GB594532A - Improvement in omnidirectional radio navigation-aiding systems - Google Patents

Abstract

594,532. Directive wireless signalling. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. Aug. 8, 1944, No. 15097. Convention date. Sept. 30, 1942. [Class 40 (v)] In a navigational beacon in which a field pattern with a rotating directional component is radiated, a reference phase is provided by an omnidirectionally radiated carrier of the' same frequency which is modulated at a frequency which is an integral multiple and at a frequency which is an integral submultiple of the frequency of rotation of the directional pattern. At the transmitter, Fig. 1, a 60 c.p.s. voltage obtained from the 720 c.p.s. oscillator 13 by frequency divider 15 is fed to balanced modulator 1 and also through 90 degrees phaseshifter 17 to the balanced modulator 3. The radio frequency input to the modulators is provided by oscillator 5 and amplifier 7 and the modulator outputs are fed to the aerials N, S, E and W to produce a radiation pattern rotating at 60 c.p.s. Radio frequency from power amplifier 9 is radiated omnidirectionally from aerial 11 and modifies the radiation from aerials N, S, E and W to produce a rotating cardioid pattern. The output from amplifier 9 is also modulated by modulator 23 with 20 c.p.s. obtained from frequency divider 19 and 720 c.p.s. from oscillator 13 combined with the 20 c.p.s. in circuit 21. The output from receiver 25, Fig. 2, is fed to filters 29, 31 and 33 which select respectively the 20 c.p.s. and 720 c.p.s. signals and also the 60 c.p.s. modulation produced by the rotating pattern. The 720 c.p.s.component is fed directly to one deflection circuit of the cathode-ray oscillograph 35 and through the 90 degrees phase-shifter 37 to the other deflection circuit to produce the circular trace 49, while the 20 c.p.s. component after conversion to 60 c.p.s. in the multiplier 34 is fed to the 90 degrees phase-shifter 41 and cathode-ray tube 39 to produce the circular trace 51. The 60 c.p.s. modulation from filter 33 is fed to an impulse shaper 43 producing one sharp pulse corresponding to the peak of the modulation cycle which is fed to radial deflection circuits of tubes 35 and 39 to produce the deflections 45, 47. The face of tube 39 may be calibrated in bearings in coarse steps of 30 degrees, while the face of tube 35, the trace on which occurs twelve times during one rotation of the directional pattern, is calibrated over a range of 30 degrees to provide fine bearing indications.