FF520
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when the water is full of materials in suspension, with bad sea conditions.
7.6
WHAT SHOULD I DO IF THE AUTO MODES FAIL?
Failure of auto modes can happen for various reasons. Hereafter you can find a range of
possibilities.
7.7
AUTO-RANGE FAILS IN VERY SHALLOW WATERS DIS-
PLAYING A DIGITAL DEPTH READOUT DEEPER THAN THE
ACTUAL VALUE. WHAT SHOULD I DO?
This usually happens if the STC is set to LONG or MID and the bottom is shallow or SHORT
if the bottom is very shallow causing the auto-range to hook to the second or third echo from
the bottom (since in shallow waters the sound bounces more times back and forth the
surface to the bottom). Try decreasing the STC value to SHORT in shallow waters or to
switch it to VERY SHORT or OFF.
7.8
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.
7.9
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.
7.10 AT A VERY SHALLOW RANGE UPPER HALF OF THE SCREEN
APPEARS ALMOST COMPLETELY FILLED BY THE SUR-
FACE 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
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