Abstract :
Although the experimental electronic sector-scanning sonar equipment used in the earlier sea trials (reported in this Journal in November 1959) gave good results from the research point of view, and established the soundness of the theoretical studies, it had some serious defects from the practical point of view which showed up markedly when it was used operationally in December 1959 for studies of fish migration. Great improvements in the design have now been effected and are described in this paper. In particular, the use of the ¿re-modulation¿ process has enabled the full potential dynamic range of the receiver to be attained.
