6. RADAR
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Virtual image
A large target near your ship can show at two positions on the screen. One of the po-
sitions is the true echo reflected by the target. The other position is a false echo which
is caused by the "mirror effect" of a large object on or near your ship. See the figure
shown below for an example of this type of false echo. If your ship gets near a large
metal bridge, for example, a false echo appears on the screen. The echo disappears
after move some distance from the bridge.
Sector blanking
Funnels, stacks, masts, or derricks in the path of the antenna stop the radar beam. If
the angle opposite the antenna is more than one or two degrees, a sector or shadow
sector appears on the screen. Targets are not displayed within the sector.
Target ship
Route for direct reflection
Own ship
True
echo
False
echo
Bridge
Route for
indirect reflection
Mirror image
of target ship
Radar position
Large ship
Wharf and its echo
Sector blanking
occurs because
wharf is hidden
behind ship.
Radar position
Wharf and its echo
Sector blanking occurs
because obstruction
(like mast) is in path of
radar beam.
Size of blanking sector depends
on size of obstruction and range.
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