Furuno FAR-21 7-BB Series, Operator'S Manual

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1. RADAR OPERATION
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1.18.2 Adjusting A/C RAIN
The vertical beam width of the antenna is designed to see surface targets even
when the ship is rolling. However, by this design the unit will also detect rain
clutter (rain, snow, or hail) in the same manner as normal targets.
The A/C RAIN control adjusts the receiver sensitivity as the A/C SEA control
does but rather in a longer time period (longer range). The higher the setting the
greater the anti-clutter effect. When echoes from precipitation mask solid targets,
adjust the A/C RAIN control to split up these unwanted echoes into a speckled
pattern, making recognition of solid targets easier.
(a) True target trails
(No smearing of
stationary targets)
(b) Relative target trails
Targets moving relative
to own ship
Appearance of rain clutter
Keyboard
Adjust the A/C RAIN with the [A/C RAIN] control.
Trackball
1. Roll the trackball to place the cursor in the A/C RAIN level indicator at the top
right side of the display.
RAIN
Place arrow inside window
to adjust A/C RAIN.
Level bar
(Shows A/C RAIN level.)
30
A/C RAIN level indicator
2. While observing the A/C RAIN level indicator, roll the wheel downward to
increase the A/C RAIN or upward to decrease it. 100 levels (0-100) are
available.