JRC JMA-9172-SA, Instruction Manual

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JMA-9172-SA Instruction Manual
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6.TRUE AND FALSE ECHOES ON DISPLAY
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6.4 FALSE ECHOES
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6
6.4
FALSE ECHOES
The radar observer may be embarrassed with some echoes that do not exist
actually. These false echoes appear by the following causes that are well known:
a. Shadow
When the radar scanner is installed near a funnel or mast, the echo of a target that
exists in the direction of the funnel or mast cannot appear on the radar display
because the radar beam is reflected on the funnel or mast. Whether there are some
false echoes due to shadows can be checked monitoring the sea clutter returns, in
which there may be a part of weak or no returns.
Such shadows appear always in the same directions, which the operator should
have in mind in radar operation.
b.
Side Lobe Effect
A broken-line circular arc may appear at the same range as the main lobe of the
radar beam on the radar display. This type of false echo can easily be
discriminated when a target echo appears isolated. (see Fig 6-6)
Fig 6-6: False echo
HL