Standard Horizon FF525 Operation Manual page 28

5.7 Auto Range fails, and the digital depth readout displays a very shallow
reading. What should I do?
This usually happens if the STC is off or is set to a low value causing disturbance from
Surface Clutter to be stronger than bottom echoes. Try increasing the STC value. As general
rule STC has to be set as in shallow waters and LONG in depth waters.
5.8 Auto Range fails in very deep waters displaying a digital very shallow
depth readout. What should I do?
The Fish Finder capability to detect the bottom decreases as the bottom depth increase. If
the bottom composition is soft as mud, if the sea conditions are bad, if there are thermoclines
or the water is full of materials in suspension it can further decrease thus causing the digital
depth readout to fail. When this happens the Auto Range algorithm also fails. To recover
from this situation it is necessary to switch to Manual Range mode and to set the Manual
Depth mode. When Manual Depth mode is selected the algorithm that calculates the digital
depth readout searches for the bottom within the range manually selected by the user. At
this point it is necessary to increase manually the Range until the bottom becomes
graphically visible. If the echoes from the bottom are strong enough, the Fish Finder shall
look to the bottom giving a correct depth reading and shall be possible to return in Auto Range
mode. Please note that if one or more of the conditions that reduce the echoes from the
bottom listed above is true the bottom may be not visible at all, in this situation a strong
thermocline or Surface Clutter may be interpreted by the Fish Finder as the bottom.
5.9 At a very shallow range upper half of the screen appears almost
completely filled by the Surface Clutter. How can I eliminate it?
This is normal in shallow waters. To clean up the Surface Clutter without degrading the digital
depth readout algorithm functionality there are two modes: 1) If Surface Declutter = OFF it
is possible to set the STC value to custom setting the STC length to the same size of the
Surface Clutter, and increasing the STC strength until the image on the screen cleans up.
Please note that in very shallow waters it is usually better to switch to Manual Gain mode
to reduce Gain fluctuation due to rapidly changing bottom conditions. 2) Using Surface
Declutter, increase the Surface Declutter value until the Surface Declutter disappears
completely.
5.10 Why do I never see fishes in the range between 0 to 2Ft?
The minimum range of the Fish Finder is 2Ft. In this interval the Fish Finder can detect neither
the bottom nor any target.
5.11 How can I reduce the Surface Clutter?
You can act by: properly setting the STC as described at 7.10 and also by increasing the
NOISE LEVEL and reducing the GAIN or the GAIN OFFSET (if you are in Auto Gain mode).
However please note that a strong attenuation of Surface Clutter may also reduce the
capability to detect targets.
5.12 The Fish Finder is in Auto Gain mode but the picture display too many
small targets, what shall I do to reduce the screen clutter?
Try increasing the NOISE LEVEL or decreasing the GAIN OFFSET.
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