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491 Echo Sounder Operations Manual Page 29
3. At the GAIN window, press the CURSOR PAD left or right
to adjust the gain, or use the KEYPAD to manually enter
the desired gain value. The available settings range from
zero (minimum) to 75 (maximum).
Gain window
The window shows the effect of adjusting the gain. The
fish symbols near the bottom of the window represent
various echo strengths, and the expanding and
contracting color bar above shows the colors that will be
used to display these echoes. As you adjust the gain to
obtain the best looking picture, also watch the real echoes
on the right side of the screen .
4. Press RETURN to go back to the ECHO screen.
When you adjust the gain, the color of the AUTO and
PICTURE key tabs changes from green to yellow, since
the echo sounder is no longer in automatic mode. Also, a
yellow tab appears under the DEPTH key, indicating that
the range setting is no longer automatically controlled and
that the 491 may not always identify the bottom reliably.
Adjusting the clutter (weak echoes)
The clutter setting selects the echo strength that will be
displayed using the bottom colors of the color bar (the weaker
echoes). Any echoes weaker than this selection will not be