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2-5
How to adjust STC (suppressing
sea clutter)
Echoes from waves can be troublesome,
covering the central part of the display with
random signals known as sea clutter. The
higher the waves, and the higher the
antenna above the water, the further the
clutter will extend. Sea clutter appears on
the display as many small echoes which
might affect radar performance. (See the
left-hand figure in Figure 2-5).
The STC reduces the amplification of
echoes at short ranges (where clutter is the
greatest) and progressively increases
amplification as the range increases, so
amplification will be normal at those ranges
where there is no sea clutter. The control is
effective up to about 4 miles.
STC can be adjusted automatically or
manually. If you select AUTO, the STC
automatically adjusted. The range of STC
adjustment is from 1 to 3; 3 is the highest.
For manual adjustment, first adjust the gain
and then transmit on short range. The
range of STC adjustment is from 00 to 50.
Adjust the STC level such that the clutter is
broken up into small dots, and small targets
become distinguishable. If the setting 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 display.
In most cases adjust so clutter has
disappeared to leeward, but a little is still
visible windward.
If there is no clutter visible on the display,
turn off the circuit.
Sea clutter at
display center
STC adjusted;
sea clutter suppressed.
Figure 2-5 Effect of STC
How to adjust A.C RAIN and FTC
(suppressing rain clutter)
The vertical beamwidth of the antenna is
designed to see surface targets even when
the ship is rolling. However, by this design
the unit will also detect rain clutter (rain,
snow, hail, etc.) in the same manner as
normal targets. Figure 2-6 shows the
appearance of rain clutter on the display.
Adjusting A.C RAIN
When rain clutter masks echoes over a
wide range, raise the A.C RAIN slightly to
distinguish targets from the clutter.
Appearance of
rain clutter
A.C RAIN adjusted;
rain clutter suppressed.
Figure 2-6 Effect of A.C RAIN