VSAT installation on a vessel is two jobs joined by one cable run. Above deck sits a stabilised antenna in a radome, below decks a modem, router and rack. Alongside, with two technicians, a marine VSAT installation takes four to six working days once the survey is out of the way.
The order of work is survey, approvals, foundation, cabling, antenna fit, commissioning, operator line up, integration and handover. Everything after the survey inherits it, because antenna position fixes blockage for the ship's life.
The two halves of a VSAT installation on a vessel
The above decks half is the stabilised antenna, its pedestal and the radome, usually on the monkey island or a mast platform. Below decks sit the antenna control unit, modem, router, a UPS and the patch into the ship network. On a typical merchant ship that means one 60 cm to 1.0 m Ku band terminal, often with a flat panel LEO terminal beside it feeding the same rack. Offshore units run 1.5 m reflectors, sometimes two so one always sees past the mast.
The survey decides the outcome
Once the stool is welded and the cable glanded through four decks, nobody is moving it. A VSAT site survey exists to produce one drawing. Stand at the proposed position, at radome centre height. Then record with compass and inclinometer the elevation of every obstruction through 360 degrees in 10 degree steps, taking in masts and funnel, crane booms stowed and working, davits, whips and the radar platform. Plotted round the compass rose, that becomes the antenna blockage map. Overlay the elevations the trading pattern needs. A ship in the Gulf works the geostationary arc at high elevation, commonly 40 to 60 degrees depending on satellite longitude, and tolerates a lot of structure. In the North Sea she may work at 20 degrees, where a boom topping out at 25 degrees on the wrong bearing drops the link on that heading. Check the beam maps for the regions in that pattern before the position is fixed.
What separation distances should you plan for?
- Radar comes first. Keep the radome out of the scanner plane, 15 degrees below it where structure allows, and 3 m clear of an X band array. A radome in a radar beam collects interference now and a damaged low noise block later.
- Allow around 3 m to another Ku or Ka terminal, more from an MF or HF whip.
- The control unit and modem carry a compass safe distance on the plate, commonly 1 m to 2 m.
- Keep clear of the funnel plume as well, since soot costs you signal and heat ages the radome.
- Radiation hazard. On axis power density in front of a 1 m Ku band antenna with a 25 W block up converter exceeds general public exposure limits well beyond arm's reach, and the near field alone extends several metres. Take the hazard distance from the manufacturer's manual, mark the zone on deck, and fit a transmit inhibit switch anyone going aloft can reach.
Foundations and platform stiffness
A stabilised antenna corrects roll, pitch and yaw. It cannot correct a platform that flexes at 10 or 15 Hz. Put a 1.5 m antenna on a slender mast platform and that resonance couples into the tracking loop. You get pointing error and packet loss at sea, where chasing it costs sea time. Stiffness matters as much as strength. Build the stool from plate and gusset it, then land it on a deck girder. Level it within 1 degree and punch mark the fore and aft line so the heading offset has a physical reference. Get the foundation drawing to class before anyone strikes an arc. Loads are higher and deck space tighter on offshore energy installations, where a purpose built pedestal is normal.
How do you plan the cable route and the loss budget?
Most systems carry receive, transmit, DC power and control on one coax pair at L band, roughly 950 to 2150 MHz, where coax is lossy. At 1.5 GHz, LMR400 or equivalent costs about 16 dB per 100 m and RG214 closer to 26 dB. Loss climbs roughly with the square root of frequency, so at the 2150 MHz top of the band those figures become nearer 19 dB and 31 dB. Thin RG223 belongs in jumpers. Work the cable loss budget as a sum of the run at the top of the band, half a decibel per connector, every feedthrough, and several decibels held in hand for ageing connectors and a wet radome. Most terminals tolerate 20 to 25 dB in total. But on a long run the DC drop feeding the antenna and its block up converter bites before the RF number does, which is why we move to a fibre kit past about 50 m.
Then the route. Run it in dedicated tray away from radar trunks and high current runs, bend radius at least ten times the cable diameter, a drip loop before every gland, approved glands at each penetration, and two metres of service loop left at the antenna.
Grounding, power and heat below decks
Bond the pedestal to the hull with a flat strap of 25 mm by 3 mm tinned copper, as short and straight as the structure allows. A long coiled round wire has too much inductance to bond at RF. It produces the intermittent lock instability that gets blamed on the satellite six months later. Below decks, take modem, control unit and router to a single earth point.
Feed the system from a dedicated breaker. Total draw is 500 W to 1.5 kW depending on antenna size and transmit power. The above decks unit takes most of it. The rack is roughly a fifth of that, so 100 to 300 W of heat into the space. Size the UPS for 30 minutes and put the switch and router on it as well as the modem. The failure mode is familiar. The modem rides through the blackout, the switch does not, and the bridge reports a total outage.
Rack the gear where there is air movement and access to the back, usually the radio room. Fit vents or a fan if the space is closed. Sealed into an unventilated locker on a ship trading the Red Sea in summer, a rack passes 50 C inside, where modems throttle and then fail early.
What class and flag approvals do you need?
Start this early, because none of it is difficult and all of it burns calendar time. VSAT sits alongside GMDSS and does not replace it, so the GMDSS installation stays untouched. Expect class approval for the foundation drawing where it welds to strength structure, hot work permits, approval for penetrations through fire and watertight boundaries, and a licence amendment for the ship station. Requirements and timescales vary by flag and class society, so confirm the current position with the flag administration and the class surveyor attending the vessel.
