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491 Echo Sounder Operations Manual
displayed. If you select
5
, for example, all weak and moderate
echoes will be displayed using the background color (just as if
they weren’t there). You might choose this setting to eliminate
high levels of background noise and echoes from turbulence
or plankton. A setting of
0
allows all echoes to be displayed.
To adjust the clutter:
1. At the
ECHO
screen, press
PICTURE
.
2. At the
PICTURE
screen, press
CLUTTER
.
3. Press the
CURSOR PAD
left or right to adjust the clutter,
or use the
KEYPAD
to manually enter the desired clutter
value. The available settings range from zero (minimum)
to nine (maximum).
Clutter window
4. Press
RETURN
to go back to the
ECHO
screen.
When you adjust the clutter, the color of the
AUTO
and
PICTURE
key tabs changes from green to yellow, since
the echo sounder is no longer in fully automatic mode.
Adjusting the signal level (weak echoes)
As with the
CLUTTER
key, the
SIGNAL LEVEL
key controls
the appearance of low level noise in the picture. Whereas
clutter compresses or expands the available colors to fit the
