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(1) Precautions to be observed when installing the scanner unit on a power boat
The bow of a power boat is kept in a raised position when it is running at a high
speed. Consequently, if the radar's scanner unit is installed horizontally when the
boat is stopped, the following conditions will occur if the trim (elevation angle of the
ship's bow at run time) exceeds 1/2 of the vertical beam width (θ):
• On the front side, the water surface lies outside the beam, weakening the radio
wave that is incident to the target on the water surface. Consequently, the
echo generated by this target is will hardly be visible on the radar screen.
Conversely, on the rear side:
• Since the radio wave that is incident to the water surface is stronger, strong sea
clutter will develop. For vessels on which the trim is 1/2 or greater than the ver-
tical beam width (θ), it is recommended that the scanner unit be installed in
such an orientation that it is tilted forwards.
Beam width θ
[When the ship is stopped or running at a slow speed]
Beam width θ
[High speed run: the lower part of the beam is almost horizontal.]
Horizontal line
Horizontal line
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Radar scanner unit
Radar scanner unit
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