Satellite Communications

With the ability to make and receive telephone calls, send and receive emails and even have internet access from almost anywhere on the planet, satellite communications is now a well established means of communications on most ocean going yachts. Data rates are relatively slow compared to mobile 4G/5G and fixed line internet connections, but even so having the ability to receive vital weather information and communicate back to shore, most yachtsmen are choosing to go with some sort of satellite communications to meet their every day communication needs.

Satellite communications should not be considered as a direct replacement for terrestrial MF/HF SSB communications. Communications with yachts, ships and coastguard are free via terrestrial MF/HF SSB radio, compared with satellite communications which you pay for the connection. Therefore both satellite and terrestrial MF/HF SSB communications should be considered to be complementary to each.

Satellite communications can provide telephone one-to-one communication and internet. Services like the Iridium PTT (press-to-talk) give the capability of providing one-to-many communications via what is call talk-groups. When one station transmits all other users within the talk-group can hear the announcement. The equipment is easy to use, just like using a handheld VHF radio and the cost of the equipment is relatively low compared to a terrestrial MF/HF SSB installation but Iridium PTT does incur monthly running charges.

The Icom SAT-100 is an approved Iridium PTT portable devices which can be used by anyone on land or at sea.

Organizers with large fleet of yachts are now considering using Iridium PTT over terrestrial MF/HF SSB, as Iridium PTT provides reliable one-to-many communications at reasonable cost and does not require any qualification or technical ability in the operation of the equipment.

Satellite facts

Life times - Satellites have a limited life time of less than 20 years, dependent on fuel and orbit.

Satellites burn fuel to keep in the correct orbit. Low orbiting satellites are being pulled back toward the earth by gravity and hence have a short life time. Higher orbiting geostationary satellites last about 20 years before running out of fuel and drift out into space.

Number of calls - The satellite is basically a telephone exchange, it can only handle a limited number of calls.

Low orbiting satellites handle less calls per satellite, but there are more satellites. Higher orbiting satellites can see more of the earth's surface and hence designed to handle a high number of calls, between 5000 to 25000 calls per satellite with fewer satellites.

Coverage - Depends on technology deployed.

Bent pipe technology is the most common due to low cost and small size. This is when all calls are passed to a ground station for processing. On low orbiting satellites, if the satellite cannot see a ground station then it cannot connect calls.

Interlink satellite technology uses larger and more expensive satellites. This is when satellites can transfer calls between themselves without going via a ground station.

Mobility - If the satellite is not in direct view the expected poor service with slow or even dropped calls. Therefore the satellite antennas board the yacht needs to be above deck with a 360 degree view of the sky with no obstructions to receive and make calls.

The low transmit power from your satellite phone needs to travel a long way. Low orbiting satellites are in the region of 500 miles above your head and move quickly across the sky. Geostationary satellites are some 22000 miles above the equator and you need a clear path between you and the satellite for your signal to reach it.

Reliability - In the main good, but like any other mobile phone technology do expect to lose/drop calls.

Systems cost - It is very expensive to put satellites up there and maintain them.

Satellites are designed to be reliable, you cannot send someone up there to fix them when they go wrong. Launch costs are high and each payload carries between 3 to 10 communication size satellites.

Satellite phones do suffer from a lot longer time delays compared to the terrestrial mobile phone.

Mobile satellite providers

Iridium - Offers global coverage and provides reliable phone and data connections with data speeds range from 2.4 kbps to over 1 mbps.

Iridium GO! Marine - Provides a WiFi to satellite hotspot at relatively low running costs.

Iridium Certus - Advanced multi-service platform offering high speed (>1mps) data throughput,

Inmarsat - A service targeted towards the marine users offering good ocean region coverage and with telephone and data with fast broadband internet access.

Fleet broadband with antenna from 33 to 80 cms and broadband speeds from 150 kbps to 500 kbps. The bigger antenna is used for faster data.

Global Xpress operates on a frequency range of 30 GHz and delivers data at rates of up to 50 Mbit/s via a 60cm or one metre dish.

Globalstar - Anything but global! Poor global ocean region coverage, phone and data service.

Thuraya - European, Middle East and Far East coverage, emails and data services for instant satellite access to the Internet.

There are a number of new satellite services being developed which will provide fast internet access, these include Starlink and OneWeb. Whether these satellite systems will be suitable for small boat marine communications is yet to be seen.

Satellite phone call charges

Telephone call costs range from $0.30 to $2.00 per minute and even more on some systems.
Beware of call costs to your satellite phone from shore, it is usually cheaper to make the call than to receive a call!

Data charges are very expensive. Inmarsat FleetBroadband charge around $12 per Mbit or $12000 per Gbit, which is about 1000 times more than over a 3G/4G mobile phone!
Also inter satellite calls between different satellite networks are expensive.

Airtime charges (running costs) are expensive. Therefore to keep cost down it is worth considering using an email compression service such as SailMail.

Satellite Data via satellite phone systems. For speech, a narrow bandwidth of only 2400 Hz is required. Some early satellite phone systems (Iridium and Globalstar) were only designed to handle voice communications which uses a very narrow bandwidth.

The narrow band restricts the amount of data which can be sent, data rates range from 2.4 k bits to 9.6 k bits per second depending on the service provider.

For the average cruising yacht, one of the most cost effective satellite solution is the Iridium GO! Marine, which provides a WiFi to satellite hotspot. You can have 5 devices (PC computer, tables, mobile phones) connected via WiFi to the hotspot, these devices can then have access to the satellite. There are some limitations, only one device can use the satellite link at a time and you can only use approved applications.

One of the approved applications for the Iridium GO! is SailMail’s Airmail3 software package, which gives the ability to send and receive email, request weather charts and GRIB files and send position reports.