Signals around the world

One of prime needs for any voyager is the ability to communicate. In the days of Joshua Slocum there was little other than signal flags and speaking trumpets. The modern voyager, however, can send his or her signals around the world. There is a wide array of communications choices. VHF DSC

VHF digital selective calling (DSC) is a technique for automating the calling and channel-selection process. This method eliminates calling and channel-selection chatter, improves Mayday signaling when the radio is interfaced to a GPS receiver, and generally makes a VHF radio easier to use.

Adoption of DSC technology has been a classic chicken-and-egg situation. Mariners haven’t bought DSC radios because only a few models were available, and manufacturers haven’t produced these units due to a lack of consumer demand. Even the Coast Guard has been slow in installing this radio technology in its communications stations.

However, since many commercial vessels are required to have DSC capability under the Global Maritime Distress and Safety Signaling (GMDSS) rules, sales have picked up in the face of international deadlines for compliance (the U.S. deadline was late January). For example, SEA Inc., a manufacturer of HF and VHF radios, recently reported that its VHF DSC radio, the SEA 7157, is selling briskly to commercial users.

One development that could spur VHF DSC sales is the inauguration of a nationwide VHF DSC telephone interconnect system by Maritel of Gulfport, Miss. In the past few years Maritel has bought up independent VHF marine operator stations and integrated them into a national network. Now Maritel is building a VHF DSC-based system that will reportedly allow mariners to make automated phone calls without the need for a human operator, plus send faxes and e-mail at 9,600 bps. This system will use 250 towers on the U.S. East, Gulf, and West coasts that are due for construction this year. The system is scheduled for completion in 2000.Marine HF SSB/ham SSB

The big news in marine HF SSB for voice communications has to be the closing of ATandT’s three high-seas radiotelephone stations: WOO in New Jersey, WOM in Miami, and KMI in California. For decades, these stations have connected mariners with the land-based telephone network. According to ATandT, this service is not profitable, and the company pulled the plug at the end of February. ATandT sent a letter to its high-seas radio customers and urged them to sign up with ATandT’s mini-M satellite communication service.

The closure of WOO, WOM, and KMI leaves the non-ATandT-owned station WLO in Mobile, Ala. (, as the sole supplier of ship-to-shore HF SSB radiotelephone service in the U.S. According to spokesman Curt Fauver, WLO is eager to welcome HF radiotelephone users. “I’ve received many, many calls since the announcement,” said Fauver. “It’s been quite hectic around here.” WLO can operate 25 to 30 transmitters at a time, so it shouldn’t be overloaded by any extra traffic it receives from former ATandT users.

While the availability of voice HF SSB has decreased, digital HF is has seen continued development. Sending text messages (as opposed to voice) via HF has been around for a long time. Simplex telex over radio (SITOR) is a text-based message technique that has been used for decades and is still in use today. The change in text messaging has been the use of digital signal processing. Audio signals are converted into digital form and then quick-marched through a variety of digital filtering techniques to extract the usable signal from the noise. This has produced digitally enhanced HF messaging formats like Clover, Pactor I and Pactor II. These techniques allow text messages (e-mail) to be sent and received even at low signal to noise ratios.

There are three companies offering HF e-mail services: PinOak Digital, Globe Wireless, and WLO’s ShipEmail. Each of these systems will allow you to send and receive Internet e-mail.

PinOak ( was recently awarded the call sign WPC by the FCC, signifying PinOak’s common carrier status. PinOak also added the capability for its users to receive gridded binary (GRIB) files of 16-color weather data. These GRIB files can be used with route-planning software while offshore. These files can be downloaded for $2 to $3 each. PinOak now reportedly offers the capability to send and receive messages in real time (like Internet relay chat)a useful capability for medical emergencies, for example.

Globe Wireless (, which uses both SITOR and Clover modulation techniques, has expanded its worldwide network to 15 stations, including a new station in South Korea. Recently, Globe Wireless has concentrated on selling its services to the commercial market. However, the company will still service recreational customers.

There is another option called SailMail for marine SSB users who would like to send e-mail messages. SailMail ( is a non-profit association that operates a private coast station, call sign WRD719, from Palo Alto, Calif. By becoming a member of the association, for a fee of $200, you can send and receive e-mail messages from the station, which operates via SITOR and Pactor II using a free software package called AirMail. The SailMail station operates on six HF frequencies and reportedly can handle connections at a range of 7,000 miles form Palo Alto. You don’t need to be a ham to use this service, only a member of the SailMail Association.

