Instruction Manual

4 RA51/52/53/54/55 INSTRUCTION MANUAL – 05

antenna on the second bounce. The actual echo appears at the correct distance and bearing on the

screen. The ghost echo appears somewhere behind your boat. This type of false echo is also gen-

erated by re-reflection of waves from bridges, quay walls or building along shore.

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

B. Multiple echoes

If there is a large vertical reflecting surface near your boat, as in the case when you pass alongside

a large ship, radar signals are repeatedly bounced back and forth between your boat and the other

object. Two to four images appear on the screen at equal intervals in the same bearing. This is

called a multiple echo. The image appearing closest to you is the real echo. Multiple echoes will

disappear as you move away from the reflecting object or its bearing changes.

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

C. False echoes caused by side lobe

An antenna's side lobe emissions are low power, and will not register distant targets. However, if

there is a strong reflecting target near your boat, it sometimes may appear as a circular-arc false

echo on the screen.

When near large targets or land, your boat's mast

may sometimes appear as a circular-arc shaped

false echo.

CAUTION

Target

Direct reflection

path

Secondary

reflection path

Mast etc.

Real echo

Ghost echo

Direction of ghost echo

Real echo

Multiple

echoes