Email at Sea

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WorldEmail at Sea

You can actually get email while underway? Of course! Utilizing either your HF Radio or a satellite system you can send and receive email right from your boat. There is some specialized equipment needed to connect up, however, and below we'll talk more about that.


  • To send and receive short text emails while at sea (out of sight of land, out of range of 3G/4G/WiFi coverage).
  • To send requests for and receive GRIB data files containing weather information, or other weather data, to assist in passage planning.

Note that there are higher bandwidth satellite systems which allow full internet access at sea, from anything up to fast dial-up/ISDN speeds (around 64K-128Kbit/sec) up to 1MBit/sec or more. These systems are currently outside of the scope of this article because they tend to be expensive, at least outside of the budget of most cruising sailors. Foir more information on those systems see Satellite Broadband.

Problems and Solutions

There are a number of issues with accessing internet style email and web access while at sea. This is mostly due to the low bandwidth and high latency of a typical data connection running over HF Radio or a satphone.

  • Bandwidth represents the amount of data that can be sent over the connection during a certain period of time, usually measured in bits per second (or some multiple of bits). A typical home ADSL connection, available in most countries, will have a bandwidth of between 1 and 10 megabits (10 million bits) per second, whereas a HF Radio or satphone connection will have a bandwidth of between 1 and 5 kilobits (1000 - 5000 bits) per second. The average email message transfer is around 80,000 bits, which means although it takes under a second to transfer this sort of message at home, it might take several seconds or longer to transfer while at sea. Photos added as attachments to emails can increase that message size up to 10 or 50 million bits, so it might take a very long time to transfer while at sea.
  • Latency represents the turn-around time between one end and the other end of a network connection. A typical home internet connection might have a latency of around 50 milliseconds (50/1000ths of a second), whereas a satellite or HF Radio link might have a latency of 2 or 3 seconds.

Having such a low bandwidth and high latency means that the following problems will arise:

  • Large messages take very long to download, and since the cost of remaining connected via HF or satellite is high (or there might be limits on the amount of time during which you can remain connected), the cost of downloading mail messages becomes very high or unsustainable.
  • Due to the high latency, most mail clients will time out while waiting to receive a connection from the other end over HF or satellite. This represents the mail client thinking that the connection has disappeared or become disconnected, whereas it is simply a matter of waiting for longer for each network packet.

The basic solutions to these problems involve using special software and/or servers, which can perform the following tasks:

  • Compress messages, often to a high degree of compression, between the mail server hosting the mail (on land) and the ship (at sea). This requires co-operation between the mail software and the mail server, as they must agree on the compression protocol to be used and the level of compression to be used, so that each side understands the other side.
  • Filter out large messages, discarding them at the server side (or blocking them until a higher bandwidth connection is available) to prevent the mail connection becoming choked with messages that are too large to be downloaded.
  • Acting as a local mail server so that each message doesn't have to be sent and received by the mail software connecting to the mail server -- a separate mailbox is kept on the ship board computer, and synchronised with the mail server on land only when the connection is available. Some mail programs (e.g. XGate) will automatically start the connection, synchronise all mail needing to be sent, and then close the connection immediately, thus preserving precious or expensive connection time.

It is often the case that the software is relatively interchangeable regardless of the connection method. For example, although it's often thought that sailmail is primarily for ships using HF Radio to connect, and XGate is primarily for ships using a satphone, it is in fact the case that either sailmail or XGate will work for either HF Radio or satphone.

Internet or Not Internet

Typically when you are reading email at home you are connected to the world-wide internet. This is a network that can do many things -- email, web browsing, facebook, twitter, and provide other types of connections, e.g. for applications that run on smartphones.

One significant difference between most HF Radio connections and a satphone connection is that an HF Radio connection typically (e.g. via PACTOR or WINMOR) does not connect your ship directly to the internet. Instead it connects to a separate network of HF Radio stations, over which some internet traffic can be gated -- in particular, your email can be delivered. It's still a data network, but it uses a different set of data protocols from the rest of the internet and can't be used for normal web browsing.

A satphone connection typically connects your ship to the internet in such a way that any normal internet activity is possible -- not only fetching mail but also web browsing, facebook, twitter, etc. Of course it's a very high latency and low bandwidth connection and so without special software (proxy software with compression), actually doing any web browsing will be an exercise in frustration, but it is still technically possible.

There are pros and cons of this. Obviously once you have an internet connection then with the right software anything that's possible on the internet should in theory be possible on board. However the internet data protocols are not very well optimised for high latency and low bandwidth connections, and so most of the things that you would do on the internet are going to be extremely difficult (or impossible due to timeouts) over a satphone. Because the protocols like PACTOR and WINMOR, as used over HF Radio are specially designed for low bandwidth links, they are potentially more suitable for shipboard use. However the limitation is there that it's suitable for only those things that were planned for by the designers of the protocols -- in both cases that is just email.


There are 3 basic options that are able to perform low bandwidth email while at sea. These are:


If your primary goal is to receive weather data and only weather data, then there are two options which don't incur some of the costs of these methods for getting weather data:

  • Weatherfax -- using just an HF Radio, a PC soundcard and some software, basic weather information can be received.
  • NAVTEX -- this provides text format weather data over an MF frequency, some HF/MF radios can be tuned to this frequency although it is more common to purchase a dedicated NAVTEX receiver.

Satellite Broadband services are starting to get cheaper each year, but the equipment cost is still very high.

