User's Manual

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JMA-9100 Instruction Manual > 6.TRUE AND FALSE ECHOES ON DISPLAY > 6.4 FALSE ECHOES

c. False Echo by Secondary Reflection

When a target exists near own ship, two echoes from the single target may appear

on the radar display.

One of those echoes is the direct echo return from the target and the other is the

secondary reflection return from a mast or funnel that stands in the same direction

as shown in Fig 6-7.

Fig 6-7: False echo by secondary reflection

d. False Echo by Multiple Reflection

When there is a large structure or ship with a high vertical surface near own ship

as shown in Fig 6-8, multiple refection returns may appear on the radar display.

These echoes appear in the same intervals, of which the nearest echo is the true

echo of the target.

Fig 6-8: False echo by mutiple reflection

e. Second Time Echoes

The maximum radar detection range depends upon the height of the scanner and

the height of a target as described in the Section 6.1 "RADAR WAVE WITH THE

HORIZON". If a so-called “duct” occurs on the sea surface due to a certain

weather condition, however, the radar beam may propagate to a abnormally long

distance, at which a target may be detected by the radar.

Radar

scanner

Funnel

Direct microwave

Secondary reflection

of microwave

Actual target

False echo from funnel