• | TVG (Time Variable Gain) When an acoustic pulse is sent through the water, it will gradually lose its energy. The greater the distance between the transducer and the target(s), the greater the loss of energy. TVG (Time Variable Gain) compensates for the loss of acoustic energy due to geometric spread and absorption.
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• | Ping-Ping Filter The Ping-Ping Filter analyses the historical information from previous consecutive pings in order to remove unwanted noise and false echoes from
the ST90 presentation.
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• | Pulse Type The Pulse Type function allows you to select the "shape" of the transmitted pulses ("pings"). Different shapes have different qualities. Which pulse type to use depends on the current environmental conditions, your range to the target(s) and the type and speed
of the target(s) you are observing.
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• | Bandwidth The Bandwidth function allows you to select the frequency range in the Hyperbolic Frequency Modulated (HFM) transmissions.
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• | Frequency The Frequency function allows you set the centre frequency for the Hyperbolic Frequency Modulated (HFM) and Linear Frequency Modulated
(LFM) transmissions (pings), and the operating frequency for the Continuous Wave (CW) pings.
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• | Horizontal TX Sector The ST90 transmits in a swath with maximum horizontal opening angle 360° omnidirectional. By means of the Horizontal Tx Sector function, you can change this opening angle to 180, 120, 90, 60 or 30°. The function is only available in the Horizontal, Plane and Inspection views.
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• | Vertical TX Sector The ST90 transmits in a swath with maximum vertical opening angle 94°. By means of the Vertical Tx Sector function, you can change this opening angle to N/A. The function is only available in the Vertical and Navigation views.
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• | Range Projection The distance to a target located anywhere in the water column can be measured in two ways. This can either be the horizontal distance to the target (True), or along the tilt angle (Slant). The Range Projection function defines how this distance is measured.
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• | AGC (Automatic Gain Control) The AGC (Automatic Gain Control) function runs an automatic analysis of the echo strength.
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• | RCG (Reverberation Controlled Gain) The RCG (Reverberation Controlled Gain) function removes unwanted reverberation from the bottom and or from the sea surface. This enhances the visibility of schools. It may however also remove scattered fish from the presentation.
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• | Bottom Filter Threshold The ST90 provides a bottom filter to reduce the sometimes powerful echo from the seabed. This filter is useful if you try to find fish close to the bottom. Select a Bottom Filter Threshold value to control the "strength" of the filter. A higher numerical increases the filter efficiency and reduces the bottom echo accordingly.
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• | Noise Filter The Noise Filter removes unwanted acoustic noise from the ST90 presentation. It reduces the interference from other acoustic systems (sonars and echo sounders), as well as the noise from the propellers.
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• | Horizontal Scroll The Horizontal Scroll function controls how fast the echo presentation shall move from right towards left in the Echogram view. The "speed" is controlled by adjusting the number of pixels used to present each ping. A higher speed reduces the resolution.
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• | Vertical Reference The function is only available in the Vertical view, as well as the vertical Navigation view.
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