Patent GB-767489-A (GB)
Title: Improvements in or relating to radar training apparatus
Inventor: SWIFT JAMES WALTER
IPC: G01S7/40
Filed: 1954-07-16
Abstract: 767,489. Trainers for radio-navigation. COMMUNICATIONS PATENTS. Ltd. June 29, 1955 [July 16, 1954], No. 20748/54. Class 40(7) A device for simulating a radar display for the purpose of training operators includes a display cathode ray tube and means for applying to it combinations of varying and steady deflection potentials to scan a desired area on the tube face and so indicate the position of an extensive obiect. The embodiment described with reference to the Figures discloses a device of this kind incorporating additional means for simulating on the same display a representation of a group of craft which follow substantially the same course at substantially the same speed. Apparatus for performing the latter function forms the subject matter of Specification 767,490. In this embodiment apparatus for indicating a coast line by means of four extensive markings and also a convoy of four ships is described; it being assumed that the simulated radar is itself on board a further ship. Fig. 1 shows circuits for generating the N.S. deflection voltages, the E.W. circuits being substantially the same. The N.S. circuits themselves consist of two identical circuits, the controls of which are ganged but the source potentials of which are of opposite polarity, so only that circuit whose output is applied to deflection plate 28 of the cathode ray tube indicator will be described. In this a battery 11 supplies a potentiometer 10 positioned or driven (as by an integrating motor unit) in accordance with the supposed position of the radar carrying craft and a corresponding potential is fed to contact a of switch 12 and to plate 28 itself. A further potentiometer 13 across battery 11 is set according to a chosen position on the proposed coast line indication and its slider connected through resistor 14, across which an adjustable A.C. modulation can be impressed as indicated, to contact b of switch 12. Further switch contacts c, d and e are connected to separate potentiometers 16, 17 and 18 in parallel across source 19, and equal resistors 20 and 21 across that source are connected to contact b. Potentiometers 16, 17, arid 18 can thus be adjusted to extend the coast line indication as required. Battery 11 also supplies potentiometer 22 set in accordance with the North-South position of the leading craft of the group to be indicated. This potentiometer is connected to contact g of the switch 12 and to the centre contact 23a on a slab-type sine cosine potentiometer 24. A further battery 25 is connected across the potentiometer 24 by means of slip rings 27 (see Fig. 2) and adjustable contacts 23b, 23c and 23d, positioned with respect to the central contact in accordance with the positions of the other ships in the group with respect to the leader, are coupled to switch contacts f, h, j. The potentiometer 24 is adjusted about the central contact in accordance with the heading of the group of ships and resolves the distances between the leader and the other ships to obtain the North-South components, voltages proportional to which are added to the potential tapped off from potentiometer 22. If it is necessary to simulate relative movement between the ships of the group further potentiometers will be necessary, connected in parallel with potentiometer 22. The potentials on the contacts of switch 12 thus represent the North-South positions of the radar itself, four parts of a coastline and a group of 4 ships. The wiper of the rotary switch is earthed and thus, as it rotates, there is fed to deflection electrode 28 zero potential corresponding to the radar position and then four A.C. modulated potentials to produce relatively correctly placed coastline indications and finally four voltages corresponding to. the positions of the ships. The similar circuits shown connected to plate 28 with controls ganged to those described complete the means for providing the N.S. deflection potentials. Circuits for the E.W. potentials are similar except that the frequency of the alternating source is made 2 Kc/sec. instead of 50 c/sec. in the N.S. circuits. This means that the extensive areas of the parts of the coast line are scanned out as solid areas, the illumination of which may be made more even by making the waveform of at least the lower frequency saw-tooth in shape. Brightening pulses may be generated in synchronism with the positioning of the switch 12 which may be moved on step by step by means of a pulse fed device or motor driven Geneva mechanism. The voltage across the slab potentiometers may be varied to spread out or close up the indication of the group of ships and switches may also be provided to suppress individual ones of the ship indications. A different top-plate 30 (Fig. 2) with a modified arrangement of contacts may be substituted to change the positional relationships of the ships. By suitable choice of scanned areas the coastline may be made continuous and more contacts on the switch may be made available so that a more complex pattern can be produced. The shape of the individual areas can be varied, for example, by modulating the 2 Kc/sec. alternating current at a low frequency.