Almost a decade ago when I sailed across an open stretch of the Pacific I was introduced to an inexpensive radio connected to a laptop to send email. Although our boat was thousands of miles from land for days, we had some comfort knowing a brief email message could be sent to friends and family at very little cost.
The technology we used was based on Single Sideband (SSB). The reason email can travel so far on the radio we had on the boat is because of efficiency. The standard radio broadcast transmitter with 4-kW can put only half its power to signal (2-kW) and then it splits power again between two sidebands (1-kW).
A single sideband does not bother with use of the carrier and the other sideband so it can put all power into a single sideband (thus the name) and improve efficiency (up to 16x) to carry speech longer distances. The lack of a carrier can make voices sound funny (even a slight frequency error will cause a frequency shift) but for text there is no noticeable difference. Just 1-kW on an SSB radio can reach the equivalent range of a 4-kW AM or FM transmitter.
This technology has been around since the early 1900s. It was in service by the 1930s (lawsuits over patents delayed adoption) to connect a public radiotelephone circuit between New York (via Rocky Point listening station) and London (via Rugby listening station). After WWII the US Strategic Air Command adopted SSB as the standard for long-distance transmissions in its new fleet of B-52 aircraft .
LeMay became aware of the successes of amateur SSB work, and in 1956 undertook two flights, one to Okinawa and the other to Greenland, during which SSB was put to the test using Amateur Radio gear and hams themselves.
It thus makes sense for sailboats to carry SSB for their long journeys over open spaces. The protocol that we used on the boat with the radio to encapsulate and process our POP3 email was developed by SailMail.
The SailMail system implements an efficient email transfer protocol that is optimized for use over communications systems that have limited bandwidth and high latency. Satellite communications systems and SSB-Pactor terrestrial radio communications systems both have these characteristics. The SailMail email system’s custom protocol substantially reduces the number of link-turn-arounds and implements compression, virus filtering, spam filtering, and attachment filtering. The combination of the protocol, compression, and filtering dramatically improves communications efficiency.
Efficiency, efficiency…and point-to-point long distance communication. Does this remind you of another environment? Recently I have been reading about the challenges of communication in the revolutions in Ivory Coast, Bahrain, Saudi Arabia, Egypt, Libya…. The military, media or intelligence communities must be developing software for inexpensive USB SSB radios and laptops to stay in contact with groups inside those countries.
The Israelis have certainly documented various radio communication devices available to the Hizbullah including scanners and receivers set to monitor helicopter frequencies. Yet the Philippine government seems to suggest that SSB radios are difficult to obtain.
“However, the embassy cannot provide all the needed information [chassis number, model, etc.] since the post still does not have the radio transceiver units,” [Philippine Ambassador to Syria Wilfredo] Cuyugan said, emphasizing the need for the Foreign Affairs department to purchase at least one unit of HF SSB radio transceivers and five units of very high or ultra high frequency long range handheld radio transceivers.
The technology seems like a good fit. It may be less common than cell phones and consumer wireless or microwave options, yet some Tweets, email or other messages must now be escaping via SSB radio.
