Patent GB-1307623-A (GB)
Title: Loran trainer
IPC: G09B9/26
Filed: 1970-08-10
Abstract: 1307623 Radio navigation simulators SINGER CO 10 Aug 1970 [20 Aug 1969] 38412/70 Heading H4D A radio navigation training system comprises a source of navigational information in the form of digital numbers, at least one radio navigation receiver, and means interconnecting said source and said receiver for transforming the digital numbers received from said source into signals which simulate radio navigation transmissions, and means for applying said signals to said receiver. The interconnection means comprises at least a counter and a first register, at least one input to each of said counter and register being connected to an output of said source, so that digital numbers from said source are inserted into said counter and said register, and clock pulse means connected to said counter to cause it to count at a prescribed rate from the value of the numbers inserted therein by said source to its count limit, said counter generating an output signal when said limit is reached, for timing the transmission of simulated radio navigation signals. As described, a Loran simulator comprises a general-purpose digital computer 11 whose output can be applied to a counter 12 or to a register 14, depending on the instructions and controls in the programme. A register 15 may be connected in series with the register 14. The outputs from the counter and the register are connected to respective inputs of a pulse generator 16, which supplies a standard Loran receiver 17. Output from the counter 12 is also applied to the computer 11, along a line 13. A ship's control panel 18 is located near the receiver 17, for operation by a trainee, and its output is applied through an interface 21 to the computer 11. An instructor's console 19 is also connected through the interface 21 to the computer 11. In operation, the computer is programmed to perform standard navigational computations using an initial position and ship characteristics selected by the instructor, and speed and direction particulars supplied by the trainee. The computer is also continually computing the relative amplitudes and timings of the signals which would be received from Loran transmitters in known positions by Loran receivers located at the computed position of the ship. Information fed into the counter 12 is in the form of a number which sets it, after which a fixed rate pulse generator drives it through its count until it reaches its limit, a time being taken which determines the time between the generation of successive Loran pulses by the generator 16. As several pairs of Loran transmitters having different pulse repetition rates are simulated, said time is continually changing. Information supplied by the computer 11 to the register 14, however, determines the characteristics of the pulse from the generator 16, such as, its size, shape and the number of reflections or ghost pulses. As shown in Fig. 1, when the capacity of the counter 12 is reached, and before the pulse generator 16 is triggered, an interrupt signal is sent to the computer 11 along the line 13. Upon receipt of this interrupt signal, the computer 11 immediately sends a new time delay word to the counter 12, and a corresponding characteristics word to the register 14. As the new characteristics word is entered into the register 14, an existing characteristics word therein is transferred to the register 15, and the pulse generator 16 then triggers. Detailed circuit diagrams for an embodiment having provision for simulation using either Loran-A or Loran-C signals are given (Figs. 2A to 2F, 3, 4, 5, not shown).