Furuno 1830 - A;C Sea Control Adjustment

AdjustintJ the A/C SHA Control
Kchoes from waves oan be troublesorae, covering the central part of tJie
display with random signals known as "sea dutter." The higher the waves,
and the lower the scanner above the water, the further the dutter wiU
exlend. bea dutter appears on the screen as a large number of small
echoes which might affeet radar performance (see Fig.25A). The action of
the A/C SHA is to reduce the amplification of echoes at short ranges (where
dutter is the greatest) and progressively inerease amphfication as the range
inereases, so tiiat ampiifiuatioii will De normal al ihose ranges where sea
dutter is not experienced. The control is only effeetive up to a maximum of
about 4 miles.
The proper setting of the A/C SHA is such that the dutter is broken up
into small dots, and small targets become distinguishable- If the control is
not sufficiently advanced. other targets will be bidden in the dutter, while
if It is set loo nigti, sea clutter and targets will both disappear from the
screen. As a general rule of thu mb. turn the control clockwise until dutter
has di.sappeared to leeward. but a ittle is still visible windward. Fig.25
illustrates how to adjust the A/C SKA control.
(A) Sea Glutter. A/C SHA control "OFH" (H) A/C SEA properly adjusleri
Fig.25 Adjusting the A/C SEA
A common mistake is too over adjust the control 90 that all the olutter is
removed. By rotating the control fully clockwise you will see how dangerous
this may be; a dark zone is created near the center of the screen. This
dark zone can be dangerous (targets may be missed), especially if the gain
has not been properly adjusied. Aiways leave a Jittle clutter visible on the
screen, this ensures weak echoes will not be suppressed. If no dutter is
visible on the screen, leave the control in the fully counterclockwise
position.
As mentioned before (in the procedure to set up the GAIN and A/C SEA
when the radar is first initiahzed after installation), the GAIN is normally
set to the point where there is a trace of noise speckles showing on the
screen on the 12 or 24 mile range, and then the A/C SEA is adjusted on the
0.25 mile range scale so that dose-in targets in a harbor situation are
oloarly seeo- This aqualiaøs thø GAIN and A/C SKA charactcristics for all
ranges, short and long.
In moderate conditions on the open sea, where there are no definite targets
to be seen on the shorter ranges. you should still adjust the GAIN on the
12 or 24 mile range for some noise speckles on the CRT, and then go down
to the 0.5 or 0.75 mile range to adjust the A/C SEA until a bil of sea
clutter is uD.servucl ulose lu the boat.