Patent GB-805756-A (GB)
Title: Improvements in or relating to radar systems
Inventor: WATT JAMES
IPC: G01S7/04
Filed: 1955-05-24
Abstract: 805,756. Recording-apparatus. MARCONI'S WIRELESS TELEGRAPH CO. Ltd. May 14, 1956 [May 24, 1955], No. 14941/55. Class 106 (4). [Also in Groups XX and XL (c)] In a ship-borne radar comprising a rotating directional aerial 6 (see Group XL (c)), the echo signals are applied to a selecting circuit which produces recurrent electrical recording pulses whose timing is proportional to the range of a reflecting object and the pulses are applied to a stylus which is displaced cyclically along a radial arm which is rotated over an electrochemical recording paper such that the mark produced by each recording pulse indicates the range and bearing of the reflecting object; the recorder and record paper may also be relatively displaced in accordance with the movement of the ship. The radial displacement recurrence period of the stylus may be less than or greater than the rotation period of the stylus arm. As described, each recording pulse comprises a short burst of 100 Kc/s. sine waves. In Fig. 1 three stylii (one only shown at 20) are equally spaced on an endless metal belt 19 driven by a constant speed motor 21 and supported by a radial arm 14 attached to a shaft 13 driven by a gearing 16 coupled to an aerial magslip 9 and compass repeater 15 such that the angular position of the arm 14 corresponds to the instantaneous true bearing of the rotating aerial 6 and such that each stylus comes into contact with the electrochemical recording paper 22 as the one in front leaves the paper. The paper 22 may be changed by turning a handle 23 which may be replaced by a drive from the ship's log. In another embodiment, Fig. 2, the recorder arm and aerial 6 are rotated synchronously at a high speed, e.g. 100 r.p.m., and the motor 21 produces a radial traverse of a stylus in one minute so that each stylus describes a spiral path. The recorder assembly is mounted by a pillar 69 on a triangular platform 70 having a circular aperture 71 through which the shaft 13 passes. The platform has three castor wheels 72, 73, 74 which rest on the record paper 22, the wheels being oriented in accordance with the ships heading by means of a chain 75 driven by a compass repeater 30 and the wheel 72 being driven by a ship's log repeater motor 81 so that the platform 70 moves in accordance with the movement of the ship. The ship's track X is recorded by an additional intermittently energized stylus (not shown) located under the shaft 13. In a modification, Fig. 3 (not shown), the radial arm 14 is rotated at a higher speed than the aerial and the recording signals are applied to the stylus belt 19 whenever the alignment of the arm 14 and the aerial correspond by means of a rotary switch controlled by the gearing 16 and the shaft 13. In another form of recorder, Fig. 4 and Fig. 4a (not shown), a peripherally toothed annular disc 100 is rotated synchronously with the aerial by a magslip 9 and a radial arm carrying a stylus 102 is displaced radially inwards in discrete steps by means of a toothed rack 103 and pinion 114 driven by a ratchet wheel 105 which is rotated one tooth when it comes into contact with a fixed striker 106. When the stylus reaches its final position the pinion 114 is released by a cam 112 and the stylus arm is returned to its initial position by a helical spring and the cycle repeats. The ship's heading is indicated by a lamp 116 mounted on the disc 100 diametrically opposite the stylus and energized when the aerial is directed astern. The record paper 22 is driven by a step-by-step motor 118 through a two-speed gear-box 119. In all the embodiments the time required to build up a picture with a given range discrimination may be reduced by replacing each stylus by two mutually - insulated radially - displaced stylii coupled to respective signal selecting means controlled by respective gating or control signals. As applied to the recorder shown in Fig. 4, the radial displacement between the two stylii may be equivalent to three circular lines such that the first and fourth lines are traced in the first revolution of the disc 100, the third and sixth are traced in the second revolution, the fifth and eighth in the third revolution &c.