What Is Winlink and How Does It Work?
History and Development of the Winlink Global Radio Email System
Winlink Global Radio Email, also known as the Winlink 2000 Network, is a worldwide radio messaging system built and administered by volunteers and financially supported by the Amateur Radio Safety Foundation (ARSFI). In July 2008, a developer named Rick Muething presented a new digital protocol at the ARRL/TAPR Digital Communications Conference in Chicago called WINMOR — Winlink Message Over Radio — which ran on a sound card. Before WINMOR, sending email over HF radio meant buying a PACTOR modem, a dedicated piece of hardware that cost over a thousand dollars. WINMOR opened HF digital communications to anyone with a computer, a radio, and a simple audio interface.
The system used to employ multiple central message servers around the world for redundancy, but in 2017–2018 it upgraded to Amazon Web Services, which provides a geographically-redundant cluster of virtual servers with dynamic load balancers and global content distribution. In November 2023, the FCC removed the symbol rate limit of 300 baud in favor of an occupied bandwidth limit of 2.8 kHz. In the Report and Order, the FCC stated that "the amateur radio community can and does play a vital role in emergency response communications, but is often unnecessarily hindered by the baud rate limitations in the rules." Supporting this change were a host of federal, state, and local emergency management agencies who continually wrote ex parte comments to the FCC regarding their concerns with the impact such a limitation had on emergency email communications via Winlink.
How Winlink Transmits Email Over RF Frequencies
You connect your ham radio to your computer or a specialized device, open the Winlink Express software, and type your message just like a regular email. Instead of hitting "send" through the internet, your message travels over the airwaves to a Winlink radio gateway somewhere in the world, which then forwards your message to the internet if available — ensuring it reaches its destination.
A store-and-forward format allows messages to be sent to an operator even if they are not on the radio at that moment, and text messaging has advantages over voice in certain situations, reducing errors when relaying important information such as numbers, technical information, and lists. In the To field, if you put an email-formatted address with an @ sign, the gateway will try to deliver it out of the Winlink system onto the internet. If you simply place a callsign, it will keep it in the system and try to deliver it to that ham when they next check for email on any node.
Key Components: RMS Gateways, Winlink Clients, and the CMS Network
The Winlink system has three primary components: (1) Common Message Servers (CMS), which form the Winlink backbone using Amazon Web Services in a redundant, fault-tolerant configuration; (2) Radio Message Servers (RMS), which act as the radio gateway between the client (end-user) and the Winlink system backbone; and (3) the Client system, comprising your radio, computer with Winlink software (Winlink Express), TNC (or sound card), and you, the end-user.
Remote Message Servers (RMS) are scattered throughout the world and are the RF connection into the Winlink system. RMS gateways access the resources of the CMS servers via the internet. These nodes are provided by hams familiar with the system and are set up on many ham bands (HF, VHF, UHF). Gateway Station Sysops support and run over a thousand stations around the world. They are essential for providing the radio network that allows us to use Winlink radio email. Without them, there is no Winlink.
Winlink vs Traditional Internet Email: Key Differences
Traditional internet email requires continuous, functional internet infrastructure. Winlink does not. The system is highly valued by amateur radio operators, emergency communicators, mariners, and remote expeditions for its ability to provide critical communication in areas without internet or cellular connectivity. Its ability to send emails over HF, coupled with internet integration, makes it an invaluable resource for maintaining communication in remote and disaster-impacted challenging environments.
Unlike conventional email, there is no expectation of privacy with the Winlink system. RMS gateway owners and Winlink administrators can read messages exchanged through the system, as they are looking for Part 97 violations and inappropriate usage. Message size is also constrained — PDF files can be large for Winlink use and easily exceed the 120KB limit. Additionally, all incoming and outgoing messages are archived online and viewable by all Winlink users via the internet for 21 days, and accounts off-air for 400 days are automatically purged.
Winlink Modes and Protocols Explained
Pactor: The Gold Standard for Winlink HF Connections
PACTOR is a set of standardized modes used by radio operators for FSK radioteletype transfer of digital information over shortwave bands. Effective radio-frequency communications over long distances over hostile radio paths require special attention to the rate at which data is repeated and error correction. To reduce the amount of data sent, on-line data compression is utilized along with memory ARQ error correction. PACTOR utilizes time-division duplexing for bidirectional, half-duplex communication.
Depending on the version of PACTOR protocol used and the radio-frequency conditions, PACTOR transmission speeds range from 20 to 5,200 bits per second net rate, or 9,000 bit/s gross rate utilizing speed 10 (32-QAM). Compared to other digital modes, PACTOR offers superior robustness and speed. Its adaptive modulation ensures a stable link where other protocols would fail, making PACTOR the first choice for mission-critical radio communication in professional and emergency networks.
Vara HF: The Popular Software Modem Alternative to Pactor
VARA HF, developed by José Alberto Nieto Ros (EA5HVK), delivers speeds comparable to PACTOR 3 using only a sound card. The software is shareware — free to use at reduced speed, with $69 USD unlocking full performance.
