VHF, SSB, AIS and Satelite Communication

Plans are to replace all of the original communication equipment, except perhaps the marine VHF. A VHF with ability to send and receive and display non-distress DSC may be purchased. AIS will be installed. Satellite communication will include Iridium Go, possibly Garmin inReach, and possibly Space-X Starlink. There are no plans to install SSB or carry EPIRB.

Background

Just as technology has evolved in navigation, it has evolved in communications, perhaps even more so. Loran and radio direction finders (RDF) are a thing of the past and GPS, introduced in the 1980s is now the dominant means of finding position. In communication reliance on marine single sideband radio (SSB) is fading and newer technologies are beginning to replace emergency position indicating radio beacons (EPIRB). The marine VHF radio (very high frequency) remains by far the short range communications method of choice, though augmented with digital selective calling (DSC) and automatic identification system (AIS). The most dramatic changes in marine communication are the advances in satellite communication and it's improving affordability.

Marine VHF

Marine VHF is universal and is a necessity to enter foreign harbors. The allocation of channels varies somewhat around the globe as well as level of formality. Some countries require ships to identify by their call signs. In the US call signs are allocated for free by the FCC with renewals every 10 years. The FCC also issues MMSI numbers (maritime mobile service identity) used by VHF DSC. VHF radios have at least two transmit power settings, low and high. For handheld radios low is usually 1W and high is 5W. For fixed mount radios low is usually 5W and high is 25W. Special licence is required to transmit over 25W and is usually limited to ground stations, such as the US Coast Guard stations. The range is limited to 1-2 miles for 1W, 5 miles for 5W, and 25 miles for 25W. The curvature of the earth limits low antenna, such as between small powerboats, to about 15 miles and small sailboats to about 20 miles. The very tall USCG towers, high power transmit, and highly sensitive receivers make range to USCG stations as high as 50-100 miles, limited again by curvature of the earth.

Marine VHF DSC

DSC uses VHF channel 70 to send digital messages. All fixed mount VHF radios today have a SOS or distress call button, which if pressed transmit a distress signal with position (if available) and MMSI. There are five DSC priorities: distress, urgency, safety, routine and test. Some newer fixed mount VHF radios can transmit and display digital non-distress messages over DSC. All marine VHF radios must have the minimal distress signal capability though registering and programming a MMSI number is up to the boater and few do so. Without a MMSI number and without position information from a GPS the call becomes a distress from an unknown vessel at unknown location (except 25 miles from where it was received). Large commercial vessels are required to have more advanced DSC capability. Despite these requirements, due to budget constraints no USCG station had DSC capability until 2015. Now seven USCG stations have DSC. DSC is also available on numerous HF (SSB and HAM) frequencies but is not mandated.

Marine SSB and HAM

Marine SSB and HAM (amature radio) had in the past been the only means of long distance communication. These both use MF and HF (medium frequency and high frequency) bands which are reflected back to earth by the upper atmosphere and therefore can travel very long distances, and sometimes depending on atmospheric conditions around the globe. There is much less reliance on SSB and HAM these days as satellite communications is far superior and has become affordable.

Marine AIS

Automatic identification system (AIS) is used for collision avoidance. AIS uses VHF channels 87 and 88. AIS information is periodically transmitted. Typical period is 2-10 seconds for rapidly changing information and 6 minutes for static information. To conserve power on small vessels the transmit period can be increased, typically to 1-2 minutes and is often done on the open ocean. AIS is required on large vessels. Small vessels sometimes have AIS receivers but are better served by having an AIS transceiver. The AIS transmitter is separate from the VHF radio transmitter but can share the same antenna. Most AIS transceivers have a built in splitter which prevents the transmit power of one device from reaching the receiver of the other (and potentially damaging the receiver).

AIS transmits MMSI, vessel position, heading, course, speed, UTC time, and other information. All chartplotters sold today support display of AIS information as well as warnings of potential collision courses or projected pass in close proximaty.

