Patent GB-604132-A (GB)
Title: Improvements in or relating to equi-signal radio beacon systems
IPC: G01S1/02
Filed: 1943-03-01
Abstract: 604,132. Directive wireless systems. O'BRIEN, W. J. March 1, 1943, No. 2061/45. Convention date, March 2, 1942. Divided out of 583,361. [Class 40 (vii)] In an equi-signal radio-beacon system, the two signals having different directional characteristics are radiated respectively during the positive and negative half-cycles of a modulation by a complex wave form having positive and negative peaks at unequal intervals, for example the wave form 52, Fig. 2, or 52a, Fig. 7, formed by the combination of a fundamental 50 or 50a with an harmonic 51 or 51a. The transmitter system shown in Fig. 1 comprises two antennµ A, B spaced two wave lengths apart and a central antenna C as described in Specification 588,024. The antennµ A, B are coupled through loading devices 30, impedance matching transformers 31, and coaxial cables 33 to a source of radio frequency 32. Antenna C is similarly coupled to a power amplifier 34. Radio frequency is supplied from source 32 through a transformer 36 to a modulator 35 coupled by a transformer 48 to the power amplifier 34. The complex wave form is fed to the modulator 35 through a transformer 49. A receiver system giving indications on a cathode-ray tube is shown in Fig. 8. An antenna 65 is connected to a radio receiver 64, the output of which is fed to a rectifier 68. The rectified output on a resistance condenser combination 70, 72 is normally passed by a condenser 73 to an amplifier 75 and thence to another amplifier 80 connected to the vertical deflection plates 87 of a cathode-ray tube, and to a saw-tooth generator 90 producing a time base by its periodic action on the horizontal deflection plates 89 of the cathode-ray tube. The signal received on the equi-signal course appears on the screen of the cathode-ray tube as shown in Fig. 12. On one side of the course, the peaks of the signal change in the manner indicated in Fig. 10 ; and on the other side of the course, opposite changes occur as shown in Fig. 14. Moreover, the extent of the changes varies with the extent of deviations from the course. If statics and other disturbances interfere with the signals, better results may be obtained by causing the output of the rectifier 68 to be modulated by an oscillator 103, and feeding this modulated output to the amplifier 80 through an amplifier 105 having a sharply tuned coupling transformer 107. A receiver system giving indications by the deflections of a pointer is shown in Fig. 9 for receiving signals of the kind indicated in Fig. 7. The signals received by a radio receiver 109 from an antenna 110 are rectified in a rectifier 112. The rectified signal is fed to the grids of two tubes 116, 117 in parallel. The output of these tubes is fed through two tuned transformers having their secondaries in series to an amplifying tube 123. One transformer 118 is tuned to the second harmonic of the modulating frequency, and the other transformer 119 to the fundamental, one or both being however slightly detuned to produce a phase difference between the two channels. The output of the tube 123 is fed through a tapped transformer 126 to a pair of amplifier tubes 128, 129, between the anodes of which a low resistance galvanometer 134 is connected.