Patent GB-328315-A (GB)
Title: Improvements in or relating to direction-or position finding and recording apparatus
IPC: G01S1/02
Filed: 1928-12-28
Abstract: 328,315. Wheatley, C. H. P. Dec. 28, 1928. Addition to 300,697. Bearings and distances, determining; directive signalling.-Relates to automatic or semi-automatic wireless direction-finding apparatus. The varying field-strength of a rotating beam of energy, or the varying pick-up of a. rotating frame aerial used for reception, is utilized to measure angular intervals by means of moving members which thereby indicate the geographical position of the receiver. The apparatus shown in Fig. 1 is controlled by the energy received from a rotating loop transmitter modulated by a twin-note which is interrupted to give a characteristic signal along the North-South and East-West lines. The receiving operator situated along the line A, Fig. 9, on first hearing the characteristic note pushes a plunger 29 to the limit of its stroke, thereby engaging a clutch 50 to a rotating shaft 13 and coming signal reaches it point of minimum to start moving upwards. Next, when the incoming signal reaches its point of minimum strength, corresponding to the line WE, Fig. 9, the operator depresses a lever 26 out of the path of a stop 27 to allow a, disc 24 to rotate through an arc determined by a second stop 28. This motion causes a second clutch 49 (previously free) to engage the shaft 13 and start the upward movement of a second rack 40 away from its stop 18. Simultaneously the clutch 50 is disengaged and the rack 20 is held stationary after having traversed a distance equivalent to the angle G, Fig. 9. The movement of the rack 40 continues until the second point of minimum signal strength is reached, so that it traverses a distance corresponding to the angle B, Fig. 9. At this point, the operator again moves the lever 26 to allow the disc 24 freedom to rotate into contact with the first stop 27. Both racks 20 and 40 are now held stationary, and a link member 32 indicates the geographical position of the receiver on a suitably calibrated scale 30. In an alternative arrangement, shown in Figs. 4, 10 and 12, the directional rise and fall in signal strength and the twin-note modulation signal are used in combination to set the indicating means to the required position. The modulation note operates two vibrating-reed contacts 54, 55 tuned to the respective frequencies. When the operator hears the characteristic signal in the telephone earpiece 63 (which is connected directly to the amplifier 60) he pushes the plunger 29 and, causes the rack 40 to start moving over the full-line angle G, Fig. 12. When the energy falls off to a point insufficient to maintain the vibrating reed in contact, the operator hears this condition in the earpiece 62 (which is in the common output of the series-connected valves 52, 53) and depresses the lever 26, and so brings into operation epicyclic gearing, which causes both the racks 40 and 20 to move at half speed. At a. point of equal arc on the other side of minimum signal strength. the rack 40 is held stationary so as to bisect the dotted-line angle G. The rack 20 is left to move at full speed until a corresponding point (short of the point of minimum signal strength) is reached, whereupon it is rotated at half speed over the portion shown in dotted lines, the result being that the dotted-line arcs are in effect bisected. At the end of the cycle the required position is shown by the indicator 31 on the calibrated scale 30. In a modified arrangement, the vibrating-reed relay of Fig. 4 is utilized to secure an entirely automatic record of position by utilizing a rotating beam of energy oscillating about the point N, Fig. 15, first clockwise and then counterclockwise. The operation depends upon a bisection of the angle between the point at which the leading edge of the full-line polar diagram when rotating clockwise becomes effective, and the point at which the corresponding leading-edge of the dotted-line field becomes operative in the backward or counterclockwise ewing of the rotating beam. A further modification is described in which the indicating link work is energized from the lubricating system of the internal-combustion engine driving an aeroplane or other moving craft on which the wireless receiving apparatus is being carried.