NorthStar 972, Quickstart Manual And Reference Manual

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115
Reference section 7 — Echo sounding
The picture menu Reference Manual Revision B
2. Press
Clutter
.
3. Press the cursor pad up or down to adjust the
clutter, or use the keypad to manually enter
the desired clutter value. The available set-
tings range from zero (shows all echoes) to
nine (suppresses many echoes).
4. Press
Return
to go back to the Echo
Sounder screen.
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 desired signal range, Signal Level
completely removes the weaker colors and
their echoes.
To adjust the signal level:
1. On the Echo Sounder screen, press
Picture
.
2. Press
Signal level
.
3. Press the cursor pad up or down to remove
the weaker color levels from the picture, or
use the keypad to manually enter the desired
signal level.
The available settings range from
1
(mini-
mum) to
5
(maximum). For example, if you
select a signal level of
3
, echo strengths of
0
through
3
are all displayed using the
same color as the background.
4. Press
Return
to go back to the Echo
Sounder screen.
Suppressing interference (the noise
limiter)
The noise limiter reduces the adverse
effects of interference caused by other
nearby echo sounders or electronic
devices. However, the noise limiter may
cause some very weak echoes to be made
smaller or be entirely eliminated, since it
removes any echoes that aren’t sustained
for at least two pings.
To turn on the noise limiter:
1. At the Echo Sounder screen, press
Picture
.
2. Press
Noise
to turn the limiter on or off.
3. Press the
Return
key to go back to the Echo
Sounder screen.
Selecting the color bar (hue) and
white level
The color bar displayed at the extreme left
of the
Echo Sounder
screen shows the range
of colors used to display various echo
strengths. Weaker echoes are displayed
with colors near the bottom of the scale,
and stronger echoes are displayed with
colors near the top.
You can choose any one of nine palettes of
colors to represent the echo strengths from
weakest to strongest.
•
Color bar #1 is the one most often
used.