Humminbird 343c manual How Sonar Works

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531447-1_A_343c_Eng.qxd 11/11/2005 9:18 PM Page 6

How Sonar Works

Sonar technology is based on sound waves. The 300 Series™ Fishing System uses sonar to locate and define structure, bottom contour and composition, as well as depth directly below the transducer.

Your 300 Series™ Fishing System sends a sound wave signal and determines distance by measuring the time between the transmission of the sound wave and when the sound wave is reflected off of an object; it then uses the reflected signal to interpret location, size, and composition of an object.

Sonar 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.

SONAR is an acronym for SOund and NAvigation Ranging. Sonar utilizes precision sound pulses or "pings" which are emitted into the water in a teardrop-shaped beam.

The sound pulses "echo" back from objects in the water such as the bottom, fish and other submerged objects. The returned echoes are displayed on the LCD screen. Each time a new echo is received, the old echoes are moved across the LCD, creating a scrolling effect.

When all the echoes are viewed side by side, an easy to interpret "graph" of the bottom, fish and structure appears.

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. Low frequencies (83 kHz) are typically used to achieve greater depth capability.

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Contents 343c Operations Manual Table of Contents Thank YouAlarms Menu Tab Setup Menu TabTroubleshooting Specifications Glossary Contact HumminbirdHow Sonar Works DualBeam Plus Sonar What’s On the Display High Sonar Intensity Return Bait BallViews Sonar ViewReal Time Sonar RTS Window Understanding Sonar HistoryFreeze Frame Bottom Presentation Sonar Zoom View 200/83 kHz Split Sonar ViewPOWER/LIGHT Key Big Digits ViewKey Functions Circular Flasher ViewWAY Cursor Control Key Menu KeyExit Key Powering Up the Unit Menu SystemExit Normal operation by powering your Fishing System off Start-Up Options MenuNormal Operation Normal Simulator System StatusSelf Test Accessory Test Exit the Simulator by powering your Fishing System offExit System Status by powering your Fishing System off SimulatorTo adjust the Sensitivity Sonar X-PressTMMenuSensitivity Highlight Sensitivity on the Sonar X-PressTMMenuTo adjust the Upper Range To adjust the Lower RangeUpper Range Lower RangeChart Speed Zoom LevelBottom Lock Bottom RangeSonar Menu Tab Beam SelectTo use Beam Select Highlight Beam Select on the Sonar main menuTo change the Fish ID Sensitivity setting To change the RTS Window settingFish ID+TM Fish ID SensitivityBottom View Zoom WidthKHz Sensitivity Depth LinesNoise Filter Surface ClutterMax Depth To change the Water Type setting Alarms Menu TabWater Type Depth Alarm Fish ID AlarmLow Battery Alarm Temp AlarmAlarm Tone Setup Menu TabTo change the Alarm Tone setting Highlight Alarm Tone on the Alarms main menuUser Mode Units DepthUnits Temp Units DistanceRestore Defaults Triplog ResetSelect Views Depth Offset Select ReadoutsTemp Offset To change the Speed Calibration setting TroubleshootingSpeed Calibration Display Problems Problem Possible CauseFinding the Cause of Noise IsolationGlossary SpecificationsSonar Terms 531447-1A343cEng.qxd 11/11/2005 918 PM 531447-1A343cEng.qxd 11/11/2005 918 PM Receiver See Transmitter 531447-1A343cEng.qxd 11/11/2005 918 PM Contact Humminbird