WSJT-X is a computer program used for weak-signal radio communication between amateur radio operators. The program was initially written by Joe Taylor, K1JT, but is now open source and is developed by a small team. The digital signal processing techniques in WSJT-X make it substantially easier for amateur radio operators to employ exotic propagation modes, such as high-speed meteor scatter and moonbounce.^[2] Additionally WSJT is able to send signal reports to spotting networks such as PSK Reporter.^[2]

WSJT, the predecessor to WSJT-X, was originally released in 2001 and has undergone several major revisions. Communication modes have been both added and removed from the software over the course of its development. Since 2005, the software has been released as open source software under the GNU General Public License. This licensing change required substantial rewrites and took several months to complete. Although Joe Taylor was the original developer (and still acts as maintainer), several programmers are currently involved in writing the software. The latest version of WSJT (not to be confused with WSJT-X) is written in Python and C, with several utilities written in Fortran.^[3]

WSJT versions up through 7.06 r1933 (referred to as colloquially as WSJT7) and earlier were aggregations of previous versions, and as such WSJT7 contained 16 different modes (FSK441, JT6M, JT65 variants A - C, JT2, JT4 variants A - G, WSPR, and a preview of JT64A). As of version 8.0 (referred to as colloquially as WSJT8) the available modes changed completely such that WSJT8 now offers 5 different modes (JTMS, ISCAT, JT64A, JT8, and Echo) - none of which are back-compatible with WSJT7 or earlier releases.^[4] This backwards-incompatibility includes JT64A, such that the preview release of JT64A in WSJT7 cannot communicate with the stable release of JT64A in WSJT8. As of May 2018, the latest WSJT version is WSJT10.

The software carries a general emphasis on weak-signal operation and advanced DSP techniques; however, the communication modes rely upon different ionospheric propagation modes and may be used on many different bands.^[5]

WSJT's communication modes can be divided into fast and slow modes. While fast modes send character-by-character without error correction, the slow modes aim to optimize for minimal QRO (high-power) use. As of WSJT10, supported fast modes are JTMS, FSK441, ISCAT, and JT6M, and the slow modes are JT65 and JT4.^[2] WSJT-X 1.8 additionally implements the "slow" JT9, FT8, and QRA64. Some modes have derived submodes with larger tone spacing.^[2] Two other modes, WSPR and Echo are included for measuring propagation and testing moon bounce echo.^[2]

FT8

Joe Taylor, K1JT, announced on June 29, 2017, the availability of a new mode in the WSJT-X software, FT8.^[11] FT8 stands for "Franke-Taylor design, 8-FSK modulation" and was created by Joe Taylor, K1JT and Steve Franke, K9AN. It is described as being designed for "multi-hop Es where signals may be weak and fading, openings may be short, and you want fast completion of reliable, confirmable QSO's".

According to Taylor, the important characteristics of FT8 are —

• T/R sequence length: 15 s
• Message length: 75 bits + 12-bit CRC
• FEC code: (174,87) LDPC
• Modulation: 8-FSK, keying rate = 6.25 baud; tone spacing = 6.25 Hz
• Waveform: Continuous phase, constant envelope
• Occupied bandwidth: 50 Hz
• Synchronization: three 7x7 Costas arrays (start, middle, end of transmission)
• Transmission duration: 79*1920/12000 = 12.64 s
• Decoding threshold: -24 dB (with a priori decoding)
• Operational behavior: similar to HF usage of JT9, JT65
• Multi-decoder: finds and decodes all FT8 signals in passband
• Auto-sequencing after manual start of QSO

Compared to the so-called "slow modes" (JT9, JT65, QRA64), FT8 is a few decibels less sensitive, but allows completion of QSOs four times faster. Bandwidth is greater than JT9, but about one-quarter of JT65A and less than one-half of QRA64. Compared with the "fast modes" (JT9E-H), FT8 is significantly more sensitive, has much narrower bandwidth, uses the vertical waterfall, and offers multi-decoding over the full displayed passband. The mode also supports two-pass decoding and use of "a priori (already known) information as it accumulates during a QSO".^[2]

