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1.10 Suppressing Sea Clutter
In rough weather conditions returns from the sea
surface are received over several miles around
own ship and mask nearby targets. This situation
can be improved by properly using the automatic
anti-clutter function and/or the A/C SEA control.
Automatic anti-clutter control
The easiest way to suppress the surface clutter is
to use the automatic anti-clutter function. Press
the A/C AUTO switch.
CAUTION
The auto A/C function can erase weak
targets.
Manual anti-clutter control
From the fully counterclockwise position, slowly
turn the A/C SEA control clockwise. For opti-
mum target detection, leaves speckles of the sur-
face return slightly visible.
Sea clutter at
display center
Figure 1-8 Effect of A/C SEA control
The anti-clutter sea facility is often referred to as
STC (Sensitivity Time Control), which decreases
the sensitivity, and progressively increases the
sensitivity as the range increases.
If the control is set too low, targets will be hidden
in the clutter, while if it is set too high, both sea
clutter and targets will disappear from the dis-
play. In most cases adjust the control until clutter
has disappeared to leeward, but a little is still vis-
ible windward.
A/C SEA control adjusted;
sea clutter suppressed
A common mistake is too over-adjust the A/C
SEA control so that the surface clutter is com-
pletely removed. By rotating the control fully
clockwise, you will see how dangerous this can
be; a dark zone will be created near the center of
the screen, causing a loss of close-in targets. This
dark zone is even more dangerous if the gain has
not been properly adjusted. Always leave a little
surface clutter visible on the screen. If no clutter
is observed (on very calm waters), set the control
at the fully counterclockwise position.
1.11 Suppressing Rain Clutter
In adverse weather conditions, clouds, rain or
snow produce a lot of spray-like spurious echoes
and impairs target detection over a long distance.
This situation can be improved by using a Func-
tion key that is so programmed. If the Function
key fails to effectively suppress rain clutter, use
the A/C RAIN control.
The A/C RAIN control adjusts the monitor sen-
sitivity as the A/C SEA control does but rather in
a longer time period (longer range). Clockwise
rotation of this control increases the anti-clutter
effect.
Appearance of rain
clutter on the display
Figure 1-9 Effect of A/C RAIN control
A/C RAIN control adjusted;
rain clutter suppressed
1 – 11
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