Chapter 6
CVS-833/833C
Using the Menu
Initial setting: 0
Control range: 0 - 20
STC is an abbreviation of Sensitivity Time Control, which is used to reduce weak echoes such as
plankton, floating marine plants, etc. near the sea surface in order to view a school of fish in good clarity.
The rate of sensitivity reduction is in log law, which can be adjusted in depth and in amplitude. Relation
between the STC law and resultant image display is shown in Figure 6.5 and 6.6.
6.6.1 Adjusting STC amplitude
In this mode, you are reducing receiver sensitivity in time proportional law with STC depth fixed. This
mode is useful in shallow water fishing to gain a better view of a school of fish near the sea surface.
STC Amplitude
C
B
A
Depth
STC
0
B C
A
Max
Max
Figure 6.5 Adjusting the STC amplitude
Operational notes for STC amplitude adjustment
(1) STC law A: STC is not enough, causing noise and unwanted residual weak echoes near the sea
surface are still shown.
(2) STC law B: STC is appropriate, causing unwanted echoes are perfectly reduced while schools of
fish are shown without degradation.
(3) STC law C: STC is too much, causing the echoes of fish school are reduced too much.
6.6.2 Adjusting STC depth
In this mode, you are reducing receiver sensitivity to depth in time proportional law with STC amplitude
fixed. This mode is useful in deep sea fishing to locate school of fish and the species.
0
STC
Depth
Max
C
B
A
STC Amplitude
Max
Figure 6.6 Adjusting the STC depth
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