A multi-channel general purpose research echo sounder

A deep-towed, multi-channel echo sounder has been developed for use as a general purpose acoustics research tool. The unit is capable of arbitrary waveform generation and broadband signal detection. It has initially been configured to transmit on eight discreet frequencies between 50 kHz and 1 MHz for use in zooplankton backscatter studies. Each received signal is synchronously demodulated and digitized at a rate of 125 kHz. The transceiver unit can be towed to depths of 300 meters using an unfaired single coaxial tow cable that supplies power to the towed unit and carries bidirectional data and control signals at rates of up to 1 Mbit per second. The surface unit consists of a power supply, with telemetry unit, coupled to a 486 based PC. The PC controls the operation of the towed transceiver, and logs the uplinked digitized acoustic signals. Acoustic and engineering data are displayed in real time. Efficient use of spectral space in the communications link permits future addition of video and instrumentation channels