Humminbird 997c SI Combo, Installation And Operation Manual

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Understanding Side Imaging
It is important to understand how Side Imaging technology produces the
display available on the 900 Series™. The images you see on the display are
produced using sonar technology. The special transducer produces three
distinct beams – one beam facing down and two beams pointing out to the
side. These “side beams” are aimed at right angles to the path of the boat and,
unlike the “down beam” which provide conical coverage, the side beams
provide coverage which is very thin front to back, yet very wide top to bottom.
The narrow aspect (front to back) of the beam illuminates a small strip of the
bottom perpendicular to the direction of the boat. Each time the unit “pings”, a
strip of data representing all the echoes received by the transducer, are put
together on the display to form the image that you see. The rows closest to the
boat icon at the top of the display are the most recent sonar data. The
information is scrolled down the screen as new data, drawn at the top of the
screen, becomes available.
The side beams can be operated at one of two frequencies: 455 kHz
or 800 kHz. Selecting 800 kHz produces the sharpest image while selecting
455 kHz provides greater bottom coverage area. It is important to understand
that when the boat turns, the strips to one side will begin to overlap and the
strips on the other side will fan out, providing some distortion to the image.
Side beams look out 360 feet, with a depth limitation of 100 to 150 feet,
depending on the contour of the bottom and when the side beam frequency
selection is set for 455 kHz. Please see the
Side Imaging Sonar Tutorial at
www.humminbird.com for a more detailed explanation.
Your Side Imaging transducer also provides traditional sonar imaging at
200/83 kHz.
455 kHz provides maximum coverage with 180° total beam width
800 kHz provides highest resolution with 130° total beam width
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