Patent GB-581603-A (GB)
Title: Improvements in or relating to wireless systems for navigation
IPC: G01S1/20
Filed: 1942-12-23
Abstract: 581,603. Radio navigation ; valve circuits. DIPPY, R. J. Dec. 23, 1942, No. 18288. [Class 40 (v)] [Also in Group XXXVI] Wireless navigation apparatus to enable an aircraft &c. to determine its position, or steer a desired course, with reference to two or more separate transmitters, comprises means for indicating or measuring the time interval between the reception of pulse signals, radiated from said transmitters and having a predetermined time relationship. The invention may be used with the main and satellite synchronized pulse transmitters described in Specification 581,602. Fig. 1 shows three transmitters A, B, C and two' series of curves representing paths along which there will be a certain constant time interval between the reception of counter. part pulses from stations A and B or A and C. A pilot at position P on curves B1, C1 can thus determine his position with reference to the three transmitters. Alternatively, he can " home " on to a given destination by steering consistently along one or other of the curves which pass through that point. Fig. 3 shows the receiving apparatus on the aircraft. Signals from the aerial AR and superhet receiver R pass to one of the vertical deflecting plates Y of the cathode-ray tube T, shift or vertical spacing voltages being fed to the other vertical plate at appropriate times from valve circuit V7 in order to produce three parallel time bases in which pulses from the three transmitters A, B and C appear individually as shown in Fig. 6 or Fig. 7. Locally generated pulses and deflecting wave-forms are applied to the C.R. tube to provide " strobe " markers and time bases to facilitate accurate observation of the three signal traces. The timing of the circuits is controlled by a crystal oscillator VC stabilized at 150 kc/s. from which are derived by frequency-dividers DV2 ... DV7 voltages of frequency 500 (the pulse repetition frequency of station A) which are passed by a diode V2 to control a saw-tooth oscillator V3, the output of which passes through paraphase amplifiers V4, V5 to the horizontal deflecting electrodes X, X to provide the main time base. A further frequency divider V1 supplies voltages of frequency 250 to valve circuit V7 (which supplies the shift voltages previously referred to) and to three relaxation oscillators V8, V9, V10 which generate square-topped " strobing " or timing impulses which can be adjusted to " straddle the A, B and C pulses as they appear on their respective traces. The strobing pulses are applied through a mixing valve V11 to the cathode of the tube T 'and appear as bright patches on each of the main traces. By moving switch ST1 into its lower position, the strobing pulses can be fed from mixer V11 to the saw-tooth generator V3 to produce highspeed traces on the tube T. The signal traces are thus enlarged (as shown in Fig. 6) to facilitate measurement of the significant time intervals. Calibration pulses at frequencies of 150, 15 and 1.5 kilocycles p.s. derived from the square pulse generator DV1 and the frequency dividers DV3, DV4, are led through valve circuit DV9 to the cathode of the C.R. tube and produce spaced marking indications P, Fig. 6, on the screen. Deriving stepped vertical shift voltage from pentode V7, Fig. 4. Square-wave pulses 1, Fig. 5, applied to the control grid of pentode V7 cause the potential of the screen grid to fall from point a in the curve 2, Fig. 5, to a fixed level b where it remains until, after a period determined by the tapping P7, the suppressor grid recovers its initial positive potential. Anode current then flows and the screen-grid potential rises sharply from the level be to a point d where it remains until the negative half-cycle of the applied impulse, whereupon the screen-grid potential rises from the level de to its intial level f, g and remains there until the next positive pulse initiates a new cycle. The stepped voltage shown in curve 2 is applied to one of the vertical deflecting plates as described above. Deriving pulsed wave-form 7, Fig. 5, from square wave-form 1 for production of strobing impulses. The square pulses 1 are applied to the control grids of three transitron -connected pentodes V8, V9, V10, Fig. 4, the anodes of which are connected through condensers C32, C33, C34 to the suppressor grid of a mixing valve V11, from the screen-grid of which the desired pulses are obtained. Wave-form 3, Fig. 5, is produced at the anode of V8, and waveform 4 from the anode of V9, the positions of the negative-going edges being determined by the potential dividers P9, P11. Wave-form 5 is produced at the anode of V10, being controlled by a pulse half a cycle out of phase with pulse 1, the position of the negative-going edge being controlled by the potential divider P13. The relative shape and spacing of the pulses applied to the suppressor grid, and taken from the screen grid, of valve V1 is shown at 6 and 7 in Fig. 5. Operation. The pulse frequency of transmitter A may be 500 p.s., and that of transmitters B and C may be 250, and to facilitate identification of the pulses, one of them, say that from B, may have a second " ghost " pulse associated with it as shown in Fig. 6. In operation, the maintrace, shown in Fig. 7, is first used and the received signals caused to drift along the traces by adjusting the oscillator VC until the A and B signals are on the top trace, with the A pulse located on the stepped portion. This automatically places the A1 and C signals on the lower trace. The oscillator is then adjusted to synchronism, so that the received signals remain stationary. The three " strobe " markers are moved along the traces, by adjustment of the potentiometers P9, P11, P13 until they straddle the A, B, C signals respectively. Switches SS1, ST1 are then operated to replace the main time bases by the three high-speed time bases corresponding to the three selected " strobe " positions, as shown in Fig. 6. Accurate measurement is now possible with the aid of the 150 kc/s. time markers. The arrangements of Figs. 3 to 7 also form the subject-matter of Specification 581,638 which is divided from the present Specification and the claims of which relate to the cathoderay oscillograph features.