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Indirect echoes
There are several types of indirect echoes or ghost images. These sometimes have the
appearance of true echoes, but in general they are intermittent and poorly defined.
False echo
Passing
ship
Multiple echoes
Multiple echoes are not very common but can occur 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 boat, resulting in multiple
echoes, displayed beyond the range of the true target echo, but on the same bearing.
Blind sectors or shadow effect
Obstructions such as funnels and masts near the radar antenna may obstruct the radar
beam and cause radar shadows or 'blind sectors'. If the obstruction is relatively
narrow, there will be a reduction of the beam intensity, though not necessarily a
complete cut-off. However, for wider obstructions there may be a total loss of signal in
the shadow area. There may also be multiple echoes which extend beyond the
obstruction. Blind sector effects can normally be minimized by careful selection of the
scanner site prior to installation.
True echo
Mast
or funnel
D1642-1
Multiple echoes
True echo
False echo
True echo
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