Winlink 2000 – a worldwide system for sending and receiving e-mail over radio without the Internet

Since this system does not rely on the Internet it is widely used by mariners, RV campers, missionaries, and various agencies who need to communicate when the Internet is not available at the last mile location.

The Winlink system consists of a group of Common Message Servers (CMS) placed at various locations around the world. These servers connect via the Internet to Radio Message Servers (RMS) in many geographic locations to form a star network configuration. The Radio Message Servers are the UHF, VHF, or HF RF gateways into the Winlink system. The final component on either side is a client computing device running the software to send/receive messages through your radio. In Internet terms, you could think of the Radio as a modem (very loosely speaking).

The client computer will generally run Winlink Express if it’s a Windows computer, or AirMail if a MacOS (Airmail can also run under WINE or CrossOver on Linux). Yes, Pat and Paclink will run on Linux but it is a bit dismal to try setup and use. Winlink is very skewed towards Windows users which is a great pity. A newer open source alternative, called Paclink, is being built with a view to it being more cross-platform.

The client software will also connect via Telnet over the Internet so if your Internet links are up you can use it is in this way. If the Internet is not available your radio would need to establish a connection to a RMS via radio frequency (RF). Here in South Africa, there are a few RMS’s in the major cities, with VHF Packet mode radio in Cape Town, but if I wanted to try to reach Gauteng’s RMS I’d need to go HF (which means it may not be available 24/7 to me due to RF propagation). You’d also need to take into account what type of digital mode is supported by the RMS eg. the one in Cape Town is Pactor and VARA HF so anything else won’t connect to it on HF. The Cape Town Packet mode on VHF is on frequency 144.575 MHz.

No 2m Winlink connectivity, try APRS digipeaters instead

Regarding connectivity and modes, and interesting feature of APRS digipeaters, is that they will retransmit any Packet mode transmission. So if two Winlink stations were to both use Packet mode (eg. on FM), and instead switch to 144.800 MHz for APRS, they can digipeat via the APRS digipeater to communicate on Winlink in Packet mode. This is of tremendous benefit during tactical deployments were a voice, or APRS message, is sent to switch Winlink stations to the APRS digipeater frequency for better coverage. It will obviously make your APRS channel a lot busier so that needs to be considered. Also consider that if the Winlink server stays on say 144.575 MHz then it is not hearing anything via the APRS digipeater, so the server side (or other client peer) also needs to change to the APRS frequency.

The screenshot below shows a Packet Winlink connection screen, with a connection destined to ZS1SJ-10 via an APRS digipeater called ZS0DCC (my station and remote station’s radios tuned to the APRS digipeater frequency instead of normal Winlink frequency):

Winlink Digipeating
Winlink uisng an APRS digipeater

Winlink e-mail address

A registered user would receive a [email protected] e-mail address for the system. Anyone could then send via the Internet (from Gmail or any other e-mail address) to that e-mail address. Bear in mind there are stringent anti-spam measures in place for inboard e-mails, as well as message size restrictions. Normally replying to a Winlink message should not be a problem, but if initiating from outside of Winlink, the recipient has to either have whitelisted the sender address, or a temporary anti-spam bypass needs to be added to the subject line by the sender.

A mariner for example at sea would have their radio and computer running and trying to auto-connect say every 10 minutes. In the short period that the radio manages to establish the connection, that mariner would receive waiting e-mails, weather reports, and send any mail they had composed ready for sending. It works in a store-and-forward mode.

It is also possible to make direct peer-to-peer connections between two client computers (radio stations) that are within radio range of each other (could be 30km or 500km). This could also allow a radio station with only VHF/UHF capability to connect to another station with VHF/UHF and the second station could forward the messages into the Winlink system using HF.

If using amateur radio bands the usual restrictions apply and a license is required. But one can see how useful this can be during a disaster as a lot more accurate communication can be exchanged more quickly than during it using phone mode (voice).

There is a lot more detail in the beginner’s guide at and the Winlink site at

Equipment Needed for Winlink

Equipment can vary from very cheap through to very expensive. If will really depend on what modes you need to connect on, and what radios your have. Unlike APRS which has mobile apps, Winlink does at the very least require a computer of some sort to run the Winlink Express software, or a Raspberry Pi (such as DigiPi) if you were to use the Pat software. On the highest end you’d end up using an expensive Pactor modem for long distance over HF.

So it is easier to work around what radio you have, as that really determines what your options are:

General Handy’s, Portables and Mobile: Can use audio cable connectors to a DigiPi (on a Raspberry Pi which can use Pat instead of Winlink, with ARDOP as it’s mode), DigiRig, Mobilink TNC, SignaLink, TinyTrack4, TNC-X, Kantronics KPC-3, or similar, which works to a computer. These manage sound through the radio’s microphone and speakers. The audio cable and plugs are very dependent on the specific radio. These should work fine for Packet mode operation, or with modes such as VARA FM or ARDOP. So this setup could consist of:
* Android/iPhone with APRS apps (or Android can also run WoAD Winlink app)
* Audio cable
* TNC such as Mobilink, DigiRig, TinyTrack 4, etc
* Handy radio such as Yaesu FT-60R, Baofeng, etc that has audio/mic sockets.

Kenwood D72, Kenwood D710, or similar radio with a built-in TNC: Only requires the computer connection cable. Winlink would communicate via a KISS port interface (provided by the TNC). Again fine for Packet mode.

Yaeasu FT-991A, Icom 8100, or similar radios with a built-in soundcard and USB connection: Usually just the USB cable to a laptop or computer, and it often requires software like SoundModem to be running for the packet modulation if Packet is being used, or the VARA FM software if VARA is to be used. Modes such as ARDOP are driven directly from the Winlink Express software.

For the HF Pactor modes, a SCS modem is required, which can be pretty expensive, but of course also very efficient.

But the best advice is to start off by seeing what Winlink stations are nearby that you want to connect to (see, and check what frequency and mode they are working on. Then determine from that what is needed to use that mode (software only or also a hardware device), and then the frequency will determine if you a radio for that frequency and distance.

Usually if you do an Internet search for your radio model and “winlink”, you should find a guide more specific to getting your particular radio connected.