Raymarine Marine GPS System manual Rain Clutter Control, Radar Rain Clutter Display

RayTech Navigator User’s Guide

Rain Clutter Control

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 (Figure 5-6). 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.

Figure 5-6. Radar Rain Clutter Display

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.

5-16