491 Echo Sounder Operations Manual
Page 31
desired signal range, Signal Level completely removes the
weaker colors and their echoes.
To adjust the signal level:
1. On the
ECHO
screen, press
PICTURE
.
2. On the
PICTURE
screen, press
SIGNAL LEVEL
.
3. At the
SIGNAL LEVEL
window, 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
(minimum) to
5
(max-
imum). For example, if you select a signal level of
3
, echo
strengths of
0
through
3
are all displayed using the same
color.
4. Press
RETURN
to go back to the
ECHO
screen.
Suppressing interference (the noise limiter)
The
noise limiter
reduces the adverse effects of interference
from other nearby echo sounders or electronic devices.
however, the noise limiter may cause some very weak echoes
to be made smaller or 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
screen, press
PICTURE
.
2. At the
PICTURE
screen, press
NOISE LIMITER
.
3. At the
NOISE LIMITER
window, press the
CURSOR PAD
up to turn the noise limiter on (or press
NOISE LIMITER
again).
4. Press the
RETURN
key to go back to the
ECHO
screen.
Turning the noise limiter on changes a portion of the
PICTURE
key tab from green to yellow, as a reminder.
