Radar Systems

Operating principle and bands

The radar transmits pulses from a rotating antenna and times the echoes. X-band works around 9.4 GHz and gives finer resolution of small targets. S-band works around 3 GHz and loses less signal in rain and sea clutter. A magnetron transceiver sends short, high-power pulses and needs a few minutes of warm-up. A solid-state transceiver sends longer, low-power pulses, recovers range resolution with pulse compression, and often adds Doppler processing to pick out moving targets.

Automatic target tracking, AIS target display and chart overlays all sit in the processor. On a drilling unit the radar also supports the unit's collision risk management, flagging vessels on a closing course toward the safety zone.

Key specifications

Down-mast transceivers sit in a dry room, which makes service easier, but they need a long waveguide on X-band, and waveguide is a common source of loss and water ingress.

Standards and what a used radar must meet

IMO resolution MSC.192(79) is the performance standard for radars installed on or after 1 July 2008. IEC 62388 is its test standard. It sets the radar category by ship size, with CAT 1 for the largest ships, and each category has minimum display and tracking performance. Display presentation follows IEC 62288 and environmental tests follow IEC 60945. A used radar installed as a replacement on a SOLAS ship must meet the standard in force at installation, so a pre-2008 radar approved to the older standard is a spare for an identical system, not a new installation.

Failure modes and inspection

• The magnetron loses output with transmit hours. Read the hours from the service menu and the date of the last change.
• Modulator boards and high-voltage supplies fail on magnetron sets.
• Antenna drive motors, gearboxes and rotary joints wear, and seawater gets past worn seals.
• Waveguide flanges corrode and trap water.
• Solid-state transceivers have no magnetron, but board-level spares disappear once the OEM drops the model.

A survey checks the performance monitor reading, magnetron current, tuning, heading line alignment against a visual bearing, and the bearing and range accuracy against known targets. Run the antenna under power and listen to the gearbox. Open the antenna housing and check for salt and moisture.

Documentation

• Type-approval certificate naming the model and software.
• Installation report with antenna height, heading line alignment and blind sector diagram.
• Magnetron replacement log or transmit hours.
• Last annual service report from an OEM-authorised agent.
• Software licence and configuration backup.

Integration with your unit

The radar needs stabilised heading from a gyrocompass or transmitting heading device at the rate IEC 62388 asks for, position from GNSS, and speed through the water from the speed log for collision-avoidance tracking. It sends tracked targets to ECDIS and alerts to the bridge alert system. Antennas, transceivers and processors usually work only within one OEM product line and generation. An interswitch unit that lets two displays share two transceivers must also come from the same family.

Refurbishment, used or surplus

OEM workshops exchange transceivers, replace magnetrons and overhaul antenna gearboxes. A used transceiver or antenna of the model already installed is a sound spare. When the processor or display is out of support, a complete unused surplus or new system costs less over its life than chasing parts. Older magnetron sets remain serviceable where the magnetron is still made.

Related equipment

Radars take heading from gyrocompasses and position from GNSS receivers. Naventr can get the magnetron hours and installation report from the Seller before you make an offer.