Installation Instructions

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 surprisingly 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 misunderstood 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, how-

ever, it appears as spiral or radial patterns.

The RA40C/41C/42C radar has a function to elimi-

nate interference. Use of this function helps you minimize

interference.

2.3 Terms Specific to Radar

HM (Heading Marker)

This is a line-shaped marker used to indi-

cate the advancing direction of your ship.

North Mark

This marker indicates the north direction.

It is a short line approximately 1/6 of the

screen size.

Radar inrterference

Fig.2-8 Radar interfer-

ence

0.75

0.25

HM(Heading Marker)

North Mark

Fig.2-9 Heading Marker and

North Mark