Patent GB-349977-A (GB)
Title: Improvements in or relating to radio beacons
IPC: G01S1/02
Filed: 1930-03-05
Abstract: 349,977. Directive wireless signalling. MARCONI'S WIRELESS TELEGRAPH CO., Ltd., Marconi House, Strand, London, FURNIVAL, J. M., Buna, Selcroft Road, Purley, and BUBB, W. F., Great Tey, Elmwood Road, Mitcham, both in Surrey. March 5, 1930, No. 7247. [Class 40 (v).] A radio beacon system comprises a pair of mutually perpendicular frames arranged to emit at regular intervals signals in two or more fixed directions so that both signals are received with equal strength in a predetermined direction, a rotating directional signal, a predetermined signal combination when the latter is passing through a known bearing, and a non-directional identification sign. Two crossed loops 1, 1a, comprising the aerial system are connected to goniometer coils 2 rotatable, through a magnetic clutch 13, by a worm wheel 9 revolved by a motor M<1>. The fixed goniometer coils 3, 3a are fed from an oscillator through lead K, magnetically operated switches 5, 5a, and amplifiers 4, 4a. The code wheels and contacts 6, 7, 8, continuously rotated by a motor M, and the code wheel 16, mounted on the goniometer shaft, produce the signals at the appropriate times, the selection being made by magnetically operated switches 19, 20, the former being controlled by a cam wheel 18 rotated at one-tenth of the speed of the goniometer shaft through gearing 14, 17, and the latter by a cam wheel 11 rotated at onetwentieth of the speed of the wheel 9 through gearing 9, 10. The cams 12, 15 control the current through the magnetic clutch 13. The system operates as follows:-A complete cycle of signals is radiated in twenty minutes, divided up into four periods of five minutes each, the wheel 9 being arranged to revolve once per minute and consequently the wheels 11, 12 once in twenty minutes. In the position shown and for the first five-minute period contact 11 is closed, energizing the switch 20, enabling the code-wheel 8 to key the switches 5, 5a with the general call sign which is radiated non-directionally from the complete aerial system. The goniometer coils 2 are stationary, contacts 12, 15 being open, and the clutch 13 de-energized. Contact 18 is open and switch 19 de-energized. After five minutes, contact 11 opens and de-energizes switch 20, resulting in the radiation from aerials 1, 1a of signals from code-wheels 7, 6 respectively, which consist of the letter A and the letter N respectively so timed as to give stationary equi-signal zones of radiation. After another five minutes contact 12 closes, energizes the clutch 13, and rotates the goniometer coils 2, so that the equi-signal zones are rotated through space at one revolution per minute. During this third fiveminute period, contact 18 is open and switch 19 de-energized. For the last five-minute period of the cycle contact 18 closes, switch 19 is energized, which de-energizes switch 5 and aerial 1, and keys switch 5a and hence aerial 1a with signals from the code wheel 16 which is arranged to produce a distinctive signal each time the rotating directional beam now emitted from aerial 1a passes through a predetermined bearing. At the end of this period and the twenty-minute cycle, contacts 12, 15 open, the clutch 13 is de-energized, contact 18 is opened, contact 11 is closed, and a new cycle commences. The non-directional signal may be transmitted by arranging the relays to connect the loops together and to earth through a suitable coil.