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WorldEmail at SeaModem


In order to send and receive email, your computer needs to send and receive a series of ones and zeros. This is called "digital data" and can be used to encode emails, GRIB files, pictures, etc -- basically any piece of data that your computer can handle all comes down to ones and zeros.

Propagating through the atmosphere, travelling through wires, and in many other places, there are electrical waves of various types. These are often "analog signals", for example music or voices that you hear, HF radio signals, satellite radio signals, etc, are all examples of analog signals.

A modem (short for "modulator-demodulator") is any kind of device that converts digital signals to and from analog signals. Modems allow your computer to talk to other computers over long distances. Even when you think that there are digital signals travelling directly to and from your computer (e.g. ethernet, wi-fi), these are in fact all modulated over analog waves travelling through wires or through the air (or through space).

Different types of modems are relevant at sea, but the main ones are:

  • Pactor HF radio modems
  • Satellite phones

Note that other types of modems exist -- the old style telephone modems, ADSL modems, etc, but these are outside of the scope of this article.

We don't normally refer to a satellite phone as a modem, but in fact all satellite phones are capable of operating as modems for sending digital data as well as making regular voice calls.

HF Pactor Modems



A number of specialist marine electronics stores sell the PACTOR modems, a sample are as follows:

Installation and Setup Details

Things you will need:

  • An HF Radio of a specific type.
  • A PACTOR modem.
  • A computer running Microsoft Windows
  • An account with a service provider such as SailMail
  • Free software called AirMail3.

In order to use a Pactor modem, one of a few different types of HF Radio are required. Generally speaking these are:

  • ICOM M710
  • ICOM M801E
  • ICOM M802

Older ICOM models such as the M600 can sometimes be made to work using a special type of adapter that needs to be patched into the internals of the radio, however last reports were that this adapter was no longer available for the M600.

Step by step installation guide


Also see the Email at Sea page.

Satellite Modems

Although dedicated satellite modems (data-only devices) are available for use at sea, for the average sailor a satellite phone and connection kit is what is required. For all further details see the satphone page.

Software Modems

We don't normally refer to a piece of software as a modem, but in the case of WINMOR, the software does exactly what a modem does -- converting the ones and zeros inside your computer to and from analog audio signals in your PC mic/speaker jacks. These audio signals are then converted to HF radio signals by the HF Radio itself, just as if you were talking by voice over the radio. For more details on how this works see the WINMOR page.


Publications, etc.


List links to discussion threads on partnering forums. (see link for requirements).



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  • (from GoneTroppo): I use my HF connected to a Pactor IIpro and the HAM version of Airmail on Ham frequencies with my Ham callsign. HF & Pactor is only one method to connect to Ham gateways, WINMOR is another (no modem). There are many Ham gateways around the world and they vary in the amount of time one can use them for per day. Some are as little as 30 minutes/day and some have no time limit. A HF and a Pactor is definately a way to connect to Winlink. Only ever used Sailmail crossing N Pacific in 2005. With bad reception receiving a Grib a day used up our weeks time in a few days. We then received a notice saying we had used more than our time and we would be denied access for a few days, cannot remember the exact number. From then on we kept checking connection speed and if it was slow we logged off quickly, and kept testing reception that way. No probs after that.

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Names: Delatbabel

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