56
HSB Series LCD Display
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
True echo
Passing
ship
True echo
False echo
D1641-2
Mast
or funnel
Indirect (false) echoes
Multiple Echoes
Multiple echoes 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 target’s echo on the same bearing (as shown below). This is not
very common.
D1642-1
True echo
Multiple echoes
MULTIPLE ECHOES
Blind Sectors or Shadow Effect
Funnels and masts, when located near the antenna array, 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 which extend behind the obstruction. This should be
avoided by careful selection of the scanner site prior to installation (see
Chapter 8
).
Identifying False
Echo Returns
Содержание RC520
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