the received waves. The receiving system comprises means controlled by the currents from a directional aerial for supplying to the indicator a plurality of currents having a phase relation dependent on the direction of the aerial, a substantially constant intensity relation being maintained between said currents. In one embodiment, audio-frequency currents, e.g. of one thousand cycles are generated by a valve 3, Fig. 1, by back coupling through the windings 13, 14 of transformer 15, and are supplied from the winding 24 of transformer 15 through transformer 23 in parallel to the grids of valves 10, 11 which are supplied in push-pull with currents from the wireless receiver 3-8. To the input of valve 3 is coupled the directional loop aerial 1 and the signals after amplification and modulation by the audio frequency in valve 3 are applied together with signals from the non-directional aerial 2, to the H.F. amplifier 4, detector 5, L.F. amplifier 7 and push-pull valves. The phase of these currents relative to those supplied by transformer 23 is shown to depend on the direction of the aerial 1 relative to the incoming waves and the current indicator 12 connected in push-pull to the output of valves 10, 11 moves to the left or right depending on the orientation of the aerial 1 and by an amount depending on the phase difference between the currents supplied to these valves. In order that the same deflection shall correspond to a constant deviation of the aerial 1 from the direction of the transmitter at any distance therefrom, automatic gain regulating means are incorporated in the amplifier and comprise a resistance 30 in the anode circuit of the detector 5, the potential drop in which is used to bias the control grid of the H.F. amplifier 4. The time constant of the gain control is adjusted by the choice of condensers 34 and 16<1> in parallel with the resistance 30 and the H.T. source 25 respectively so that it does not respond to the rapid variations in intensity of the signals due to the low-frequency modulation. In a modification (Fig. 2, not shown) the winding 14 of the transformer 15 is omitted and locally generated audio-frequency currents are supplied to the winding 24 and the transformer 23. In another embodiment, Fig. 5, audio-frequency currents from a generator 35 are applied to the screening grid of valve 3 from the potentiometer 39 connected across the secondary winding 38<1> of transformer 36. The output from the detector 5 passes to winding 40 of a direction-indicating phase meter 41, the other winding 42 being supplied with currents from the source 35. The directive aerial 1 is used also to give the non-directional signals, applied to the valve 4, in known manner. A separate detector 5<1> is connected in parallel with the detector 5 to provide the gain control. It comprises a screen grid valve with the resistance 30 in its anode circuit feeding grid biassing potential through the time-control circuit 43-47 to the valve 4, and its screening grid is fed through a potentiometer 38 across a winding 37 of the transformer 36 with potentials which neutralize any tendency of the gain regulator to operate at the frequency of the source 35.