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Adjusting the A/C SEA control
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 control is set too low, targets will be hid-
den in the clutter, while if it is set 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.
1. Confirm that the sensitivity is properly ad-
justed, and then transmit on short range.
2. Adjust the [A/C SEA] control so small tar-
gets are distinguishable but some clutter re-
mains on the display.
Sea clutter at
display center
A/C SEA control adjusted;
sea clutter suppressed.
Figure 2-4 How to adjust the A/C SEA control
Tip for adjusting the A/C SEA
A common mistake is to over-adjust the circuit
so all the clutter is removed. As an example set
up for maximum A/C SEA. You will see how
the center of the display becomes dark. This
dark zone can be dangerous (targets may be
missed), especially if the sensitivity is not prop-
erly adjusted. Always leave a little clutter vis-
ible on the display to be sure weak echoes will
not be suppressed. If there is no clutter visible
on the display, turn off the circuit.
Turn off the A/C SEA control when
its use is not required; the control
can erase weak targets.
CAUTION
2.10 Adjusting the A/C RAIN
Control
(reducing rain clutter)
The vertical beamwidth of the antenna is de-
signed 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 2-5
shows the appearance of rain clutter on the dis-
play.
Adjusting A/C RAIN
When rain clutter masks echoes, adjust the [A/
C RAIN] control. This control splits up these
unwanted echoes into a speckled pattern, mak-
ing recognition of solid targets easier.
Appearance of
rain clutter
A/C RAIN control adjusted;
rain clutter suppressed.
Figure 2-5 Effect of A/C RAIN
Note: In addition to reducing clutter, the [A/C
RAIN] control can be used in fine
weather to clarify the picture when navi
gating in confined waters. However,
with the circuit activated the receiver is
less sensitive. Therefore, turn off the
circuit when its function is not required.
Automatic adjustments of A/C SEA
and A/C RAIN
Push the [A/C SEA (A/C AUTO)] control. “A/
C AUTO” appears at the bottom left-hand cor-
ner of the display when the A/C AUTO circuit
is on. You can fine tune by adjusting the [A/C
SEA], [A/C RAIN] and [GAIN] controls.