Improvements in and relating to echo sounding for use in deep sea fishing

摘要

1,101,755. Echo sounding. ATLAS-WERKE A.G. 5 May, 1965 [5 May, 1964], No. 18975/65. Heading H4D. In an ultrasonic echo-sounding method for indicating fish near the sea-bed, a pair of pulses of the same carrier frequency, the first pulse being weaker than the second pulse, is transmitted in each sounding period, and the seabed echo of the first pulse initiates the movement of the pen of a chart recorder or the luminous spot of a cathode ray tube so as to record the fish echoes and sea-bed echo of the second pulse. The interval between the two transmitted pulses, which is small compared with the sounding period, is so chosen with regard to the sea depth, the angular width of the conical sounding beam, and the distance between the fish and the sea-bed, that the echoes produced by the second pulse arrive at the echo sounder receiver after the reverberation of the sea-bed echo of the first pulse has died away at the receiver and before the second sea-bed echo of the first pulse arrives at the receiver. Numerical examples of the pulse periods and echo times are given for a sounding beam of semi-apex angle 15 degrees.