Gain Mode - Raymarine RayTech RNS 5.0 User Manual

Chapter 7: Using radar 49
With the FTC function set high, the receiver is made less sensitive, and there is a
reduction of background noise and fill-in returns from land and large targets. You
should therefore set the control to low (or Off) when its use is not required.
Rain mode
Your radar can see echoes from rain and snow. These returns from storm areas and rain
squalls consist of countless small echoes that continuously change size, intensity and
position.
You should use the rain function to reduce large clutter masses from these returns
around your boat.
Sea mode
The sea clutter control reduces the gain level in the area near your boat, extending for
3 to 5 nm depending on the wave and sea conditions. This reduces sea echoes to
intermittent small dots, while small targets remain visible. Gain levels further from
your boat are unchanged.
The sea clutter control can be set to Auto-Harbor (default), Auto-Offshore, or manual
mode. In Auto-Off-shore mode, the radar optimizes its settings to account for the
effects of sea clutter. In harbors and close proximity to land, different auto settings may
be necessary to account for land clutter. To avoid losing small targets, set the sea
clutter control to Auto-Harbor mode. If you set the sea control to manual mode, be sure
you adjust the settings to ensure that all close small targets are visible.

Gain mode

The gain control adjusts the level of the display of signals received from the scanner;
and is the equivalent to the volume control on a radio. The gain control can be set in
either Auto or Manual mode.
In auto mode, the radar self optimizes its settings. In harbors or close proximity to land,
different auto settings may be necessary to compensate for the effects of land clutter.
In manual mode, you must adjust the settings to ensure that all close small targets are
visible, and you should check it every time you change the range scale. On long range
settings, the gain should be set to give a slight speckle in the background of the radar
picture. On shorter ranges, you may want to reduce the gain slightly to reduce the
speckle and improve target definition. Do not set the gain too low, or you may miss
small or weak targets. The gain mode and its associated settings are retained each
time you turn the radar off.
Tune
You can use the tune control to fine-tune the receiver in the radar's scanner to yield
maximum target returns on the display.