AIS messages are organized into 1 minute frames. There are a total of 2250 time slots per VHF channel and two channels so 4500 available time slots. In busy shipping areas the transmission of a message every 2-10 seconds can congest the available bandwidth. Transmission period can be lengthenned if congestion is detected. To avoid congestion transmit power is limited to 2W which limits range to 5-10 miles, though in the radio quiet of the open ocean AIS signals may appear from vessels 15 miles away or more.

EPIRB

Emergency position indicating radio beacon (EPIRB) is intended to be transmitted in distress conditions far from shore. EPIRB is received by satellite and relayed to international coast guard authorities. The original EPIRB used 121.5 MHz and relied on the satellite to identify the approximate location of the distress signal, accurate to within 20 km at best. The newer 406 MHz EPIRB is accurate to 2km.

More recent 406 MHz EPIRB are capable of transmitting GPS coordinates. EPIRB have built in batteries with a lifespan of 10 years. When activated an EPIRB will transmit every 50 seconds, but will usually run out of battery power within 48 hours.

The USCG receives far too many accidental EPIRB activations. For this reason, USCG will fail to respond promptly to any EPIRB activation unless contacted by other means, more so if the activation occurs in international waters. The other means of contact was often friends or relatives notifying of a vessels failure to arrive at port, which may be days or weeks later. Since the EPIRB battery has long ago died, the search area can become very wide with rescue further delayed. Coast guards at other countries can be much worse, failing to respond at all.

Due to the failings of EPIRB, it may be past the system's useful lifespan. Other much better means of providing distress information are available via other satellite communications, though with a monetary cost.

Satellite Communications and Internet

Satellite communication has been available for almost a half century but had been impractical until the last decade or two. The early marine satellite equipment was very large and extremely expensive domes and equally costly subscriptions for very little bandwidth. Not only was the cost prohitable, but the size of the domes made it impractical to put on even larger sailing vessels. This has changed.

Viasat was among the earlier satellite services to lower price and reduce the size of the domes. Iridium, a long time supplier of satellite phones and subscriptions, introduced their Iridium Go product line, supporting calls, texts, and email at an even more reasonable price. Viasat is no longer cost competitive.

Iridium Go

The Iridium Go is a small unit in the cabin with a small external antenna usually mounted on the mast. Iridium Go supports WiFi to allow any cell phone or tablet. By itself Iridium Go supports only voice, SMS text, GPS, and SOS. A service from PredictWind bundled with Iridium Go supports GRIB files with weather, ocean conditions, and provides weather routing and other capabilities such as AIS satellite data. The PredictWind offshort app is available on IOS, Android, PC and Macintosh computers. There is no support for Linux or FreeBSD. PredictWind also supports an email service for an added cost. The optional PredictWind DataHub provides very accurate GPS tracking even when offline (stored locally) plus AIS data upload and download and integration with NMEA-2000. With the Pro subscription (expensive) AIS range can be expanded from under 20 nm to 300 nm using satellite AIS data.

Garmin inReach

Garmin offers their inReach service. InReach devices can use WiFi or the Iridium satellite service. These devices support unlimited two way communications with other inReach devices on all but their lowest cost service ($7.99/month "Enabled" service). The inReach SOS service allows 2-way communication with Garmin staff serving as an emergency dispatcher and is available on all services, including the lowest cost service. All but the lowest cost service bundles a small number of text messages and even smaller number of voice messages or photos per month (on devices that support this) for a low cost or a higher limit for a higher monthly cost. The $14.99/month service ("Essential" service) offers 50 SMS text messages or weather requests per month. The inReach

The Garmin inReach is somewhat redundant if Iridium Go is used. The additional cost, though low, is hard to justify. Garmin inReach might be a useful addition to Iridium Go for communications when off the boat, such as in the dinghy or scuba diving. It might also be good for crew to crew communication when one or more crew member is off the boat. This is not applicable is single handing.

Terrestial WiFi

In populated areas some businesses offer WiFi, usually with reasonable bandwidth. This provides one means of casual web browsing as well as being capable of supporting most data uploads.

