User's Manual

Operation of marine radar for SART detection

Radar Range Scale

When looking for a SART it is preferable to use a range scale between 6 and 12

nautical miles. This is because the spacing between the SART responses is about

0.6 nautical miles (1125 metres) and it is necessary to see a number of responses

to distinguish the SART from other responses.

SART Range Errors

There are inherent delays in the SART responses; the SART has a trigger delay

and may also have to sweep through the whole radar band before reaching the

frequency of the search radar. At medium ranges of about 6 nautical miles the

range delay may be between about 150 metres and 0.6 nautical miles beyond the

SART position. As the SART is approached the radar delay of the first dot should

be no more than 150 metres beyond the SART position.

Radar Bandwidth

This is normally matched to the radar pulse length and is usually switched with the

range scale and the associated pulse length. Narrow bandwidths of 3.5MHz are

used with long pulses on long range and wide bandwidths of 10-25MHz with short

pulses on short ranges. Any radar bandwidth of less than 5MHz will attenuate the

SART signal slightly so it is preferable to use a medium bandwidth to ensure

optimum detection of the SART. The Radar operating manual should be consulted

about the particular radar parameters and bandwidth selection.

Radar Side Lobes

As the SART is approached side lobes from the 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 side lobes as these will confirm that the SART is near to the ship.

Detuning the Radar

To increase the visibility of the SART in clutter conditions the radar may be detuned

to reduce the clutter without reducing the SART response. Radar with automatic

frequency control may not permit manual detuning of the equipment. Care should

be taken in operating the radar detuned, as other wanted navigational and anti-

collision information may be removed. The tuning should be returned to normal

operation as soon as possible.

Gain

For maximum range SART detection the normal maximum gain should be used.