Raymarine RL70C, Owner'S Handbook Manual

Page: 74 / 218

60 HSB Series LCD Display
Rain Clutter Control, using RAIN and FTC
The radar can see echoes from rain or snow. Returns from storm areas and rain
squalls consist of countless small echoes that continuously change size,
intensity, and position. These returns sometimes appear as large hazy areas,
depending on the intensity of the rainfall or snow in the storm cell.
The
RAIN
and
FTC
controls are used to reduce this clutter, so that targets masked
by the clutter can be seen on the radar picture.
• The
RAIN
control is used to reduce large clutter masses around your vessel
caused by rain or snow.
• The
FTC
(Fast Time Constant) control is used to reduce rain clutter at a
distance from your vessel, such as that shown below.
D3967-1
When the
FTC
control is turned up, only the leading edge of large (rain clutter)
echoes is displayed, while the effect on smaller (ship) echoes is only slight. This
means that you can also use the control on shorter ranges to distinguish between
two very close echoes on the same bearing, which may otherwise merge and
appear as one echo.
When the
FTC
control is turned up, the receiver is less sensitive, and there is a
reduction of background noise and fill-in returns from land and large targets.
You should therefore turn the control down when its use is not required. Since
storm cells are usually visible for long distances due to their extreme altitude,
you may wish to leave them displayed so that you can observe the location of
bad weather.
If you turn the
RAIN
or
FTC
control Off (equivalent to setting the level to 0%), the
actual setting is stored, and restored when you turn the control on again.
Note:
RAIN
and
FTC
are reset to Off at power-on.
Adjusting Gain
Sea Clutter and
Rain Clutter
RAIN
O
F
F
FTC
O
F
F