A Versatile Sonar System for Fisheries Research and Management Applications

An echo sounder has been developed with features ideally suited to the fisheries researcher and fisheries manager. Instruments commonly used for fisheries management and research are inaccurate, limited in dynamic range, unstable, and generally inflexible. An effort has been made to overcome these difficiencies with the echo sounder described in this paper. The echo sounder to be described has a time-varied-gain receiver (
20 \log_{10} R
or
40 \log_{10} R + 2\alphaR
) accurate to within
\pm 0.5
dB over a 100-dB range. The equivalent dynamic range is 140 dB (the ratio of the maximum signal at minimum gain to the equivalent input noise at maximum gain in a 4-kHz bandwidth). The temperature stability is
\pm 0.5
dB from
10\deg
C to
35\deg
C at any range. Operating parameters, including frequency, can be easily altered to accommodate a variety of needs.