Adjustingthe Gain Control.2-6 - Furuno 1751 Operator's Manual

2. OPERATIONAL OVERVIEW
Basic Operation
Adjusting the GAIN control
The
GAIN
Control adjusts the sensitiv!ty of the receiver, and thus the strength of echoes as
they appear on the screen. Adjust it so the speckled noise background is just visible on the
display.
To become acquainted with the way the control works, try rotating it between its fully
counterclockwise and clockwise positions as you observe the display. As you slowly turn the
control clockwise you should be able to see the speckled background appear when the
position of the control is between 2 and 3 o'clock.
To properly set the gain, use the highest range— the background noise is clearer on this
range. If you set up for too little gain, weak echoes may be missed. If you turn the control too
far clockwise, yielding too much background noise, strong targets may be missed because of
the poor contrast between desired echoes and the background noise on the display. Figure
2-5 illustrates examples of gain settings which are too high, proper, and too low.
(A) Too high (B) Proper (C) Too low
Figure 2-5 Adjusting the GAIN Control
Tips on adjusting GAIN
1) In certain circumstances it may be useful to reduce the gain slightly to improve range
resolution, clear up the picture, or reduce dutter caused by rain or snow.
2) Range resolution is a measure of the capability of a radar to display as separate pips the
echoes received from two targets which are on the same bearing, and are close together
radially. With reduction in the gain setting, the echoes may be made to appear as separate
pips on the display.
3) When sailing or cruising in crowded regions a slight reduction in gain often helps to clear
up the picture. This should be done carefully, otherwise weak targets may be missed.
4) Echoes from ships inside a squall or storm may be obscured if the gain is at its normal
setting, since the dutter may have masked, but not completely, echoes from the targets.
In all cases, return the gain to its original position after any temporcuy reduction is no longer
required.
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