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Equipment Tests > Satellite Phones
Satellite Phones
Issue: March 2009
Words and photos by Robert Pepper
Off-road touring has an element of risk, so you use quality gear, acquire skills and plan. But sometimes that's just not enough, and problems crop up that you just can't handle.
In those cases talking to an expert or the authorities may be just what's needed. You might have a life-threatening injury on your hands, a dead vehicle that you are unable to fix, or be cornered by impassable roads with supplies running out. But for others communication is more mundane; many people conduct business remotely, and being contactable can mean the difference between a holiday going ahead or not. Or perhaps you're waiting on really important news but don't want to delay a trip.
So there's definitely a case for remote-area communications, and one of the most common solutions is a satellite phone, or satphone. Yes, there's other options, but portability and ease of use are satphone advantages.
So what is a satphone? Everyone knows what a conventional mobile is, one that works on the GSM network, but perhaps not how it works. The GSM network is a series of radio base stations all over the country, with a typical range of around 30km. Your mobile is a radio transmitter/receiver, and has sufficient power to transmit your call to the nearest base station, and from there it hooks in to the national telephone network and thus the world. The limitation is that you need to be close to a base station, which is obviously no good for outback travel, and the signal doesn't pass through or over hills, in part because it is broadcast from terrestrial stations.
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Satphones operate much the same way, but their basestations are satellites. Some, the like Thuraya system, have satellites in geostationary orbit (not moving relative to the planet), around 36,000km above the earth. These systems can cover the globe with just three or four satellites, but if one fails there is a coverage problem. The alternative is systems a low-earth orbit (LEO) system, as used by GlobalStar and Iridium. Iridium has 66 satellites at 780km above the earth, and GlobalStar 44 at around 1500km. These satellites circle the earth approximately once every 100 minutes, travelling in various directions. While the satellites can see a large part of the earth, not all satphones systems have truly worldwide coverage. In addition, satphone companies may be banned from offering service in countries such as Afghanistan, Iran, Iraq or Libya.
What the satellites do with a call signal when they receive it depends on the system. In the case of GlobalStar and Thuraya the satellite beams it directly back down to a base station on earth ("bent pipe"), so the satellite must be able to 'see' both the user and the base station. Iridium has a network of satellites and any one of them can pick up a call. If that satellite can't see a base station it passes the call to other satellites that can. From the base station the call is routed through the normal telephone networks.
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Words and photos by Robert Pepper
Off-road touring has an element of risk, so you use quality gear, acquire skills and plan. But sometimes that's just not enough, and problems crop up that you just can't handle.
In those cases talking to an expert or the authorities may be just what's needed. You might have a life-threatening injury on your hands, a dead vehicle that you are unable to fix, or be cornered by impassable roads with supplies running out. But for others communication is more mundane; many people conduct business remotely, and being contactable can mean the difference between a holiday going ahead or not. Or perhaps you're waiting on really important news but don't want to delay a trip.
So there's definitely a case for remote-area communications, and one of the most common solutions is a satellite phone, or satphone. Yes, there's other options, but portability and ease of use are satphone advantages.
So what is a satphone? Everyone knows what a conventional mobile is, one that works on the GSM network, but perhaps not how it works. The GSM network is a series of radio base stations all over the country, with a typical range of around 30km. Your mobile is a radio transmitter/receiver, and has sufficient power to transmit your call to the nearest base station, and from there it hooks in to the national telephone network and thus the world. The limitation is that you need to be close to a base station, which is obviously no good for outback travel, and the signal doesn't pass through or over hills, in part because it is broadcast from terrestrial stations.
read on below advertisement
Satphones operate much the same way, but their basestations are satellites. Some, the like Thuraya system, have satellites in geostationary orbit (not moving relative to the planet), around 36,000km above the earth. These systems can cover the globe with just three or four satellites, but if one fails there is a coverage problem. The alternative is systems a low-earth orbit (LEO) system, as used by GlobalStar and Iridium. Iridium has 66 satellites at 780km above the earth, and GlobalStar 44 at around 1500km. These satellites circle the earth approximately once every 100 minutes, travelling in various directions. While the satellites can see a large part of the earth, not all satphones systems have truly worldwide coverage. In addition, satphone companies may be banned from offering service in countries such as Afghanistan, Iran, Iraq or Libya.
What the satellites do with a call signal when they receive it depends on the system. In the case of GlobalStar and Thuraya the satellite beams it directly back down to a base station on earth ("bent pipe"), so the satellite must be able to 'see' both the user and the base station. Iridium has a network of satellites and any one of them can pick up a call. If that satellite can't see a base station it passes the call to other satellites that can. From the base station the call is routed through the normal telephone networks.
next page »
