Adjusting The A/C Rain Control (Reducing Rain Clutter) - Furuno Marine Radar Operator's Manual

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
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.
A/C SEA control adjusted;
sea clutter suppressed.
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
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 navigating in
confined waters. However, with the cir-
cuit activated the receiver is less sensi-
tive. 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 AUTO] key. "A/C AUTO" ap-
pears at the bottom left-hand corner of the dis-
play when the A/C AUTO circuit is on. You can
fine tune by adjusting the [A/C SEA], [A/C
RAIN] and [GAIN] controls.
A/C RAIN control adjusted;
rain clutter suppressed.
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