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CPF180i and CPF300i Page 121
NOTE
When the Gain Mode option is set to Auto, the receivers Gain cannot be changed.
When the Gain Mode option is set to Manual, the Gain can be manually adjusted. When switching
from Automatic to Manual Mode, the Gain + Offset value is copied into the Manual Gain setting of
the receiver.
17.10.1 STC (Sensitivity Time Control)
The purpose of this selection is to filter surface noise in the water.
The STC functions reduces or eliminates Surface Clutter signals by changing the Sensitivity
of the receiver, decreasing it near the surface and gradually increasing it as the depth
increases. Its default value is SHORT for the 200kHz frequency and MID for the 50KHz
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.
NOTE
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.
Figure 17.10.1 - STC - Surface Clutter
The STC can be changed from Short, Mid, Long and Custom.
17.10.1.0 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 (See Par. 17.10.1.2).
17.10.1.1 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 eliminate the Surface Clutter and it progressively diminishes
to 0 at the selected STC depth.