Cellular Data

Outside the US cellular service can be very inexpensive, though the effective data rates can be quite limited. The Saily service offers short term eSIM downloads in 121 countries, saving the trouble of finding a SIM card and finding the lowest cost offerings in each country. Plans are available in 7-day and 30-day durations and with 1GB of cellular data and up.

Cellular service is limited to on land in populated areas or very close to land such as anchored near a populated area. Very remote or uninhabited places will have no cellular service and there is no cellular service offshore.

Cellular data is limited. Many high resolution photos are 5MB to 10MB in size. Even relatively short high resolution videos can be multiple GB in size. Cellular data may be adequate for uploading full resolution photos but not adequate for uploading full resolution video. Cellular data is certainly adequate for casual web browsing.

Space-X Starlink

The Starlink Roaming global service with standard antenna provides relatively high Internet access speed, at 5-50 Mb/s. The subscription cost is high but can be enabled or disabled on a month by month basis. The cost is $250/month plus $1/GB of data. Starlink has a few downsides besides the cost. The antenna is not very waterproof at IP56 rating. Coverage is about 90% global. While Iridium Go consumes 5W, Starlink consumes 90W. The Starlink connection will be disrupted when it rains.

Whether to install Starlink depends on whether there will be a need to access the Internet when offshore or if high speed data is needed.

VPN and IPv6 capability

A VPN provides two primary capabilities. The apparent location of the client can be hidden since any application server, including web servers or web hosting sites, see an address of the VPN server. The second capability is related to privacy, randomizing client addresses to thwart attempts at tracking. I am only interested in the first capability since some sites, such as banking and brokerage will block addresses from many countries.

Currently I have two servers colocated at data centers. For situations where IPv6 is not available an ssh based tunnel to one of these servers is used. A side effect is this provides location hiding for IPv6 which could be useful when in another country. It might also be possible to tunnel IPv4 using the same tunnel. The client would then have two IPv4 addresses. It would be necessary to route the IPv4 for the tunnel itself (preferably the entire subnet containing the colocated server) to the provider address and create a default route to the tunnel to any other IPv4 address. Currently the colocated servers don't have spare IPv4 addresses (and don't use NAT), but there is a shared IPv4 address used for system recompiles that can be shared with the VPN server as well.

The tunnel exists on the host rather than a router and since there is no NAT supports only one device at a time. A client side router with NAT could be used along with a separate IPv6 /64 prefix if the colocation provider is willing to provide another IPv6 prefix.

This tunneling capability will be needed for terrestial WiFi, cellular data and possibly needed with Starlink.

New Communications Equipment

The prior Background section provides the reasoning for the choices of communication equipment that will be used and communication equipment that will not be carried onboard.

A marine VHF is essential. The existing VHF is adequate but the ability to send and receive non-distress DSC messages would be a useful addition so the VHF may be replaced.

Neither marine SSB or HAM radio will be installed.

An AIS class B transceiver will be installed with an integral antenna splitter to share the antenna with the VHF radio.

An EPIRB will not be carried aboard. The Iridium Go or Garmin inReach provide superior long distance distress capability, though both require a monthly subscription.

The PredictWind service with an Iridium Go will be the primary means of downloading weather, sea conditions, and weather routing as well as uploading position. The PredictWind DataHub will be purchased. The PredictWind "Standard" service will be used, which can be billed at $99 per 3 months or $249 per year. The yearly billing will be used after shakedown sails are completed.

The Garmin inReach offers incremental improvement over Iridium Go alone and may be purchased. The $7.99/month or $14.99/month ($95.88 or $179.88 per year) is a steep price but can be added or dropped on a per month basis. A Garmin inReach might be purchased though it seems unlikely.

A cell phone will be carried onboard with no configured cell phone service. A Saily account will be created. Saily eSIM downloads will be activated as needed.

Initially Starlink will not be installed but Starlink will be added if needed with the Starlink subscription enabled only as needed due to the high cost.

Tracking and periodic updates will be provided via Iridium Go. Any need to upload data will wait until Internet over WiFi is available somewhere. Limited uploads will be provided over cellular data as well as casual web browsing. Starlink will be purchased and the subscription activated as needed if terrestial WiFi and cellular data prove inadequate.