GB711139A - Improvements in echo sounding apparatus - Google Patents

Abstract

711,139. Pulse-radar. SOC. GENERALE D'ELECTRICITE ET DE RADIO. Jan. 23, 1951 [Jan. 25, 1950], No. 1702/51. Class 40 (7). [Also in Groups XXXVI and XXXVIII] In a pulse-echo ranging system the timing of the system is controlled by a master oscillator feeding a chain of 2:1 frequency dividers with square-wave outputs. The invention is described as applied to a subaqueous sounding system having a cathode-ray tube for displaying the location of shoals of fish but it may be applied to systems utilizing light or radio waves and an electromechanical indicator or recorder may be employed. As shown in Fig. 1 the 294 c/s sinusoidal output from the master oscillator 22 is squared at 23 and applied to a chain of frequency halvers 24a-24b, the outputs from selected frequency dividers being applied (a) via a pulse-recurence frequency selector 27 to trigger a pulse generator 28 whose output triggers the transmitter 29, (b) via a time-base selector 26 to trigger the vertical time-base of the cathode-ray tube 33, (c) via a marker selector 25 to the X plates of the tube and (d) to a selector 30 having two square-wave outputs, one, 30a, being applied to displace the time-base horizontally and the other, 30b, being applied as a blanking control to the grid of the cathode-ray tube; the latter output may also be applied to gate the receiver 31 whose output is applied to the grid and to the X plates of the cathode-ray tube. By these means the recurrence frequencies of the transmitted pulses, the time-base, the marker pulses and the blanking and displacement waves may be selected independently and the form of the display may be varied to suit particular requirements, e.g. if the recurrence frequency Fd of the trace displacement wave is the same as that of the time-base, Fs, a stepped trace results, Fig. 3 (not shown), but if Fd = Fs/2 a double trace results, Fig. 4 (not shown), and if the displacement wave Fig. 5c is formed by adding two square waves a and b having recurrence frequencies Fs/2 and Fs/4 respectively four parallel traces d result. In Figs. 4 and 5 the transmitter recurrence frequencies Ft would be Fs/2 and Fs/4 respectively so that the total range is spread over the multiple traces. Alternatively a selected fraction 1/2", of the total range may be displayed ; e.g. if the blanking waveform, Fig. 6c, is formed by adding two square waves a and b having recurrence frequencies Ft and 2 Ft respectively, three quarters of the trace will be blanked out and if Fs = 4 Ft, the remaining quarter will be expanded to full amplitude. When an electromechanical indicator or recorder is employed, it is driven by a motor synchronized by a selected output from the frequency dividers.