Furuno FR-2105 Operator's Manual page 34

Automatic anti-clutter control
The easiest way to suppress the surface clutter
is to use the automatic control. Press the A/C
AUTO key. Use of a function key is also a
good method for reducing sea clutter. For this
purpose, presetting is required. Consult a
FURUNO representative.
CAUTION
The auto A/C function can erase weak target echoes.
Manual anti-clutter control
From the fully counterclockwise position, slowly turn the A/C SEA control clockwise. For
optimum target detection, you should leave speckles of the surface return slightly visible.
The anti-clutter sea control is often referred to as STC (Sensitivity Time Control) which
decreases the amplification of the receiver immediately after a radar pulse is transmitted, and
progressively increases the sensitivity as the range increases.
A common mistake is to over-adjust the A/C SEA control so that the surface clutter is
completely removed. By rotating the control fully clockwise, you will see how dangerous this
can be; a dark zone is created near the center of the screen and close-in targets can be lost.
This dark zone is even more dangerous if the gain has not been properly adjusted. Always
leave a little surface clutter visible on the screen. If no surface clutter is observed (on a very
calm water), set the control at the fully counterclockwise position.
HL PANEL
OFF BRILL
1 2
OFF
VECTOR
CENTER
4 5
CHART
EBL
ALIGN
7 8
TARGET CU, TM
TRAILS RESET
CANCEL 0
-1.17-
MODE
AUDIO RADAR PLOT
OFF
MENU MENU
3
LOST
TARGET
6
AC
MARK
TARGET
9
DATA
A/C
AUTO TARGET
CANCEL
ENTER
A/C AUTO key
NAV
MENU