Patent GB-752629-A (GB)
Title: Improved simulated high frequency radio receiving apparatus for aircraft trainers
Inventor: GALLO JOSEPH EDWARD
IPC: G09B9/26
Filed: 1954-10-08
Abstract: 752,629. Trainers for radio navigation. CURTISS-WRIGHT CORPORATION. Oct. 8, 1954, No. 29112/54. Class 40 (7). An arrangement simulating the operation of radio receiving apparatus for use in an aircraft training device includes means for deriving one electrical signal related to simulated craft altitude, a second signal related to simulated range from a radio transmitter, and means controlling the operation of the receiving apparatus in response to the amplitude and sense of the difference between these signals to give an operation similar to that to be expected at the given altitude and range. The embodiments indicate how radio communication or radio navigation signals may be gradually or suddenly cut off as the simulated range and height of the craft puts it below the extreme line of sight from the transmitter. Range and altitude information may be fed in as the angular settings of the potentiometers fed with oppositely phased A.C. signals. The signals tapped off from the potentiometers are combined through proportioning resistor circuits and applied to the grid of a valve whose anode output is an A.C. signal depending in polarity (phase) and amplitude on whether the craft is above or below the extreme line of sight and to what extent. This output signal is applied to a phase-sensitive rectifier to give a corresponding rectified output which may be used to control a relay which cuts off the output of the simulated radio apparatus when the craft is below the extreme line of sight (Fig. 1, not shown). Alternatively the rectified signal, derived at the point 231 (Fig. 2), may be fed through resistor 301 to control the gain of valve V6 through which the simulated radio signals are passed. As the craft proceeds out of the line of sight range negative bias is increasingly applied from 231 to the grid of V6 and the valve eventually cuts off. The lower part of Fig. 2 shows a voltage resolver 32 controlled by the pupil in accordance with his selected course and fed with signals representing radio-navigational information. The output of secondary winding 36 (representing deviation from a desired course) is fed through valve V7 and phase-sensitive rectifier 40 to control the needle 42 of cross pointer meter 43. The gain of valve V7 is likewise controlled according to the potential at point 231 and the signal fed to the meter fades away as the craft proceeds out of the line of sight range. A warning indicator 45 held in its inoperative condition by current through coil 47 tapped out from the cathode resistor of valve V7 falls to show the meter is inoperative when V7 is biased off. The output from secondary winding 35 (representing the distance to the transmitter) is fed through a similar valve V<SP>1</SP>7 and another phase sensitive rectifier 40<SP>1</SP> to control an indicator 44 which operates to inform the pupil that his simulated position is over (or close to) the transmitter. Valve V<SP>1</SP>7 is likewise controlled from point 23<SP>1</SP> to simulate the operation of indicator 44 under no-signal conditions.