MARINE RADAR TYPES
X Band or 3 cm radar
Radar wavelengths are expressed in centimetres, the commonest commercial marine radar being 3 cm (actually 3.1 to 3.2 cm). This corresponds to a frequency of 9300 to 9500 megahertz (millions of cycles per second) and is called X-band radar.
A 3 cm radar requires a smaller scanner to achieve the desired beamwidth and definition as compared with a 10 cm radar. X-band radars are particularly suited to coastal navigation and pilotage due to their high picture definition and quality. On the negative side a 3 cm radar produces more side lobes than a 10 cm radar and the radio waves are not as refracted to the same extent. Therefore they will not achieve the same range as a 10 cm radar.
S Band or 10 cm radar
Another common marine radar wavelength is 10 cm (actually 9.2 to 10 cm) with a frequency of 3000 to 3246 megahertz. This is known as S-band radar. A 10 cm radar will require a scanner up to 5 metres long to focus the beam. However, once produced the beam will produce fewer side lobes and travel further along the surface, resulting in a greater maximum range. Another advantage of S-band radars because of their longer pulse length and greater power is that they will be less affected by attenuation than X-band radars.
