Navman 8120 - Manual (Page 19)

NAVMAN 8120/8084 Fuel, AIS, & Radar Addendum 19
Radar problems
Radar overlay doesn’t appear on the chart
screen
a Ensure that your boat is shown on the
radar window. If it is, but the radar overlay
still isn’t shown, try zooming in on the
charted area. (The charted area may be
outside the maximum range of the radar).
b The threshold or transparency settings for
the radar overlay are not correct.
Radar shows arcs and/or shadows
Side lobe patterns often appear as an arc
or a broken arc. Shadows are blind spots.
If the radar is installed at a suitable height
and in a suitable location on your boat,
side lobe patterns and shadows caused by
obstructions such as funnels or masts will
be minimized.
If you are having problems with these,
you may need to relocate your scanner.
Consult the Installation Guide for your
radar model for advice.
Radar shows different patterns on
each sweep
Interference patterns always appear in
a different place with each sweep. They
can be randomly scattered bright dots or
dotted lines that extend from the centre
to the edge of the radar window, often
producing a spiral effect. Generally, the
stronger the interference, the wider the
interference lines.
a Use the interference rejection feature
to reduce interference patterns, and the
width of the interference lines.
Radar shows false echoes and/or
background noise
False echoes and/or background noise can
be produced if the radar sensitivity is too
high.
a Try using the Auto setting for the radar
gain mode. If this doesn’t work, or if the
radar gain mode is already set to Auto, use
the radar gain setting to reduce the radar
sensitivity.
Radar shows multiple echoes off the same
object
Multiple echoes off the same object are
most likely to occur when you are close
to a large target, and are usually only a
temporary nuisance.
Radar shows random or grouped dots
Rain clutter often appears as random dots
that can merge into badly-defined echoes
on the radar window. The random signals
are returned from rain, hail, sleet, or snow
and can result in a confusing display
Radar shows random signals in centre
Sea clutter usually appears as confusing,
random signals around your boat. High
waves will produce the maximum amount
of sea clutter.
You can optimize your radar window to
reduce the effects of sea clutter.