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AUTO 1 2 3
MAN
AUTO 1 2 3
MAN
GAIN
STC
A/C RAIN 00
A/C AUTO OFF ON
12
ECHO KEY
TO EXIT
Current
level
Item selected
for adjustment
Figure 1-4 Display for adjustment of
GAIN, STC, A/C RAIN
2) Press the cursor pad to select item to ad-
just. Current selection is circumscribed
by dashed rectangle.
3) Press the [ENT] key.
3) Press the cursor pad to set level.
4) Press the [ECHO] key to finish.
The A/C AUTO function automatically sup-
presses sea clutter as well as rain clutter.
Note: With the radar having a linear amplifier,
radar picture may not be adjusted properly
through the menu.
How to adjust the gain (sensitivity)
The gain works in precisely the same man-
ner as the volume control of a broadcast re-
ceiver, amplifying the signals received.
You can adjust the gain automatically or
manually. For manual adjustment, adjust the
sensitivity on the highest range—the back-
ground noise is clearer on that range. The
proper setting is such that the background
noise is just visible on the screen. If you set
up for too little gain, weak echoes may be
missed. On the contrary excessive gain
yields too much background noise; strong
targets may be missed because of the poor
contrast between desired echoes and the
background noise on the display.
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 scan-
ner above the water, the further the clutter
will extend. Sea clutter appears on the dis-
play as many small echoes which might af-
fect radar performance. (See the left-hand
figure in Figure 1-5).
The STC reduces the amplification of ech-
oes at short ranges (where clutter is the great-
est) and progressively increases
amplification as the range increases, so am-
plification 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 manu-
ally. For manual adjustment, first adjust the
gain and then transmit on short range. Ad-
just 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 disap-
peared 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 1-5 Effect of STC