Operator`s manual

Chapter 3-6 Radar menu
alert for objects in these blind sectors.
 The DX45 and DX60 scanners have an advanced blind sector func-
tion where up to two sectors can be defined and cover a total of
90°. The sectors will be clearly marked on the screen and in order
to eliminate ghost echoes (false reflecting targets), there will be no
radar signals transmitted into the defined sector(s).
3.1.9 Side lobes
Echoes on the radar screen are not always the direct returns to the
radar antenna. There are many types of false echoes that can appear
on the display if certain conditions occur. The sections that follow,
briefly describe the echo patterns that may be produced by these
false echoes and their likely cause. It should be noted that the radar
operator, through observation, practice, and experience usually can
detect these conditions very quickly.
A very small part of the RF (Radio Frequency) energy from each
transmitted pulse is radiated outside the radar’s narrow beam, pro-
ducing side lobe patterns. Side lobes normally have no effect from
distant or small surface objects, but the echo from a large object at
short range may produce an arc pattern on the radar screen similar
to a range ring, or appear as a series of echoes forming a broken arc.
Side lobe echoes normally occur at a range below 3 miles and usu-
ally can be reduced through careful reduction of the Gain or proper
adjustment of the Sea clutter control.
3.1.10 Radar interference
Whenever two or more radar equipped vessels are operating within
reception range of each other, mutual interference is likely when the
radars are operating near the same frequencies. This interference
usually appears on the screen as a series of small dots. The interfer-
ence seems to move from the PPI center (center of radar screen),
sometimes in a straight line, but more often in a long, sweeping
curve. This type of interference is more noticeable on longer range
scales. This does not, as a rule, impair the effectiveness of the radar
as a navigational aid. Since the interference can be completely elimi-
nated by turning IR “ON” in the function menu. The IR feature is
normally left “on”.