GNSS Antenna Placement on Vessels
Almost every system on a modern vessel depends on GNSS. Chartplotters, AIS, DSC radios, autopilots, VMS units and satcom terminals all need a reliable position. The antenna is small and easy to fit, so it often goes wherever there is space left on the rail. That is usually not the best place for it.
A clear view of the sky
GNSS antennas need an unobstructed view of the sky down to a low elevation angle. Masts, radar scanners, satcom domes and the wheelhouse itself all block satellites in some directions. Fewer visible satellites mean poorer accuracy and longer times to regain a fix after a dropout.
Keep clear of radar and satcom
- Radar: mount the GNSS antenna below the radar beam and away from the scanner. Radar pulses can overload the GNSS receiver.
- Satcom transmitters: L-band and VSAT terminals transmit close to GNSS frequencies. Keep a good distance and avoid placing the GNSS antenna in the satcom's beam.
- VHF and AIS antennas: keep at least a metre of separation where possible.
Avoid multipath
Signals reflected off superstructure, metal decks and the sea surface arrive at the antenna slightly later than the direct signal. This multipath degrades accuracy. Mounting the antenna on a short pole above nearby metalwork, rather than flat against a bulkhead, usually reduces the problem.
One antenna or several?
Larger vessels often run several GNSS receivers. Each can have its own antenna, or a splitter can feed several receivers from one high-quality antenna. A dedicated antenna for safety-critical systems such as AIS keeps them independent of other equipment. Combined units like the VHFGPS4, which pairs marine VHF and GNSS in one 1.1 m housing, save space on small craft.
Antennas in the Renair range
- UNISAT: universally mounted active GNSS antenna for navigation and tracking.
- SATFIX-1: compact active 5 V GNSS antenna.
- Browse the full GNSS antenna range.
Cabling and power
Active GNSS antennas take power over the coax, so check that splitters and surge arrestors pass DC. Keep cable runs within the antenna's gain budget, and seal every outdoor connector. Mount on stainless steel hardware such as the RAIL MOUNT LW 1"-14NF.
Frequently asked questions
How far should a GNSS antenna be from a radar?
Mount it below the radar beam and away from the scanner. Follow the radar and GNSS manufacturers' guidance on minimum distances.
Can several receivers share one GNSS antenna?
Yes, through a GNSS splitter. Check that the splitter passes DC to power the antenna and that the gain budget covers the splitter loss.
Why does my vessel lose GNSS position near the quay?
Buildings, cranes and the vessel's own structure can block satellites and cause multipath. A higher antenna position with a clearer sky view usually helps.
For the wider picture, read our GPS and GNSS antenna guide. For help specifying vessel antennas, contact sales@renair.co.uk.
Understanding the Innovative Technologies Behind Our Antenna Solutions
At Renair, we utilise cutting-edge technology to design antennas that excel in performance and reliability. Our manufacturing process incorporates rigorous testing to ensure each product meets the highest standards. This commitment to quality guarantees that our antennas provide seamless connectivity for a variety of applications.
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