Suppressing Rain Clutter; Measuring The Range - Furuno 1623 Operator's Manual

Manual A/C SEA adjustment
While observing the screen and the A/C
SEA tuning bar, press ◄ or ► to set the
A/C SEA. The setting range is 0-100.
4. Press the [MENU/ESC] key to finish.

1.9 Suppressing Rain Clutter

The vertical beamwidth of the antenna is
designed to see surface targets even when
the ship is rolling. However, by this design the
antenna will also pick up rain clutter (rain,
snow, or hail) in the same manner as normal
targets. The illustration below shows the
appearance of rain clutter on the display.
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.
1. Press the [GAIN] key consecutively until
the display shown below appears.
[GAIN] : GAIN MENU
[MENU/ESC] : Exit.
A/C RAIN adjustment window
2. While observing the screen and the A/C
RAIN tuning bar, press ◄ or ► to adjust
the A/C RAIN. The setting range is 0-100.
3. Press the [MENU/ESC] key to finish.
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Rain clutter at screen center
A/C RAIN
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1.10 Measuring the Range

The bearing to a target can be measured by
the range rings, by the cursor and by the
VRM (Variable Range Marker).
Measuring range by the cursor
Operate the cursor pad to place the cursor on
the inside edge of the target. Read the range
to the cursor at the bottom right corner of the
display.
Measuring range by the range rings
Count the number of rings between the
center of the display and the target. Check
the range ring interval and judge the distance
of the echo from the inner edge of the nearest
ring.
Note: The range rings can be turned on or off
with RINGS on page 1 of the System menu.
Measuring range by the VRM
1. Press the [MARK] key to show the Mark
menu.
MARK MENU
[GAIN] : EBL
[ALARM] : VRM
[MARK] : TLL OUTPUT
Mark menu
2. Press the [ALARM] key to display the
VRM, which is a dashed ring to
distinguish it from the range rings.
3. Operate the cursor pad to place the VRM
on the inside edge of the target.
4. Check the VRM readout at the bottom left
corner on the screen to find the range to
the target.
To anchor the VRM on the screen, press the
[MENU/ESC] key. To erase the VRM, press
the [ALARM] key twice with the MARK MENU
displayed.
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1. OPERATION