There are alternative software packages available for JT65 including MultiPSK (a commercial package developed by F6CTE),^[14] and JT65-HF HB9HQX Edition (a free software package forked from the JT65-HF project developed by W6CQZ).^[15] The JT65-HF HB9HQX Edition software, along with the source code, may be obtained from SourceForge.^[16]

An article series on using the original JT65-HF software appeared in CQ Amateur Radio's October^[17] & November 2010^[18] issues. And MSHV ^[19] from LZ2HV recompiled from source code of WSJT-X with different GUI implementation both for Linux and Windows OS.

• Official WSJT website
• Official WSJT open source project information
• Italian FT8 Website

Winlink, or formally, Winlink Global Radio Email (registered US Service Mark), also known as the Winlink 2000 Network, is a worldwide radio messaging system that uses amateur-band radio frequencies and government frequencies to provide radio interconnection services that include email with attachments, position reporting, weather bulletins, emergency and relief communications, and message relay. The system is built and administered by volunteers and is financially supported by the Amateur Radio Safety Foundation.^[a]

Winlink networking started by providing interconnection services for amateur radio (also known as ham radio). It is well known for its central role in emergency and contingency communications worldwide. The system used to employ multiple central message servers around the world for redundancy, but in 2017–2018 upgraded to Amazon Web Services that provides a geographically-redundant cluster of virtual servers with dynamic load balancers and global content-distribution. Gateway stations have operated on sub-bands of HF since 2013 as the Winlink Hybrid Network, offering message forwarding and delivery through a mesh-like smart network whenever Internet connections are damaged or inoperable.^[2] During the late 2000s, it increasingly became what is now the standard network system for radio email, worldwide. Additionally, in response to the need for better disaster response communications in the mid to later part of the 2000s, the network was expanded to provide separate parallel radio email networking systems for the US Department of Homeland Security SHARES Winlink Radio Email System, along with other governments (non-amateur radio) services, also to include Non-government Organizations such as the US American Red Cross, the Austrian International Red Cross, and other such critical infrastructure Non-Government Organizations. Although these services are separate, and for reasons of security may be unknown to each other, the capability to cross services with complete Interoperability is available. For example, a US ham using Winlink on the amateur radio spectrum may email a Winlink user on the DHS SHARES Winlink system (non-amateur) radio service, which may then be picked up on the DHS SHARES Winlink network system. Of course, the originator of any service must be familiar with the regulatory environment of the recipient's service should it be another Winlink service.

E-mail via HF^[b] can be used nearly everywhere on the planet, and is made possible by connecting an HF single sideband (SSB) transceiver system to a computer, modem interface, and appropriate software. The HF modem technologies include PACTOR, Winmor (deprecated), ARDOP, Vara HF, and Automatic Link Establishment (ALE). VHF/UHF protocols include AX.25 Packet and Vara FM.

The Winlink system is open to properly licensed amateur radio operators, worldwide. The system primarily serves radio users without normal access to the internet, government and non-government public service organizations, medical and humanitarian non-profits, and emergency communications organizations. As of July 2008, there were approximately 12,000 radio users and approximately 100,000 Internet correspondents. Monthly traffic volume averages over 100,000 messages.^[3]

For offshore cruising yachts, Winlink is widely used as an alternative, or alongside, Sailmail, which is an HF PACTOR based-email system using marine HF frequencies rather than amateur, and unlike the amateur radio use of Winlink, allows business to be conducted over radio. In addition to email, Winlink uses a system called "Saildocs," and other file delivery methods, which allows properly licensed amateur radio cruisers to retrieve meteorological, maritime safety and other crucial files over Winlink email. As example, Winlink was found to be more useful in and around South Africa where best weather was provided by SAMNet (South African Mobile Maritime Net).^[4]