VARA is a software modem using orthogonal frequency-division multiplexing (OFDM) modulation. VARA is capable of HF speeds comparable with Pactor 3, achieving this using 52 carriers limited to 42 bps, thus satisfying the FCC symbol rate requirements. VARA uses a bandwidth of 2400 Hz. Performance testing confirms VARA's strengths: the much less expensive VARA HF did especially well across the range of conditions tested, and the SCS modems and VARA could run long test cases without losing a connection while ARDOP and WINMOR were slower and less reliable for lower SNR multipath cases.
Vara FM: Using Winlink Over VHF and UHF
VARA FM brings Winlink's capabilities to the VHF and UHF bands, making it accessible to Technician-class operators without an HF rig. VARA FM crushed AX.25/FX.25 VHF cases in side-by-side performance testing, making it the clear choice for FM-based Winlink operations. VARA is available for HF as well as FM and can be loaded and used from within Winlink Express. Simply select Vara Winlink or Vara FM Winlink from the Open Session menu in Winlink Express and follow the instructions to install it.
Winmor: Legacy Protocol and Current Status
WINMOR was the first accessible software-based HF modem for Winlink, but it has since been superseded by VARA HF. ARDOP exceeds WINMOR performance for strong signals but both ARDOP and WINMOR have performance a small fraction of the speed of the other modes. The HF modem technologies currently in use include PACTOR, Winmor (deprecated), ARDOP, Vara HF, and Automatic Link Establishment (ALE). New operators should install VARA HF rather than relying on WINMOR for any serious operations.
Packet Radio (AX.25) and Winlink on VHF Bands
VHF/UHF protocols include AX.25 Packet and Vara FM. Two-meter packet typically uses the 1200 baud rate on frequencies such as 144.93, 145.01, 145.03, 145.05, 145.07, 145.09, and 145.53 MHz. AX.25 packet gateways are widely deployed and require nothing more than a TNC or software-defined modem like Direwolf or UZ7HO Soundmodem. While VARA FM is faster and increasingly preferred, AX.25 packet remains a dependable fallback in areas where VARA FM gateways are not yet established.
Getting Started with Winlink: Hardware Requirements
Choosing a Radio for Winlink HF Operations
An HF transceiver — any SSB-capable radio — is sufficient for Winlink HF. Many modern rigs have built-in USB sound card interfaces. Sound card interface options such as SignaLink, Tigertronics, or similar accessories are available. Some radios, including the Icom IC-7300 and Yaesu FT-991A, connect directly via USB. Radios with built-in USB audio and CAT control eliminate the need for a separate audio interface box, simplifying setup considerably.
For VARA FM and VHF packet operations, any 2-meter or 70-centimeter FM transceiver works. The Kenwood TM-V71A, Yaesu FT-7900R, and entry-level handhelds all connect to a computer using a simple audio cable and VOX-based or CAT-controlled PTT interface.
TNC Options: Hardware vs Software-Based Modems
Winlink requires a TNC or Terminal Node Controller. There are two methods — software or hardware. Perhaps your radio has a TNC built in. Most operators will likely use software. Andrei Kopanchuk UZ7HO provides a free software TNC called soundmodem for packet operations. For VARA modes, the VARA application itself serves as the modem, communicating audio to and from your radio through a sound card interface.
PACTOR Modem Options: SCS and Other Manufacturers
The SCS PXdragon DR-9400 is a modern, high-performance PACTOR modem for reliable data links in amateur radio. It supports PACTOR-1/-2/-3/-4, Packet Radio (1k2 AFSK / 9k6 G3RUH) as well as Robust Packet Radio (RPR), and adds useful receive modes such as weather-fax (RX) and RTTY (RX). With PACTOR-4, data rates up to 10,500 bps can be achieved — significantly faster than Robust Packet or ARDOP.
SCS hardware modems represent the pinnacle of HF Winlink performance and are the choice of serious EmComm operators, mariners, and expeditioners who need guaranteed link reliability regardless of band conditions. However, the high cost of SCS modems (typically over $1,000 USD) means most new operators start with VARA HF instead.
Budget-Friendly Setups for New Winlink Operators
Most newcomers start with VARA HF because it offers the best balance of speed, cost, and ease of setup. A budget Winlink HF station can be assembled for well under $500 USD using:
- A used HF transceiver such as the Yaesu FT-450D or Kenwood TS-480
- A SignaLink USB or similar USB audio interface ($120–$150)
- A licensed copy of VARA HF ($69)
- Winlink Express (free)
- A simple dipole or end-fed antenna
Winlink Express is compatible with Microsoft-supported 32- or 64-bit Windows OS, including Windows 7, 8, 10, and 11. It can also be used on Apple Mac and Linux machines using a virtual machine engine or dual boot setup. Older operating systems like Windows XP are not supported. The program has minimal CPU demands but may require a computer with at least 700 MHz Pentium/Celeron class and 2 GB of memory for modes using sound card modems.
Winlink Software Setup and Configuration
Downloading and Installing Winlink Express
Winlink Express is an email client program used to send and receive email
