Humminbird 47 Fish Finder User Manual


 
2
How Sonar Works
Sonar uses sound waves to determine the presence and location of underwater objects. The
time measured between the transmission of the sound wave and the reception of any
reflection can be used to determine distance from an object. Analysis of the reflected signal
can also be used to determine location, size, or composition of underwater objects.
Humminbird® products consist of two main components: the sonar unit and the
transducer. The sonar unit contains the transmitter and receiver, as well as the user controls
and LCD display. The transducer is mounted beneath the water surface and converts
electrical energy from the transmitter into mechanical pulses or sound waves. The
transducer also receives reflected sound waves and converts them back into electrical
signals for display on the sonar unit.
The transmit and receive cycle is very fast. A sound wave can travel from the surface to a
depth of 240 ft (70 m) and back again in less than
¹⁄₄
of a second. It is unlikely that your boat
can "outrun" this sonar signal.
A number of variables affect the nature of information which can be derived from the sonar
return. Sonar signals generated at a higher frequency have the advantage of greatly increased
sonar resolution, although the distance (depth) a high-frequency signal can travel is relatively
short. A low frequency signal can travel great distances, but provides poor sonar resolution. The
shape of the transmitted sonar signal greatly affects the information available as well. A single
wide beam has a large area of coverage but poor resolution of detail. A narrow beam has
excellent detail, but only a limited area of coverage.
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3D Sonar
Your Matrix™ Fishing System uses a six-element transducer that
transmits at 455 kHz and is capable of reaching depths of 240 ft
(75 m). Each transmitted beam is 16 degrees in width and is
symmetrical. The six beams are lined up next to each other to
provide a total coverage of 53 degrees from side to side, and 16
degrees from front to back. Using multiple narrow beams together
gives you a wide area of coverage for terrain interpretation and fish
location, without sacrificing the detail only a narrow beam can
provide. Your Matrix™ Fishing System gathers information from a
continuous series of these returned signals. It then interprets this
information to create a detailed 3-dimensional view of the terrain
passing beneath your boat as you travel across the water.
2D Sonar
Your Matrix™ Fishing System also has the capability of displaying
traditional 2-dimensional sonar information from either a 455 kHz
beam or an 83 kHz beam. The 455 kHz single beam has the
advantage of providing increased sonar resolution but is limited to
a depth capability of 240 ft (75 m). The 83 kHz single beam sonar
has the advantage of providing sonar information to 1000 ft
(330 m) but the sonar resolution is not as great as with the 455 kHz
single beam.
NOTE: Depth capability is affected by such factors as boat speed, wave
action, bottom hardness, water conditions and transducer installation.
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