Operation Manual

8120 Installation and Operation Manual61
Press
SETUP
then select Sonar:
Frequency
There is a choice of: 200 kHz, 50 kHz and
Mixed. For information about selecting a
suitable frequency for the water conditions,
see section 8-3.
Scroll speed
Use this to set the scroll speed on the display.
There is a choice of: Very Fast, Fast,
Medium, Slow and Pause. The depth of
the water also affects the speed of the display.
Faster scroll speeds combined with a slow
boat speed (typically between 2 and 6 knots)
shows the most fish detail. Medium or Slow
scroll speeds result in sonar information being
displayed over a longer period, but with less
detail (see Section 8-2).
Fish symbols
The Instrument always displays echoes
from fish (fish arches, see section 8-4). If fish
symbols are on, a symbol is displayed over the
arch (see section 8-4). The options are:
• Off: No fish symbol is displayed.
• Fun or Normal: A fish symbol is displayed.
Fish depth labels
When this is turned on, the depth of a fish is
printed next to the fish arch.
Fish filter
Use this to select the minimum fish size
that will be displayed as a fish symbol and
to trigger the Fish alarm. The options are:
Small, Medium and Large.
17-3 Setup > Sonar
Fish sensitivity
Selects the minimum strength fish echo that
will be displayed as a fish symbol. Higher
values will display more fish symbols.
Digit size
Use this to remove or change the size of the
depth window on the sonar windows. There
is a choice of: Small, Medium and Large.
Palette
Use this to select a colour palette. Each colour
within the palette represents a different echo
strength, as shown on the sonar windows.
There is a choice of five colour palettes:
Black, Blue, White, Vivid and 8
colour. The first four pallettes display more
detail, and each colour covers a 1.5 dB signal
range. The 8 colour palette displays less
detail, and each colour covers a 3 dB signal
range.
Interference filter
No filter, normal setting.
Filters the echo signal to remove spiky
interference such as engine noise or depth
sounders on nearby boats.
Noise filter
Averages the echo signal to remove rapid
changes. Select Meduim or High to give a
smoother bottom trace–this may help to
detect a deeper bottom; however these
settings may also remove fish echoes. Select
Off for best fishfinding.
Surface clutter filter
Use this filter to hide the surface noise. Any
significant echoes (such as fish) will still be
displayed.
Pulse length
This can be used to specify the length of
the transmitted ultrasonic pulse. A short
pulse length improves the window detail but
contains less energy, therefore it does not
penetrate as deeply into the water as a longer
pulse.