In ham radio developments, the requirements for getting a ham license are reportedly going to be reduced. One of the advantages of having a ham license is the capability to send text and e-mail messages using up to 60 ham mailbox (MBO) stations worldwide (see story on ham-based email in this issue). These stations will send and receive e-mail messages from and to the Internet and between boats. Other than the cost of a radio and modem (also called a terminal node controller or TNC) these services are free. Satellite communications

The satellite communications option for those voyagers who want the small on-board user equipment, worldwide coverage, and automatic distress signaling is the text-based Inmarsat C system. Recently, Inmarsat announced that 10,000 Inmarsat C units have been commissioned.

Inmarsat C sends text messages, data files, and e-mail to the Internet, but it does not carry voice, so you can’t make a phone call using Inmarsat C. However, its satellite system is reliable, and you can send and receive messages without having to worry about the vagaries of HF radio, like determining the best frequency and dealing with atmospheric noise.

One of the biggest advantages of Inmarsat C is its ability to send a distress message at the touch of a button. A GPS unit can be plugged into an Inmarsat C transceiver, or you can purchase a Inmarsat C unit that has a built-in GPS receiver (these units use combined antennas that can receive both signals). With this positioning input, pressing the distress key will send a message that will be directed to the nearest Rescue Control Center (RCC). The staffers at the RCC will know both your identity and your position.

You can set up an account with a variety of Inmarsat service providers, such as Comsat from the U.S., British Telecom from the U.K., Station 12 from the Netherlands, etc. It can pay to shop around to get the best deal. How do you know where to shop? The easiest way to get a good deal is to enlist the help of an independent satcom dealer who will know how to get you the best price on equipment and service.

Another text-based approach is the Orbcomm system. This satcom system uses a constellation of 28 low-Earth-orbit satellites for sending short text messages (text messages are limited to 2,000 characters, or about 300 words). Users can employ the combined Orbcomm transceiver and built in GPS, made by Magellan and called the GSC 100, either as a handheld unit on deck or mounted down below at the nav station and using a remote antenna. Like Inmarsat C, Orbcomm is a worldwide system, and the built-in GPS receiver allows you to position-stamp your messages.

If you must have voice communications, Inmarsat also offers another system called Mini-M (this is the sequel to Inmarsat’s M system, which was designed for small commercial vessels and large yachts.) The Mini-M antennas are small enough to put on a 30-foot yacht and will give users voice satcom capability for large areas of the globe. Unlike Inmarsat C, however, Mini-M is not worldwide. It uses a series of spot beams to provide coverage for those areas with the most customers. The Southern Ocean and other areas are not included in the coverage scheme. Mini-M also doesn’t have the easy distress features included in Inmarsat C. The best thing about Mini-M is that you can make a standard phone call to any land-based phone anywhere within the coverage area.

In an effort to include the best of both of these systems, the Danish equipment manufacturer Thrane and Thrane is now offering a satcom unit called the TT3000CM that combines Mini-M and Inmarsat C.

Yet another satellite system for voice communications is the SkyCell system, providing regional coverage for North America. SkyCell, formerly known as AMSC, uses a geostationary satellite with spot beams that provide service to coastal areas of the U.S. and Canada out to roughly 200 miles. There are also spot beams that cover Central America, the Caribbean, and Hawaii.

The equipment for the SkyCell service is made by Westinghouse. The phone unit is similar to a Mini-M setup, with the antenna being a bit smaller. SkyCell does offer you the advantage of lower-cost phone calls, but it is a regional systemyou can’t use it worldwide. For those voyagers who plan to spend most of their time relatively close to the U.S. coast, SkyCell could be a good choice for satellite voice communications. The much-heralded Iridium satcom system (see accompanying story) is now operational. Iridium, whose major partner is Motorola, has launched a constellation of 66 low-Earth-orbit satellites. Since these satellites are a mere 400 miles or so above the Earth, rather than in the 23,000-mile-high orbits required for geostationary satellites, it’s possible for Iridium users to make calls with phones that are only a little larger than the average cell phone. Talking on an Iridium phone while in mid-ocean may be convenient, but it’s also expensive. For most voyagers the cost of Iridium will probably outweigh the ease of making phone calls worldwide. In addition to being the last year of the old millennium (remember, there was no year 0, so the millennium doesn’t turn until 2001) the year 2000 should see the introduction of two new satellite communications systems: ICO, which will use 10 medium-Earth-orbit (10,000 miles high) satellites, and Globalstar, a 48-satellite low-Earth-orbit (900 miles high) system. Both of these systems will be similar to Iridium: users will use handheld phones anywhere worldwide.

The result of all this change is more communications choices for ocean voyagersand more choices are to come as new systems come on line in the next five years.

By Ocean Navigator