The install sequence stage by stage
This is the sequence our professional services team works to, and what finished looks like at each stage.
- Site survey. Done when you hold a signed report covering antenna position, blockage map, cable route and length, power source and earth point.
- Design and approvals. The foundation drawing is approved, permits are in hand, the licence application is lodged.
- Mobilisation. The terminal and its installation kit are on the quay, checked against the packing list, glands and all.
- Foundation. Signed off once the stool is welded or bolted, tested where class asks, levelled within 1 degree and marked for heading.
- Cable pull and termination. You are finished when continuity and insulation test clean, measured loss is on the schedule, and penetrations are restored.
- Antenna fit. Done when the radome is torqued to specification and the antenna drives through full travel without snagging its loom.
- Below decks fit and power up. The rack is secured, the UPS is load tested with everything connected, and the terminal passes self test.
- Pointing and acquisition. The terminal locks to the intended satellite at the receive level the operator predicts for that beam.
- Cross polarisation line up. Complete once the operator has signed off isolation and transmit levels and enabled the terminal.
- Network integration. Crew and business traffic separated, failover proven by pulling a cable, and the NOC able to reach the terminal remotely.
- Underway verification. Done when the link holds through a full swing of heading and the blockage arcs match the survey.
- Documentation and handover. Drawings, report and IP plan aboard and ashore, the crew trained, and spares stowed where the electrician can find them.
Commissioning, cross polarisation and the operator line up
With a gyro heading and a GPS fix at the control unit, the antenna will search and lock. Lock is the first step of maritime VSAT commissioning, with most of the work still ahead. Check receive level and Es/No or SNR against what the operator predicts for that beam. A terminal 2 dB low is a fault to find before anyone goes home. Then comes the cross polarisation line up call, an unmodulated carrier with skew adjusted until cross polar isolation nulls, usually better than 30 dB, then a modulated carrier so the operator can set your transmit power.
The classic failure is a bad heading offset. The antenna locks two degrees off the satellite you paid for, deck indications look healthy, and the first news is an interference report and an order to stop transmitting. Confirm the satellite identity first. Intellian marine antennas vary between models in how they take a heading feed, so work from the manual.
How does the terminal integrate with the ship network?
Keep crew and business traffic on separate VLANs, shaped so crew usage cannot starve the operational VPN and voice. Navigation and machinery systems stay off that network. Where a vessel carries more than one link, VSAT plus a LEO terminal plus 4G near shore, an SD WAN router handles policy and failover, turning a hybrid link into one managed service. A Peplink router sits in the same rack on most of the hybrid installs we fit.
Common installation mistakes and what they cost
| Mistake | Consequence |
|---|---|
| Antenna sited for welding access, before the blockage map existed | Link drops on certain headings for the life of the ship |
| Long coax run where a fibre kit belonged | Voltage at the antenna sags and the block up converter drops out under load |
| Bond made with a long round wire | Intermittent modem lock nobody can reproduce alongside |
| UPS on the modem, switch and router unprotected | Every blackout reads as a total outage on the bridge |
| Rack sealed into an unventilated locker | Thermal faults and early failure in warm trading areas |
| Heading offset entered without a measured reference | Wrong satellite, interference report, transmit disabled |
| Deck penetration not restored to class standard | A survey finding, and rework you pay for twice |
How long does it take, alongside or in drydock?
| Stage | Alongside, two technicians | Yard period or drydock |
|---|---|---|
| Survey, if not already done | 0.5 to 1 day | 0.5 to 1 day |
| Foundation fabrication and fitting | 1 to 2 days, subject to permits and cargo work | 1 to 1.5 days, staging already up |
| Cable pull and termination | 1 to 1.5 days | 1 to 1.5 days, panels open |
| Antenna and below decks fit | 1 day | 1 day |
| Commissioning and operator line up | 0.5 to 1 day | 0.5 day, only after undocking |
| Network integration and handover | 0.5 day | 0.5 day |
| Typical total, survey already done | 4 to 6 working days | 4 to 5 days across the period |
Where the survey happens on the same visit, add half a day to a day, so 4.5 to 7 alongside and 4.5 to 6 in the yard. Alongside looks slower on paper but often finishes sooner, because you commission the day the physical work ends. The real constraint is permits and port stay. A dock is easier physically, but you cannot point at a satellite through a dock hall roof, so the line up waits for undocking.
Documentation, handover and the support plan
The handover pack is drawings, the cable schedule with measured losses, the IP plan, licence copies and a commissioning report carrying receive level, cross polar isolation, transmit power and satellite. Then spend ninety minutes on the crew handover with the electrician and the officer who owns the system, covering what the lights mean and how to raise a ticket an engineer can act on straight away.
Leave a spares kit aboard, covering jumpers, connectors, glands and the tools to fit them, with a spare modem and block up converter on ships trading far from support ports. Agree the support arrangement, 24/7 NOC monitoring and remote support, and which ports can take an attending engineer.
Your next step
Send the general arrangement plan, the profile drawing, photographs of the monkey island and mast platform, and the trading pattern. Talk to our maritime engineering team and we will come back with a survey scope and a realistic window for the next port call or yard period.