Equipment Required, and Pros & Cons

There are two different systems which can be used to access email over HF Radio. The more common one of these is the PACTOR system which connects via a Modem, and generally uses the Sailmail system. The other is the Winlink system (Winlink 2000 to be more precise). These use different HF Radio gateways -- the Sailmail system has a set of PACTOR stations worldwide which operate over the marine HF bands. The Winlink system also has a set of HF stations, some of which use the PACTOR modem and some of which use the WINMOR protocol which operates without a modem. In either case, the Winlink stations operate on the Ham Radio bands and so you need a Ham Radio license in order to use them.

HF PACTOR system


This relies on having a specific type of modem to connect to one of a range of models of HF radio.

Pros and Cons:

  • + Operating costs are low, no "call time" purchases are required.
    • Using the sailmail system costs $250 per year.
  • + Since an HF Radio will be part of standard equipment for most cruising sailors, this method re-uses equipment that may already exist on board.
  • - An HF Radio of a specific make and model is required, most earlier model HF and SSB radios don't support the connections required for the Modem.
  • - The specific type of Modem that is required is expensive.
    • Indicative cost for the modem is US$1148 for the Pactor-III modem or $1498 for the faster Pactor-4 modem, as of February 2014.
    • This doesn't include the cost of the HF Radio which could be around $2500 for the radio and tuner, but I would suggest that these are required equipment on a sea-going vessel anyway, even if they are not used for email.
  • - The system is not cross-platform, it requires some software which only runs under Microsoft Windows.
  • - There is a 90 minute per week connect time limit for using the sailmail (airmail) software. This software is required to fetch email via HF because the HF/PACTOR system doesn't provide a true IP connection, only a limited / proprietary protocol connection over which the sailmail system and airmail software will run. This can be an issue in areas of poor coverage, the sailmail web site suggests using a Pactor-III or better modem to alleviate this issue.


Pros and Cons:

  • + Operating costs are low, no "call time" purchases are required.
  • + Since an HF Radio will be part of standard equipment for most cruising sailors, this method re-uses equipment that may already exist on board.
  • + Most HF Radio types will work, the specific type with modem connections is not required.
  • + A Modem is not required, this uses software on the PC to emulate the modem.
  • - A HAM (amateur radio) license is required. If you have a standard maritime HF license then you are not allowed to use this system because it uses frequencies in the HAM bands and not frequencies in the Marine HF bands.
  • - The software is not cross-platform, it requires Microsoft Windows.

Satellite system

Iridium 9575 Extreme Satellite Phone

Pros and Cons:

  • + The hardware cost of the satellite phone is lower than the cost of the HF radio and Modem, in case an HF radio (or the specific type of HF radio) is not already installed.
    • Indicative price for satellite phones is US$980 for the Iridium 9555 or US$1230 for the more advanced Iridium 9575 as of February 2014.
  • + The system is easy to set up and cross-platform.
  • - Purchase of call time "minutes" are required.
    • Indicative price of 500 minutes is US$675 as of February 2014.
  • + The system provides a true IP connection to the internet, although it is rather slow. In theory it's possible to do anything over that connection that can be done over a normal internet connection.
    • - Additional software and/or service subscription may be required to make effective use of email over the slow IP connection provided by the satellite. Typical plans are about US$30 per month for an XGate subscription as of February 2014.

Set Up for Email


This is covered in Setting a PACTOR Modem up for Email


This is covered in Setting a Satellite Phone up for Email.



Weather Data

GRIB files

GRIB files contain information about predicted wind speed, wave height, etc, for a region over a period of time. They can be loaded into stand-alone GRIB viewing programs such as GRIB Explorer for Windows, or loaded into navigation software such as OpenCPN which allows you to overlay the GRIB data onto your chart/ship position data.

Generally speaking, GRIB files are requested and received as attachments via email, and so you need one of the methods described here to send and receive emails. There are several services that provide GRIB files:

  • GMN provides free GRIB data via an email robot.
  • Saildocs provides an email based GRIB request service.
  • PredictWind provides a premium high-resolution service out of New Zealand.


Weatherfax data doesn't come in the form of digital files that you receive via email, it is directly transmitted over an HF Radio frequency. More information is on the weatherfax page.

Service Providers


Commercial stations provide services over marine HF/MF Radio frequencies. Because users hold a marine license they may communicate from any territorial or international waters. Messages can be encrypted and can contain any type of information.

  • Sailmail The SailMail Association is a non-profit association of yacht owners that operates and maintains an email communications system for use by its members. SailMail email can be transferred via SailMail's own world-wide network of SSB-Pactor radio stations, or via satellite (Iridium, Inmarsat, Globalstar) or any other method of internet access. (Sailmail Association)
  • ShipCom LLC provides email, fax, telegram, and phone patch capabilities from several shore stations around the United States including coverage in the Atlantic Ocean, Caribbean Sea, Gulf of Mexico, Pacific Ocean, and Bering Sea using WLO and KLB radio stations.
  • BBRemail Brunei Bay Radio provides a Pactor/Airmail based HF/SSB radio email service from its central South East Asian location on the north-west coast of Borneo, in an approximately 3000nm radius. (See the General section below)


E-mail services utilizing amateur radio frequency spectrum cannot be used for commercial purposes. If you plan on communicating any business-related information you should utilize a commercial service provider as these types of messages are not allowed on amateur radio. Also, you should be aware of transmitting from territorial waters of foreign countries as most have restrictions on third-party traffic and whether or not they accept your foreign amateur radio license.

  • Winlink is a service for amateur radio operators to send and receive e-mail messages from anywhere on the globe.
  • Winmor replaces the expensive Terminal Node Controller (TNC) usually required with a relatively cheap sound card and software.


See Satellite Service Providers


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