Furuno FCR-2107 series, Operator'S Manual

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2. Radar Operation
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2.6 Choosing the Range Scale
The selected range scale, range ring interval and pulse length are shown at the upper left corner on the screen. When
a target of interest comes closer, reduce the range scale so that it appears in 50-90% of the display radius.
From the control unit w/keyboard
Use the RANGE key to select range desired. Hit the "+" part of the key to raise the range; the "-" part to lower the
range.
By trackball
1.
Use the trackball to select the RANGE box at the top left corner of the screen. The guidance area shows
"RANGE - / OK / RANGE +".
2. Push the left button to lower the range; the right button to raise the range. You can also select the range by
spinning the scrollwheel then pushing it.
2.7 Adjusting the Sensitivity
The gain control adjusts the sensitivity of the receiver. The proper setting is such that the background noise is just
visible on the screen. If you set up for too little sensitivity, weak echoes may be missed. On the other hand excessive
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.
Adjust the gain so background noise is just visible on the screen.
From the control unit w/keyboard
While monitoring the radar image, operate the GAIN control to adjust the sensitivity.
By trackball
1. Use the trackball to place the arrow on the gain level indicator at the top of the screen.
Gain level
Put arrow inside box
to adjust gain.
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Gain
2. Spin the scrollwheel downward to increase the gain or upward to decrease it. 100 levels (0-100) are available.
2.8 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 antenna above the water, the further the clutter will extend. When sea clutter masks the
picture, suppress it with the A/C SEA control, either manually or automatically.
When both sea clutter and rain clutter are reduced, the sensitivity is decreased more than when only one is adjusted.
For that reason adjust them carefully.
The echo average is useful for reducing reflections from the sea surface. However, high-speed targets are harder to
detect than stationary ones when the echo average is active.