Furuno FR-1710, Operator'S Manual

Page: 26 / 78

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1.14 Adjusting the Sensitivity
The GAIN control adjusts the sensitivity of
the receiver. It works in precisely the same
manner as the volume control of a broadcast
receiver, amplifying the signals received.
The proper setting is such that the back-
ground noise is just visible on the screen. If
you set up for too little sensitivity, weak ech-
oes may be missed. On the other hand ex-
cessive sensitivity 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.
To adjust receiver sensitivity, transmit on long
range, and adjust the GAIN
control so back-
ground noise is just visible on the screen. The
current gain setting is shown by the “GAIN
bar” at the top right-hand corner of the screen.
1.15 Suppressing Sea Clutter
Echoes from waves cover the central part of
the display with random signals known as sea
clutter. The higher the waves, and the higher
the scanner above the water, the further the
clutter will extend. When sea clutter masks
the picture, suppress it by the A/C SEA con-
trol, rotate for manual adjustment, push for
automatic adjustment.
Manual adjustment by the A/C SEA
control
The A/C SEA control reduces the amplifica-
tion of echoes at short ranges (where clutter
is the greatest) and progressively increases
amplification as the range increases, so am-
plification will be normal at those ranges
where there is no sea clutter.
The proper setting of the A/C SEA control
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
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 the
control until clutter has disappeared to lee-
ward, but a little is still visible windward.
1. Confirm that the sensitivity is properly
adjusted, and then transmit on short
range.
2. Adjust the A/C SEA control so small tar-
gets are distinguishable but some clutter
remains on the display.
A/C SEA control
off A/C SEA control
adjusted
Figure 1-11 How to adjust
the A/C SEA control
Automatic adjustment by the A/C
AUTO control
The A/C AUTO control automatically sup-
presses sea clutter as well as rain clutter.
Push the A/C SEA control to turn on the au-
tomatic A/C circuit. A/C AUTO appears at the
bottom left corner when the A/C AUTO cir-
cuit is on. Fine adjustment of the circuit can
be done with the A/C RAIN and A/C SEA con-
trols.
CAUTION
Turn off the A/C AUTO feature when its use
is not required; it can erase weak target
echoes.