Patent GB-626648-A (GB)
Title: Improvements in or relating to navigation aiding radio systems
IPC: G01S1/02
Filed: 1946-07-11
Abstract: 626,648. Radio navigation. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. July 11, 1946, No. 20802. Convention date, March 20, 1941. [Class 40 (vii)] A radio navigation system in which the location of an unknown position is determined from the times of propagation of pulses from said position to and from a pair of relay or reflector stations at known locations includes a main timing indicator and at least one fine reading indicator for indicating fractional portions of said propagation times. At the unknown position an oscillator 1 of say 500 c/sec. frequency controls the radiation of pulses by transmitter 65 and also feeds cascade multipliers 5 and 7 having outputs of 5 and 50 kc. respectively. Outputs from units 1, 5 and 7 are connected by switch sections 9 to ones of pairs of adjustable phase shifters 11, 13 ; 31, 33 ; 51 and 53 ; the pairs of which feed phase splitters 15, 35 and 55 producing circular timebase traces in cathode-ray tube indicators 19, 39 and 59. The transmitted signals may be alternately on different carriers which trigger different ones of the transponder stations or which are received alternately from different reflectors by synchronous switching of the receiver circuits or they may be of the same frequency in a system employing transponders radiating different return frequencies between which the receiver is switched. The received signals are used to produce radial deflections on the traces of the indicator tubes and there is sufficient break through of the transmitted pulses for these also to be visible. If it is desired to navigate from an unknown position to a given point distant " a " and " b " from the fixed stations the phase shifters 11, 31 and 51 are adjusted so that the transmitted pulse indications appear on the tubes retarded amounts corresponding to the distance " a " when the corresponding station is being interrogated and the phase shifters 13, 33 and 53 similarly adjusted according to " b " when the other station is interrogated. Switch 9 controlled by motor SM performs the required switching between the two interrogating and receiving conditions and at the same time switches to the correct phase shifters. If the craft carrying the apparatus is then manoeuvred so that the returned signals appear at the time base zero marks, using the vernier and fine vernier tubes 39 and 59 to achieve greater accuracy, it will then be at the required point. In the case of the vernier tubes where a deflection occurs only once every 10 or 100 revolutions of the time base trace the brilliancy of the indication may be increased by making the grid-radial deflection electrode potential of the cathode-ray tube greater at the instant of signal application, Fig. 3 (not shown). The indications on the tubes corresponding to the interrogation of the ground stations may be distinguished by introducing attenuation in one of the sets of phase shifters so that the set of signals corresponding to one of ground stations appears. on a time base trace of less radius than the other. Instead of an oscillator of the lowest frequency with multipliers a high-frequency oscillator and dividers may be used to control the decade indicating system.