Raymarine Marine GPS System manual Multiple Echoes, Blind Sectors or Shadow Effect

RayTech Navigator User’s Guide

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.

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