• 802.11 WiFi
• ALE (Automatic Link Establishment)
• APRS (Automatic Packet Reporting System)
• AX.25 Packet Radio
• D-Star
• PACTOR
• PACTOR-II
• PACTOR-III
• PACTOR-IV
• Winmor (deprecated)
• ARDOP
• Vara HF
• Vara FM
• TCP/IP (Telnet and other wireless technologies)

PACTOR-I, Winmor(deprecated), ARDOP, HSMM (WiFi), AX.25 packet, D-Star, TCP/IP, and ALE are non-proprietary protocols used in various RF applications to access the Winlink network systems. Later versions of PACTOR are proprietary and supported only by commercially available modems from Special Communications Systems GmbH. In amateur radio service, AirMail, Winlink Express, and other email client programs used by the Winlink system,^[5] disable the proprietary compression technology for PACTOR-II, PACTOR-III, and PACTOR-IV modems and instead relies on the open FBB protocol, also widely used worldwide by packet radio BBS forwarding systems.

In May 1995, the American Radio Relay League (ARRL) privately asked the FCC to change Part 97.309(a) to allow fully documented G-TOR, Clover, and original open source PacTOR (Pactor I) modes. The FCC granted this request in DA-95-2106 based on the ARRL's representation that it had worked with developers to ensure complete technical documentation of these codes were available to all amateur radio operators.^[6] However, subsequent versions of Pactor contained proprietary compression algorithms that prevent over-the-air interception.^[7] As of July 9, 2024, the Winlink Development Team has stated that their software only uses an open compressed binary format called Open B2F, which is publicly listed on the Winlink website, and replaces proprietary compression used by some manufacturers of protocols used.

In 2007, a US amateur radio operator filed a formal petition with the Federal Communications Commission (FCC)^[8] aimed at reducing the signal bandwidth in automatic operation subbands; but, in May 2008 FCC ruled against the petition.^[9] In the Official Order, FCC said, "Additionally, we believe that amending the amateur service rules to limit the ability of amateur stations to experiment with various communications technologies or otherwise impeding their ability to advance the radio art would be inconsistent with the definition and purpose of the amateur service.^[9] Moreover, we do not believe that changing the rules to prohibit a communications technology currently in use is in the public interest."^[9]

In 2013, the FCC ruled in Report and Order 13-1918 against the use of encryption in the US amateur radio bands for any purpose, including emergency communications. The FCC cited the need for all amateur radio communications to be open and unobscured, to uphold the Commission's long-standing requirement that the service be able to police itself.^[10]

Winlink itself uses point-to-point protocols that may be copied by a third party through methods provided by the authors of these protocols as well as from independent sources. Because the content of data is not obstructed on the amateur spectrum, those government agencies who do use Winlink for Continuity of Government and public safety emergency communications requested (or in some cases, mandated) that they be allowed to encrypt their messages.

On non-amateur radio frequencies worldwide, Winlink provides for encryption via AES-256 for its most used protocols, Pactor and VARA. Such transmission encryption, once set up properly, is seamless to the end-user and requires no additional effort, but is left up to the individual operator or government agency to setup.

In addition to "readers" being made available for protocols used by the Winlink system, in the US, all messages passing through licensed US amateur radio stations by radio are freely accessible by other licensed amateurs via the WinLink Open Message Viewer on the Winlink WebSite. Amateurs concerned about encryption are encouraged to help the US amateur radio community police itself by search and viewing such messages, and reporting messages if they spot a violation.^[11]

• Amateur radio emergency communications
• Automatic Link Establishment

• The official Winlink Web Site
• Winlink Research Project
• Winlink Tutorial
• Winlink wide-area HF MESH network
• Introduction to RMS Express Winlink client program
• Guida italiana completa per l'uso di RMS Express /-/ Winlink 2000
• The Wiki for Pat – a cross platform Winlink client
• Guia rápida en Español de introducción a la Red WL2K, Winmor y uso del RMS Express, (Spanish White Paper)