|Of Seas and Satellites|
2: Satellite Communication continued
By Tim Clark — March 2001
Of Inmarsat's several services, its Mini-M is best suited for pleasureboats. It is versatile and relatively inexpensive and can be accessed with equipment that won't overload your boat. Most satellite terminals--that is, phones--on the market are designed to operate with a specific network. Phones engineered for Inmarsat Mini-M include KVH's Tracphone 25, Nera's Worldphone Marine, and Thrane & Thrane's TT-3064A Capsat Maritime Telephone. All three phones, which are priced in the neighborhood of $6,000, are compact--about the size of a laptop--and their exterior antennas are also small: KVH's is just 10 inches in diameter and weighs 11 pounds, Nera's is 103/4 inches and also 11 pounds, and Thrane & Thrane's is a mere 81/4 inches and just under five pounds. Before Mini-M, satellite-tracking antennas for Inmarsat had to be much larger, so mounting them on smaller boats was problematic.
Telephoning with these terminals is as simple as making an international call: You start with the country code, then enter the area code, then the number. The four ocean regions covered by Inmarsat's satellites have number codes like those of individual countries, so calling your boat in the Indian Ocean from the United States is just like calling France or Fiji. Per-minute costs vary depending on what subscription plan you use. On average, a one-minute call from your boat to a fixed phone on land or vice versa runs about $2.25. Calling from one satphone to another can be nearly twice as expensive.
In light of such charges, it's easy to see the importance of Mini-M's fax and e-mail capabilities. All three phones mentioned above can be connected to a conventional fax machine, PC, or laptop. For e-mail, plugging a PC into the Mini-M system is just like connecting to a modem at home. You can even use the same dial-up-networking software and your accustomed Internet service provider. However, because the rate of data transfer is so slow--just 2.4 kb per second as opposed to the 56 kb per second standard on most modems these days--you'll want to take steps to minimize your time online. Obviously, you should compose your messages offline. Word processor files sent as attachments are relatively bulky (and therefore take longer to transmit), so it's better simply to cut and paste text onto your e-mail program. Graphs, charts, and other graphics in spreadsheet applications also take up a lot of kilobytes, so consider sending only raw data. If you must mail attachments, send them as compressed files using a program such as WinZip or Pkzip, which can reduce the size of text files by 50 percent.
It's also important that transmissions of incoming data be cost-effective. Toronto-based Stratos, one of many telecom companies marketing service plans in partnership with satellite networks, offers an Internet service designed specifically for mobile satellite users that provides built-in data compression to reduce transmissions by as much as 60 percent. Another feature lets you view only e-mail header information so that you can choose which messages to download in full.
This article originally appeared in the January 2003 issue of Power & Motoryacht magazine.