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2. RADAR, CHART RADAR OPERATION
2-4
2.5.1 How to reduce sea clutter automatically
Auto A/C SEA allows for fine-tuning of the A/C SEA circuit, within ±20 dB. Lower the
auto A/C SEA level because the average value of the original input echo is low in ar-
eas where there are no see surface reflections. For example, when the ship is along-
side a quay and the radar picture shows echoes from both land and sea, you can
observe the size of echoes because the STC curve is different depending size of ech-
oes.
To get automatic adjustment of sea clutter, do one of the following:
Control Unit: Push the A/C SEA control to display [AU-
TO] on the SEA mode indication on the Status bar.
Trackball module: Click the SEA mode indication on
the Status bar to display [AUTO].
2.5.2 How to reduce sea clutter manually
The A/C SEA control reduces the ampli-
fication of echoes at short ranges (where
clutter is the greatest) and progressively
increases amplification as the range in-
creases, so amplification will be normal
at those ranges where there is no sea
clutter.
The proper setting of the A/C SEA
should be 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 the setting is too high, both sea clutter and targets will disappear from the display. In
most cases adjust the control until clutter has disappeared to leeward, but a little is still
visible windward.
Be careful not to remove all sea clutter, because you may erase weak echoes. Fur-
ther, the possibility of losing weak echoes is greater when you use both A/C SEA and
A/C RAIN to reduce clutter.
To reduce sea clutter manually, do one of the following:
Control Unit: Push the A/C SEA control to display [MAN] on the SEA mode indication
on the Status bar. Rotate the A/C SEA control to adjust the sea clutter.
Trackball module: Click the SEA mode indication on the Status bar to display [MAN].
For coarse adjustment, put the cursor within the slider bar area then push the left but-
ton. For fine adjustment, put the cursor at the end of the slider bar then roll the trackball
while pushing and holding down the left button. Release the button to finish.
SEA mode indication
Sea clutter at
screen center
A/C SEA adjusted; sea
clutter suppressed