Humminbird 900 Series, 997c Combo manual High Definition Side Imaging Sonar

The sound pulses are transmitted at various frequencies depending on the application. Very high frequencies (455 kHz) are used for greatest definition but the operating depth is limited. High frequencies (200 kHz) are commonly used on consumer sonar and provide a good balance between depth performance and resolution. Low frequencies (83 kHz) are typically used to achieve greater depth capability.

The power output is the amount of energy generated by the sonar transmitter. It is commonly measured using two methods:

•Root Mean Square (RMS) measures power output over the entire transmit cycle.

•Peak to Peak measures power output at the highest points.

The benefits of increased power output are the ability to detect smaller targets at greater distances, ability to overcome noise, better high speed performance and enhanced depth capability.

High Definition

Side Imaging Sonar

Your 900 Series™ 997c SI Combo uses Side Imaging sonar to provide a wide yet precise survey of a large area of water, including detailed bottom topography and fish-attracting structure orientation. The Side Imaging transducer returns are processed into an image similar to an aerial photograph. Typically, the Side Imaging sonar can search an area that is 720 feet wide (360 to each side), with a typical depth performance of 150 feet when the Side Imaging Sonar frequency is set for 455kHz. The side beams can be operated at one of two frequencies: 455 kHz or 800 kHz. Selecting 800 kHz produces the sharpest image but the search area to each side and the depth capability are limited as compared to the 455 kHz frequency. See What’s on the Side Imaging Display and Understanding Side Imaging for more information.

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