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

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.
Rain clutter at screen center
1. Press the [GAIN] key once or twice to
show the display below.
A/C RAIN
[GAIN] : GAIN MENU
[MENU/ESC] : EXIT
A/C RAIN adjustment window
2. While observing the screen and the tuning
bar, use ◄ or ► to adjust the A/C RAIN.
The setting range is 0-100.
3. Press the [MENU/ESC] key to finish.

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).
65
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 VRM
1. Press the [MARK] key to show the Mark
menu.
MARK MENU
[GAIN] : EBL
[ALARM] : VRM
MARK] : OUTPUT TLL
Mark menu
2. Press the [ALARM] key to display the
VRM, which is a dashed line to
distinguish it from the heading line.
"VRM," displayed in reverse video,
appears at the bottom left corner.
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 fix the VRM on the screen, press the
[MENU/ESC] key. To erase the VRM, press
the [ALARM] key.
6.0
nm
2.0
VRM
VRM
VRM 2.91
nm
range
How to measure the range with the
VRM and cursor
6
Target
Cursor
Range, bearing
and time-to-go
RNG 2.91nm
to cursor
BRG 45.62°
TTG: 02H21M
location