Fishing and Gear Technology

Unit 16 - Electronic equipments for fishing

16.7.SONAR

The sonar is a term used in World War II. It is an acronym for Sound, Navigation and Ranging. Lewis Nixon invented the first Sonar type listening device in 1906. The first Sonar devices were passive listening devices in which no signals were sent out. In active SONAR signals are sent out and received back. Sonar is capable of transmitting and receiving the sound pulse in horizontal direction. As in echo sounder the sonar also has four main components, the transmitter, the transducer, the receiver and the recorder or display.
Sonar can be described as a horizontally scanning echo sounder. Its transducer is fixed to a pipe which can be lowered or raised within a longer cylinder located below the hull. This can scan either side of the vessel or through 360º with free sight in all directions. Sonar can be tilted up and down from +10º to -90º. The train and tilt are remotely controlled from the bridge. Information is displayed in a plan position indicator (PPI) display as in; radar or in a Cathode Ray Tube (CRT).