Raymarine Marine GPS System User Manual page 111

RayTech Navigator User's Guide
Interference Rejection
Mutual radar interference is likely when two or more radar-equipped
vessels are operating within range of each other. This usually appears
as a series of small dots moving to and from the display center in a
straight line or a long, sweeping curve (Figure 5-7). This type of
interference is most noticeable at long ranges.
The Pathfinder PLUS Radar includes a mechanism that automatically
reduces such interference. This mechanism is normally left switched
on. However, if you wish to detect the presence of other radars in the
vicinity, you can turn off the interference rejection.
Target Expansion
You can make targets easier to see by expanding them. The scanner type
determines the range at which target expansion is available. Target
expansion overrides the normal pulse length, thereby increasing the size
of the target seen on the screen. However, this is at the expense of range
resolution.
5-20
Figure 5-7. Radar Interference Rejection Display