Raymarine e7 User Reference page 203

The new values remain set even when you switch off the display
and are applied to all fishfinder windows.
Fishfinder TVG (Time Varied Gain)
The Time Varied Gain (TVG) function reduces the amount of clutter
in the fishfinder display by varying the gain throughout the column of
water. This function is useful for reducing the appearance of 'noise'.
• Increasing the TVG value increases the maximum depth to which
TVG is applied. A high value decreases the gain in shallow water
so that only the strongest echoes are displayed.
• Decreasing the TVG value reduces the maximum depth. A low
TVG value has little effect on gain in shallow water.
TVG adjustment can be made automatically or manually.
Adjusting the fishfinder time varied gain
From the fishfinder application:
1. Select Menu.
2. Select Adjust Sensitivity.
3. Select TVG.
4. Select the TVG menu so that Man is highlighted.
Selecting the TVG menu will switch between TVG Auto and
Manual modes.
5. Use the Rotary Control to adjust the TVG to the required setting.
Note: TVG has no effect in fishfinder simulator mode.
Using the fishfinder
Fishfinder color threshold
The color threshold setting determines the range of colors used on
screen. The effect of this is to set a color threshold below which
targets are not shown. For example a low setting would result in
only the strongest (orange and red) targets being displayed.
Adjusting the fishfinder color threshold
From the fishfinder application:
1. Select Menu.
2. Select Adjust Sensitivity.
3. Select Color Threshold.
4. Select the Color Threshold menu so that the setting is
highlighted.
5. Use the Rotary Control to adjust the color threshold to the
required setting.
6. Press the Ok button, or select the Color Threshold menu again
to confirm the setting.
Fishfinder power
The power setting controls the power level of the transducer.
Power options:
• Auto. This is the default setting. When it is selected the DSM
automatically determines the required power setting based on the
current depth, speed, and (bottom) signal strength. .
• Manual. If you wish to manually adjust the power to suit current
conditions, you can adjust the power level between 0% and
100%, in 10% increments. Lower power levels are normally used
in depth ranges less than 8 ft. (2.4 m) and higher power levels are
typically selected for depths greater than 12 ft. (3.7 m).
Adjusting the fishfinder power
From the fishfinder application:
1. Select Menu.
2. Select Adjust Sensitivity.
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