Radar

What sets radar apart from the rest of the navigation suite

Radar is an active sensor: it transmits its own pulses and measures the echo, so it works independently of satellite signals, AIS transponders on other vessels, or visibility, which is why it remains the primary anti-collision and landfall tool when everything else fails. The main design choice within radar itself is frequency band. X-band (around 9 GHz) gives a shorter wavelength and finer resolution, so it is the standard choice for target discrimination and close-range collision avoidance. S-band (around 3 GHz) has a longer wavelength that penetrates rain and sea clutter far better, at the cost of coarser resolution, which is why SOLAS ships over a certain size are required to carry both: X-band for detail, S-band for reliable detection in heavy weather. A single-band fit is a real operational limitation, not just a cost saving, because neither band alone covers both jobs well.

Main components

Transceiver / scanner unit

Combines the transmitter, receiver and rotating antenna in one mast-mounted unit on modern solid-state sets, replacing the older separate magnetron transmitter and antenna arrangement found on legacy pulse radars.

Antenna

A rotating slotted waveguide array; longer antennas give finer bearing resolution, which is why larger vessels fit longer scanners than small craft.

Display and processor

Processes the returned echoes into the plan position indicator picture, runs target tracking (ARPA), and on integrated bridge systems overlays the radar picture onto ECDIS chart data.

Transmitter technology

Magnetron sets generate high-power short pulses and are simple and robust but wear out, since the magnetron itself is a consumable; solid-state pulse-compression sets use lower peak power over a longer, coded pulse, giving comparable range performance with no magnetron replacement and generally better short-range clutter performance.

Selection and sizing

• Vessel size and SOLAS category - determines whether one or two radars are required, and whether S-band is mandatory alongside X-band.
• Antenna length - longer antenna improves bearing discrimination between close targets, relevant in traffic-dense or coastal navigation.
• Transmitter technology - magnetron versus solid-state trades upfront simplicity against long-term maintenance cost and clutter performance.
• Integration - whether the radar needs to feed a full integrated bridge/ECDIS overlay or stand alone.

Regulations and class

SOLAS Chapter V sets the carriage requirements: cargo ships of 3,000 gross tonnage and upwards and passenger ships must carry two radar systems capable of operating independently, one of which must be a 9 GHz (X-band) set, arranged so that failure of one does not disable the other. Radar equipment must meet IMO performance standards and carry type approval referencing the relevant IEC test standard. Class and flag state surveys check the radar is operational, correctly interfaced to gyro/heading and speed inputs, and that the required second unit is genuinely independent, not sharing a single point of failure with the first.

Typical faults

• Magnetron degradation - a slow drop in transmitted power reduces detection range long before the set fails outright, often unnoticed until a comparison with the second radar reveals it.
• Antenna motor or bearing wear - irregular rotation speed distorts the picture and can eventually stop the scanner entirely.
• Waveguide or antenna joint corrosion - moisture ingress attenuates the signal, showing up as reduced range performance that is easy to mistake for a transmitter fault.
• Heading/speed input failure - a lost gyro or log feed degrades ARPA target tracking accuracy even though the radar picture itself looks normal.

What to look for in a supplier

• Type approval certificate confirming compliance with current IMO radar performance standards for the vessel's SOLAS category.
• Confirmed independence of the two required radar installations, down to separate power supplies where required.
• Spares and service support for the transmitter technology fitted, particularly magnetron replacement lead time if that technology is retained.

Compare both radars against each other regularly, not just against the chart - a slowly failing magnetron loses range gradually, and the difference only becomes obvious when the second, healthy set is checked side by side.