General Remarks On Receiving Sart - Furuno MODEL 1622 Operator's Manual

Radar bandwidth
This is normally matched to the radar
pulselength and is usually switched with the
range scale and the associated pulselength.
Narrow bandwidths of 3-5 MHz are used with
long pulses on long range and wide bandwidths
of 10-25 MHz with short pulses on short ranges.
Any radar bandwidth of less than 5 MHz will
attenuate the SART signal slightly, so it is
preferable to use a medium bandwidth to ensure
optimum detection of the SART.
Radar side lobes
As the SART is approached, sidelobes from the
radar antenna may show the SART responses
as a series of arcs or concentric rings. These
can be removed by the use of the anti-clutter
sea control although it may be operationally
useful to observe the sidelobes as they may be
easier to detect in clutter conditions and also
they will confirm that the SART is near to the
ship.
Gain
For maximum range SART detection the normal
gain setting for long range detection should be
used, that is, with background noise speckle
visible.
STC control
For optimum range SART detection, this control
should be set to the minimum. Care should be
exercised as wanted target in sea clutter may be
obscured. Note also that in clutter conditions the
first few dots of the SART response may not be
detectable, irrespective of the setting of the
anti-clutter sea control. In this case, the position
of the SART may be estimated by measuring
9.5 nm miles from the furthest dot back towards
own ship.
Some sets have automatic/manual anti-clutter
sea control facilities in which case the operator
should switch to manual.
18
FTC control
This should be used normally (to break up areas
of rain) when trying to detect a SART response
which, being a series of dots, is not affected by
the action of the anti-clutter rain circuitry. Note
that Racon responses, which are often in the
form of a long flash, will be affected by the use
of this control.
Some sets have automatic/manual anti-clutter
rain control facilities in which case the operator
should switch to manual.
When the range to the SART is reduced to
about 1 nm, the radar display may show also the
12 responses generated during the fast sweeps.
These additional dot responses, which also are
equally spaced by 0.64 nm, will be interspersed
with the original line of 12 dots. They will appear
slightly weaker and smaller than the original
dots.
General procedure for detecting
SART response
1. Use the range scale of 6 or 12 nm as the
spacing between the SART responses is
about 0.6 nm (1125 m) to distinguish the
SART.
2. Turn off the automatic clutter suppression.
3. Turn off the Interference Rejector.

General remarks on receiving SART

SART range errors
When responses from only the 12 low frequency
sweeps are visible (when the SART is at a
range greater than about 1 nm), the position at
which the first dot is displayed may be as much
as 0.64 nm beyond the true position of the
SART. When the range closes so that the fast
sweep responses are seen also, the first of
these will be no more than 150 meters beyond
the true position.
Radar bandwidth
This is normally matched to the radar
pulselength and is usually switched with the
range scale and the associated pulselength.
Narrow bandwidths of 3-5 MHz are used with
long pulses on long range and wide bandwidths
of 10-25 MHz with short pulses on short ranges.