Raymarine Marine GPS System - Manual (Page 103)

RayTech Navigator User’s Guide
5-12
Multiple Echoes
Multiple echoes (Figure 5-4) appear if there is a large target with a
wide vertical surface at a comparatively short range. The transmitted
signal will be reflected back and forth between the target and your
own ship. Multiple echoes therefore appear beyond the true targets
echo on the same bearing, as shown in the figure below. This is not
very common.
Figure 5-4. Radar Multiple Echo Affects
Blind Sectors or Shadow Effect
Funnels and masts located near the antenna, may cause shadows.
In shadow areas beyond the obstruction there will be a reduction of
the beam intensity, although not necessarily a complete cut-off.
However, there will be a blind sector if the subtended angle is more
than a few degrees. There may also be multiple echoes that extend
behind the obstruction. This should be avoided by careful selection
of the scanner site prior to installation.