GB873806A - Improvements in or relating to echo sounders - Google Patents

Abstract

873,806. Echo sounders. MARCONI'S WIRELESS TELEGRAPH CO. Ltd. Sept. 10, 1959 [Feb. 13, 1959], No. 5178/59. Class 40(7) An echo-sounder comprises two transmitreceive transducers with their pressure wave surfaces spaced apart in the direction of propagation by an amount substantially differing from one half-wavelength, and multiples thereof, at the operating wave frequency, means for simultaneously actuating the surfaces by A.C. pulses from a source, and a receiver input circuit coupled to the actuating means and coupled to the source such that pulses therefrom produce substantially no voltage across that circuit. Shallow-water depth sounding and fish finding is thus rendered possible. In the first embodiment, Fig. 1, pulses at an ultrasonic frequency are applied at terminals 1, 1 and transformers 2, 3 are connected such that the pulses at points 4, 4 are in phase with amplitudes equalized by adjustment of components 5, 6; thus no input from the source arises at receiver input terminals 8, 8. The spacing between magneto-strictive transducers 9, 10, preferably #/8, ensures that echo inputs at points 4, 4 are not in phase. In the second embodiment; Fig. 2, a single transformer 11 and a 180 degrees phase shifter 12 are utilized, an attenuator 13 balancing the attenuation in the phase shifter; alternatively, the 180 degrees phase shift may be distributed between the output lines to terminals 4, 4. The transducers may be combined into a single structure.