Furuno GD-1700, Operator'S Manual

Page: 143 / 249

3. RADAR OPERATION
3-49
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 (if applicable).
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.
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 sidelobes
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 [A/C 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.