User Manual

Fig.2-7 False echoes of radar (Caused by side lobe)

D. Distant false echoes caused by duct phenomenon

Depending on meteorological conditions, duct phenomenon sometimes occurs in temperature

inverting layers of air. In such a case, the wave propagates erratically reaching a location sur-

prisingly far away from the ship. In this case, a target present at a distant location more than the

radar's maximum distance range appears on the screen presenting a false echo that can be mis-

understood to be present nearer than the actual position. This phenomenon is attributed to the fact

that since echo from the distant target arrives late, it gets out of the pulse repetition frequency and

is displayed on the screen as an echo in the next frequency. If the target distance changes as you

switch over the distance range, you can determine that it is a false echo.

Radar interference

If a radar operating in the same frequency exists near your ship,

interference noise may appear on the screen that is caused by

transmitted waves from that radar. This interference appears in

various ways. In most cases, however, it appears as spiral or radial

patterns.

The RA53/54 radar has a function to eliminate interference. Use

of this function helps you minimize interference.

Fig.2-8 Radar interference

Antenna

Main beam

Side lobes

Real echo

False sidelobe

echoes

Radar inrterference