Humminbird ] 981 - Manual (Page 69)

50 KHZ SENSITIVITY
(Advanced)
50 kHz Sensitivity changes the sensitivity of the 50 kHz beam. Increasing the 50 kHz
Sensitivity will display additional weak returns and decreasing the 50 kHz Sensitivity
will display fewer weak returns. The 50 kHz Sensitivity menu choice is only available
when User Mode is set to Advanced (see Setup Menu Tab: User Mode).
To set the 50 kHz Sensitivity:
1. Make sure you are in Advanced User Mode, then highlight 50 kHz Sensitivity on
the Sonar main menu.
2. Use the LEFT or RIGHT 4-WAY Cursor Control keys to set the 50 kHz Sensitivity. (-
10 to +10, Default = 0)
DEPTH LINES
(Advanced)
Depth Lines divide the display into four equal sections that are separated by three
horizontal depth lines. The depth of each line is displayed along the depth scale. You
can either turn Depth Lines On or Off. The Depth Lines menu choice is available when
User Mode is set to Advanced (see Setup Menu Tab: User Mode).
To change the Depth Lines setting:
1. Make sure you are in Advanced User Mode,
then highlight Depth Lines on the Sonar main
menu.
2. Use the LEFT or RIGHT 4-WAY Cursor Control
keys to turn the Depth Lines setting On or Off.
(Off, On, Default = On)
SURFACE CLUTTER
(Advanced)
Surface Clutter adjusts the filter that removes surface clutter noise caused by algae
and aeration. The lower the setting, the less surface clutter will be displayed. The
Surface Clutter menu choice is available when User Mode is set to Advanced (see Setup
Menu Tab: User Mode).
To change the Surface Clutter setting:
1. Make sure you are in Advanced User Mode, then
highlight Surface Clutter on the Sonar main menu.
2. Use the LEFT or RIGHT 4-WAY Cursor Control
keys to change the Surface Clutter setting. (Low =
1 to High = 10, Default = 5)
NOISE FILTER
(Advanced)
Noise Filter adjusts the sonar Noise Filter to limit interference on the display from sources
such as your boat engine, turbulence, or other sonar devices. The Noise Filter menu choice
is available when User Mode is set to Advanced (see Setup Menu Tab: User Mode).
NOTE: The Off setting removes all filtering; Low, Medium and High settings add progressive
filtering of the sonar returns. In some deep water situations, the High setting may actually
make it harder for the control head to find the bottom.
To change the Noise Filter setting:
1. Make sure you are in Advanced User Mode, then highlight Noise Filter on the
Sonar main menu.
2. Use the LEFT or RIGHT 4-WAY Cursor Control keys to change the Noise Filter
setting. (Off, Low, Medium, High, Default = Off)
Surface Clutter
Depth Lines
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