Patent GB-641809-A (GB)
Title: Radio range beacon
IPC: G01S1/02
Filed: 1947-07-18
Abstract: 641,809. Radio navigation. STANDARD TELEPHONES & CABLES, Ltd. July 18, 1947, No. 19276. Convention date, Feb. 5, 1946. [Class 40 (vii)] In a radio beacon system the beacon cyclically and successively transmits signals in a plurality of differently - directed overlapping radiation patterns, and a receiver synchronously selects the energy defining the different patterns to indicate the azimuth position of the receiver by comparison of the magnitude of the received energies. The system which is omnidirectional comprises beacons providing coarse and fine indications and operates on long waves with narrow band modulation. Transmitter. The coarse beacon comprises three aerials 1, 2, 3, Fig. 2, spaced apart 0.4# and energized cyclically and cophasally in pairs to produce radiation patterns 19, 20 and 21. Intermediate each cycle a single aerial radiates a synchronizing signal omnidirectionally. Fig. 3 represents the cycle of signals which are of pulse form, and in which 14 is the synchronizing signal and 15, 16 and 17 the signals due to the three patterns. The fine beacon employs a second triangular array of aerials (not shown), which are spaced apart a plurality of wavelengths so as to produce multi-lobe patterns and are arranged on the same centre as triangle 1, 2, 3. These radiators are similarly energized cyclically in pairs but for periods during which the pair are first energized with 180 degrees phase relationship, then - 60 degrees and then + 60 degrees, so producing three different patterns. Intermediate each such period a characteristic synchronizing signal is transmitted omnidirectionally by a single aerial. Fig. 5 represents the cycle of signals where single-pulse signal 50 is the synchronizing signal for the first pair of indicators and 51, 52, 53 the signals corresponding to the three phases of radiation. Double-pulse signal 54, 55 marks the three signals 56, 57, 58 for the second pair of radiators, and triple-pulse signal 60, 61, 62 marks the three signals 63, 64, 65 for the third pair of radiators. Receiver. A receiver 22, 23, 24, Fig. 4, feeds a main detector 36 through a normally closed gate 26 and also an auxiliary detector 27. For operation with the coarse beacon, switch 28 applies the received signals to circuit 29 which selects the synchronizing pulse 14 to apply to the deblocker circuit 31 which in turn opens gate 26 to allow signals 15, 16, 17 to pass to the main detector 36. The synchronizing pulse also operates through circuits 33, 34 a distributor 37 whereby pulses 15, 16 and 17 are properly distributed to the coils 41, 42, 43 of a ratiometer indicator 35. Associated with each coil is a storage condenser 44-46. Pointer 47 takes up a position dependent upon the energy level in each coil and indicates the receiver azimuth. For operation with the fine beacon, switch 28 applies the received signals to circuit 49 which may be set to one of three positions 66, 67, 68, dependent upon the sector in which the receiver is located, so as to select synchronizing pulse signal 50, 54, 55 ; or 60, 61, 62 and allow the receiver to operate with the appropriate pair of radiators. Deblocker circuit 70 and circuits 71 and 34 operate as described for the coarse beacon to allow the selected group of pulses, say 56, 57, 58, to be properly distributed to the indicator coils. However, only two of the radiated patterns are used for comparison and switch 72-75 selectively isolates one of the ratiometer coils. A calibrated chart may indicate to the operator the best patterns to employ for any position of the receiver. Indicator 35 carries a scale for use with the coarse beacon, and a further scale calibrated in segments and sectors for use with the fine beacon. The coarse beacon provides an accuracy of 1 or 2 degrees and has an ambiguity of 180 degrees. The fine beacon provides an accuracy of <SP>1</SP>/ 10 th to <SP>1</SP>/ 20 th degree. Specification 631,172 is referred to.