Furuno FR-2105-B - Manual (Page 114)

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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 detune of the equipment. Care should be taken in operating the
radar in the detuned condition 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 gain setting for long range detection should
be used, i. e., with a light background noise speckle visible.
A/C SEA control
For optimum range SART detection, this control should be set to the minimum. Care should
be exercised as wanted targets 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 nautical miles from the furthest dot back towards own ship.
Some sets have automatic/manual anti-clutter sea control facilities in which case the operator
is advised to use manual control initially until the SART has been detected. The effect of the
auto sea control on the SART response can then be compared with manual control.
A/C RAIN control
This should be used normally (i.e. 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
is advised to use manual control initially until the SART has been detected. The effect of the
auto sea control on the SART response can then be compared with manual control.
This information is excerpted from IMO SN/Circ 197 OPERATION OF MARINE RADAR FOR SART
DETECTION.
3.4 RACON (Radar beacon)
A RACON is a radar beacon which emits radar receivable
signals in the radar frequency spectrum (X or S band). There are
several signal formats; in general, the Recon signal appears on
the radar screen as a rectangular echo originating at a point just
beyond the position of the radar beacon. It has a Morse coded
pattern. Note that the position on the radar display is not
accurate.