User Manual

A. Ghost echoes

It sometimes happens that one large object near the ship appears at two different bearings.

One is the actual echo and other is a ghost echo generated as the wave is re-reflected from the

ship's own smokestack or mast. The former appears at the correct distance and bearing on the

screen and the latter appears behind the smokestack or mast. This type of false echo is also gen-

erated by re-reflection of waves from bridges and quay walls other than the ship itself.

Fig.2-5 False echoes of radar (Ghost echoes)

B. Multiple echoes

If there is a large vertical reflecting plane near the ship as in the case when your ship passes

alongside a large ship, the wave is repeatedly reflected back and forth between your ship and the

other object. For this reason, two to four images appear on the screen at equal intervals in the same

bearing. A false echo that is generated by such multiple reflections is called multiple echoes. In this

case, an image appearing at the nearest position is the real echo. Multiple echoes disappear as the

ship moves away from the reflecting object or its bearing changes. Therefore, it is not difficult to

determine the correct image.

Fig.2-6 False echoes of radar (Multiple echoes)

C. False echoes caused by side lobe

The radiant beam emitted from an antenna contains side lobes in directions other than that of

the main beam. Since the side lobe level is low, it in no way affects distant targets. However, if

there is a strong reflecting target near the ship, it sometimes appears as a circular-arc false echo on

the screen.

When located near large targets such as land, the

ship's mast, etc. sometimes appears as a false echo

of circular-arc shape.

CAUTION

Target

Direct reflection

path

Secondary

reflection path

Mast etc.

Real echo

Ghost echo

Direction of ghost echo

Real echo

Multiple

echoes