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Nobeltec InSight Radar (IR2)
Operations Manual
False Echoes
False echoes may appear according to surrounding circumstances. Examples of
false echoes and causes of these echoes are described below.
False echoes caused by reflection
A close target may appear in two different directions. One is a real echo, while the
other is a false one produced by reflected waves from structures near the radar
antenna, such as a funnel, a mast, etc. If a large structure, like an iron bridge exists
nearby, it can also create false echoes.
False echoes caused by multiple reflection
When your boat passes near a large boat, radio waves are repeatedly reflected
between the two, causing several echoes at regular distances to appear in the
same bearing. These false echoes produced by multiple reflection are called
multiple echoes. In this case, the real target is the closest. Because multiple
echoes soon disappear when your boat moves from the reflection target or the boat
direction has changed, even if these multiple echoes are produced, the true image
is easily detected.
Shadow and dead angle
If the funnel, mast, post and other structure are located near a transceiver or if a
tall obstacle is present, a shadow is produced from the rear of these structures.
In extreme cases, no targets will appear in the shadow for a good distance. This
range is called the dead range, and the shadow can be produced entirely or
partially. Since the dead angle due to the funnel, mast, etc. is detectable during the
installation of the transceiver, it can be eliminated by changing the radar mounting
position.
False echoes caused by side lobes
The radiation beams emitted from the transceiver comprise side lobes in addition
to the main lobe. Since the side lobe energy is very low, it does not affect distant
targets. A false echo due to the sidelobes is produced from a close-in target with
strong reflections. A false echo caused by the side lobes appears as an arc. It is
eliminated by slightly reducing the gain or by changing the FTC level.
Understanding Radar
