Digital

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 esoteric 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]

History

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.

Communication modes provided

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]

FSK441

FSK441, introduced in 2001 as the first communications mode included with WSJT,^[3] is designed to support meteor scatter communication using radio-reflecting meteor trails.^[2] The bursts of signal created by such trails are commonly referred to as "pings", due to their characteristic sound. Such pings may be as short as a tenth of a second and carry enough information to complete at least one stage of a contact.^[6] FSK441 employs multi-frequency shift keying using four tones, at a data rate of 441 baud. Because of the choice of character codes in the protocol, it is self-synchronizing and does not require an explicit synchronization tone.^[6] FSK441 is generally used on the 2-meter and 70-centimeter amateur bands. Contacts may be made at almost any time (that is, a meteor shower is not required to be in progress) at distances of up to 1400 miles (2250 km).^[6]

Transmitted messages include at least one space, the FSK441 decoding algorithm uses that space character as a syncword for zero-overhead synchronization.^[6]

This mode is no longer included in WSJT-X as of version 2.1.2.

JT6M

JT6M, introduced in late 2002,^[7] is intended for meteor scatter and other ionospheric scattering of signals, and is especially optimized for the 6-meter band. The mode also employs multiple frequency-shift keying, but at 44 tones. One of the tones is a synchronization tone, leaving 43 tones to carry data (one tone per character in the character set, which includes alphanumerics and some punctuation). The symbol rate is 21.53 baud; the actual data rate as encoded for transmit is 14.4 characters per second. The mode is known for sounding "a bit like piccolo music".^[7]

This mode is no longer included in WSJT-X as of version 2.1.2.

JT65

JT65, developed and released in late 2003,^[3] is intended for extremely weak but slowly varying signals, such as those found on troposcatter or Earth-Moon-Earth (EME, or "moonbounce") paths.^[2] It can decode signals many decibels below the noise floor in a 2500 Hz band (note that SNR in a 2500 Hz band is approximately 28 dB lower than SNR in a 4 Hz band, which is closer to the channel bandwidth of an individual JT65 tone), and can often allow amateurs to successfully exchange contact information without signals being audible to the human ear. Like the other modes, multiple-frequency shift keying is employed; unlike the other modes, messages are transmitted as atomic units after being compressed and then encoded with a process known as forward error correction (or "FEC"). The FEC adds redundancy to the data, such that all of a message may be successfully recovered even if some bits are not received by the receiver. (The particular code used for JT65 is Reed-Solomon.) Because of this FEC process, messages are either decoded correctly or not decoded at all, with very high probability. After messages are encoded, they are transmitted using MFSK with 65 tones.^[8]

Operators have also begun using the JT65 mode for contacts on the HF bands, often using QRP (very low transmit power);^[9] while the mode was not originally intended for such use, its popularity has resulted in several new features being added to WSJT in order to facilitate HF operation.

JT9

JT9, intended for MF and HF use, was introduced in WSJT-X, which was at the time an experimental version of WSJT.^[10] It uses the same logical encoding as JT65, but modulates to a 9-FSK signal. With 1-minute transmission intervals, JT9 occupies less than 16 Hz bandwidth. (JT9 also had versions designed for longer transmission intervals of 2 minutes, 5 minutes, 10 minutes or 30 minutes. Those extended versions took increasingly less bandwidth and permitted reception of even weaker signals.)

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]

FT4

In 2019, Taylor, et al., introduced FT4, an experimental protocol which is similar to FT8 but has a shorter T/R sequence length for faster contest exchanges. FT4 accomplishes this increase in speed by using Gaussian frequency-shift keying and using 90 Hz of bandwidth.^[12][13]

Alternative software for JT65

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.

References

External links

• 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]

Network

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^[b] 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 1990s and late 2000s, it increasingly became what is now the standard network system for amateur 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 MARS, UK Cadet, Austrian Red Cross, the US Department of Homeland Security SHARES HF Program, and other groups.

Amateur radio HF e-mail

Generally, e-mail communications over amateur radio in the 21st century is now considered normal and commonplace.^{[citation needed]} E-mail via high frequency^[b] (HF) 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.

Amateur radio HF e-mail guidelines

Amateur radio users in each country follow the appropriate regulatory guidelines for their license. Some countries may limit or regulate types of amateur messaging (such as e-mail) by content, origination location, end destination, or license class of the operator. Origination of third party messages (messages sent on behalf of, or sent to, an end destination who is not an amateur operator) may also be regulated in some countries; those that limit such third party messages normally have exceptions for emergency communications. In accordance with long standing amateur radio tradition, international guidelines and FCC rules section 97.113, hams using the Winlink system are advised that it is not appropriate to use it for business communications.

Users

The Winlink system is open to properly licensed amateur radio operators. 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. Duly authorized MARS operators may utilize the MARS part of the system. 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 yachtspeople 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. As well as email the service uses a system called Saildocs, which allows cruisers to retrieve meteorological, maritime safety and other crucial files over email. 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][5][6]

Supported radio technologies

• 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)

Technical protocols

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,^[7] 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.

Controversies and US regulatory issues

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.^[8] However, subsequent versions of Pactor contained proprietary compression algorithms that prevent over-the-air interception.^[9]

In 2007, a US amateur radio operator filed a formal petition with the Federal Communications Commission (FCC)^[10] aimed at reducing the signal bandwidth in automatic operation subbands; but, in May 2008 FCC ruled against the petition.^[11] 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.^[11] Moreover, we do not believe that changing the rules to prohibit a communications technology currently in use is in the public interest."^[11]

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.^[12]

In spite of FCC rulings DA 95-2106 and DA 13-1918, Winlink advocates continue to use the proprietary versions of Pactor and other undocumented data formats that cannot be eavesdropped, and continue to press the FCC for encrypted data transmissions in amateur radio, as exemplified in a Winlink petition to the FCC for legalized encryption of the US amateur spectrum while seeking broader spectrum allocations in response to the Puerto Rico hurricanes of 2017.^[13]

Opponents warn that the continual lack of enforcement by the FCC and continued allowance of "effectively encrypted" e-mail traffic in the amateur bands is a national security threat, and ham operators have written to the US Congress about the threat.^{[14][15][16][17][18]}

However, 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. https://winlink.org/content/us_amateur_radio_message_viewer

The Board of Directors of the Amateur Radio Safety Foundation, Inc. has written FCC Chairman Ajit Pai, other Federal Communications Commission members, and FCC administrators to correct inaccuracies in opponents' claims.^[19]

See also

• Amateur radio emergency communications
• Automatic Link Establishment
• PACTOR
• Winmor

Footnotes

References

External links

• 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)