Stc (Sensitivity Time Control) - Standard Horizon FF525 Operation Manual

4.6.1

STC (Sensitivity Time Control)

The STC function attenuates echos from surface down to the specified STC depth by
changing the sensitivity of the receiver, decreasing it near the surface and gradually
increasing it as the depth increases. STC impacts bottom finding so it can be particularly
useful to track a rocky sea bottom distinguishing it from mud in suspension over it. For
example when close to rivers outlet to the sea (consider to use at same time also Dual
Frequency mode and White Line for an easier identification of real sea bottom), as well as
to solve issues in false bottom detection when in presense of significant surface clutter
(reading shallow, example 3Ft).
Its default value is SHORT for the 200 kHz frequency and MID for the 50 KHz frequency.
Such values are good in most conditions. However when navigating in very shallow waters
it may be necessary to switch it to OFF, while in very deep waters with a lot of Surface Clutter
it may be better to increase it to MID or LONG.
In some situations it may be necessary to adjust the STC so the sounder can read through the
surface noise and show the bottom. One indication that the STC needs to be changed is when the
display intermittently changes the depth from the correct depth to a very shallow depth.
The STC can be changed from Short, Mid, Long and Custom.
· STC Length
This is the depth range which the STC operates. In custom mode it can be varied from
0Ft to 1000Ft (60Ft or 255Ft on previous software versions). In preset mode it's value
is reported in the following table.
· STC Strength
It is the starting attenuation value of the STC. It acts by attenuating the Gain of the given
percentage value. In custom mode it can be varied from 0% to 100%. The STC effect
is maximum near the surface, to mitigate the Surface Clutter and it progressively
diminishes to 0 at the selected STC depth.
· Preset values table
When in shallow water and the Fish Finder display is showing a bottom or digital
readout deeper than the actual depth this situation may occur if STC is set to LONG
or MID when the bottom is shallow. This issue may be resolved by adjusting the STC
value to SHORT or even to OFF in very shallow waters.
CP and FF525 Operation Manual
NOTE
Figure4.6.1 - STC - Surface Clutter
Figure 4.6.1a - STC Preset values table
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