2. RADAR OBSERVATION
2-7
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 scales and wide bandwidths of 10-25 MHz with short
pulses on short ranges.
A 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 can 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 can be operationally useful to observe the
side lobes as they may be easier to detect in clutter conditions and also they will con-
firm that the SART is near to own ship.
Note: SART information excerpted from IMO SN/Circ 197 OPERATION OF MARINE
RADAR FOR SART DETECTION.
2.4 RACON
A RACON is a radar beacon that emits radar receivable signals in the radar frequency
spectrum (X- or S-band). There are several signal formats; in general, the RACON sig-
nal appears on the radar screen as a rectangular echo originating at a point just be-
yond the position of the radar beacon. It has a Morse coded pattern. Note that the
position on the radar display is not accurate.
2.5 Radar Target Enhancer (RTE)
An RTE is a radar transponder mounted on navigation buoys and masts of small crafts
to significantly improve their detection by radar. Unlike a SART or RACON, which are
passive, the RTE receives a radar signal, amplifies it and re-transmits it, with the in-
tention of making the target's signal look larger on a radar display. The RTE is avail-
able in X-band and S-band types.
Echo description
RACON signalRACON signal
RACON stationRACON station
Echoes on the radar screen
Your ship positionYour ship position
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