1. Introduction

WSJT-X is an open source computer program designed to facilitate basic amateur radio communication using very weak signals. The first four letters in the program name stand for “Weak Signal communication by K1JT,” while the suffix “-X” indicates that WSJT-X started as an extended branch of an earlier program, WSJT, which was first released by Joe Taylor, K1JT, in 2001. Bill Somerville, G4WJS, Steve Franke, K9AN, and Nico Palermo, IV3NWV, have been major contributors to development of WSJT-X since 2013, 2015, and 2016, respectively. Bill Somerville died unexpectedly in December 2021; Uwe Risse, DG2YCB, joined the core development team soon afterward, followed by Brian Moran, N9ADG in 2022, John Nelson, G4KLA and Charlie Suckling, DL3WDG in 2024, and Roger Rehr, W3SZ, in 2025. Over the years many other hams have contributed to WSJT-X development in more limited ways. We are extremely grateful for all of these contributions.

WSJT-X provides flexible rig control for nearly all modern radios used by amateurs and a wide variety of special aids such as automatic Doppler tracking for Earth-Moon-Earth (EME) QSOs and lunar-Echo testing. The program analyzes received passbands up to 5 kHz wide and runs equally well on Windows, Macintosh, and Linux systems.

WSJT-X Improved was developed by Uwe Risse, DG2YCB, starting in 2020, and since 2021 it has evolved cooperatively with WSJT-X. The Improved versions build on the WSJT-X code base and offer three different arrangements of main-window controls as well as new features for enhanced operational functionality. Compatibility between WSJT-X Improved and standard WSJT-X has been carefully maintained, so that user transitions between the two programs are straightforward. Optional settings, station logs, and the like are consistently preserved and used by both program versions. Innovations from WSJT-X Improved have been ported back into WSJT-X at various times; with program release 3.0, most features of WSJT-X and WSJT-X Improved have been merged. Indeed, WSJT-X 3.0 and the WSJT-X Improved 3.0 version with original user interface were almost identical. Starting with program release 3.1, WSJT-X Improved and WSJT-X are different again. However, we use the Improved label in this User Guide only when necessary to make clear distinctions between the two programs.

Development of both WSJT-X and WSJT-X Improved will continue. The Improved version provides a familiar platform for trying out and optimizing possible new features. Updates and new releases of WSJT-X Improved will be more frequent than those for standard WSJT-X. If you are interested in trying and using the very latest features you should watch for releases of WSJT-X Improved. Successful innovations will be incorporated in WSJT-X.

Version Numbers for our programs have major, minor, and patch numbers separated by periods: for example, WSJT-X 2.7.0 or WSJT-X Improved 2.7.0. Temporary release candidates are sometimes made in advance of a new general-availability (GA) release, in order to obtain user feedback. Release candidates are given version labels such as 2.7.0-rc1, 2.7.0-rc2, etc., leading up to the general availability (GA) release of version 2.7.0. Release candidates should be used only during a defined testing period, and they carry an implicit obligation to provide feedback to the program developers. Release candidates should not be used on the air after a GA release with the same number.

MAP65 and QMAP are companion programs written by K1JT to facilitate Earth-Moon-Earth (EME, or "Moonbounce") communication with digital protocols developed for WSJT and WSJT-X. When used with radio-frequency hardware providing coherent signal channels for two orthogonal polarizations, MAP65 can yield automatic polarization-matched reception for every JT65 or Q65 signal in a 90 kHz sub-band. QMAP uses a single polarization channel and only the Q65 mode, also covering a 90 kHz sub-band. It works cooperatively with WSJT-X to provide automatic Doppler compensation and other features important for EME, especially on 1296 MHz and higher amateur bands. These programs are installed automatically along with WSJT-X (but MAP65 only on the Windows platform).

Hamlib is an independent, open-source software library that provides a consistent Application Programming Interface (API) for computer control of radios used by hams. Hamlib is essential to all features of WSJT-X that control your radio, and the latest stable version is included with all of our program releases. Like WSJT-X, Hamlib is under constant development by a group of volunteers. When necessary — perhaps when you acquire a very new radio — you can update your active Hamlib version from within WSJT-X.

1.1. New in Version 3.1

A new 3.1 release of WSJT-X Improved is currently under development. Some features may not yet be included in this User Guide.

We recommend that you always make backup copies of your WSJT-X.ini and wsjtx_log.adi files before installing program releases that involve major changes!

New features compared to WSJT-X Improved 3.0.0 251212:

1. Introduction of a new FT2 mode

  • FT2 is a super-fast 77-bit mode with TR periods of 3.75 seconds (= 1/2 of FT4).

  • It goes back to experiments by Joe and Steve in 2019, which later became FT4. IU8LMC recently introduced "his" FT2 mode with slightly modified parameters, but refused to publish the source code. This contradicts ham spirit, and violates GPLv3 licence. I thought the best answer was to reverse engineer "his" FT2 mode and make it open source.

  • Note that FT2 is still experimental. I haven’t decided yet whether we’ll keep it. Let’s see if FT2 proves itself alongside FT4, or if it’s just a short-lived hype.

2. Support of QSOs between two stations with non-standard or compound callsigns for the 77-bit modes (FT8, FT4, FT2, MSK144, Q65, FST4)

The following QSO types are now possible:

  • two non-standard callsigns (e.g. DG123YCB with W250USA)

  • two compound callsigns (e.g. DG2YCB/QRP with W1XYZ/YOTA, or HB9/DG2YCB with KP5/W1XY)

  • non-standard callsign and compound callsign (e.g. DG123YCB with W1XYZ/QRP)

  • non-standard callsign and /P callsign (e.g. DG123YCB with W1XYZ/P)

  • two standard callsigns with /P, /M, /R or whatever (e.g. DG2YCB/MM with W1XYZ/P)

Important:

  • Both stations must use WSJT-X Improved 3.1 (or compatible software) for such QSOs. I noticed that some beta builds of JTDX and MSHV seem to be compatible with these message formats, however, the standard WSJT-X would get stuck in an endless autoseq loop.

  • All previous message types are still fully supported, making WSJT-X Improved 3.1 fully backward compatible.

  • These new QSO types cannot be used in special operating activities (contest modes), as the available 77 bits are not sufficient for this purpose.

3. New technology for the MAP65 program

  • The map65.exe file is now less than 1/4 the size it was before. This new technology will (hopefully) also bring stability improvements.

4. Various minor improvements and fixes

  • Added a new option to skip a8 decodes for the multithreaded FT8 decoder (MTD).

  • The band hopping interval can now be switched between 1 minute and 2 minutes. See the new checkbox on the Settings | General tab.

  • The "Less button coloring" option has been removed because it was rarely used.

  • Fixed a flaw that caused FT4 decodes not to be displayed when the program was started with CQonly enabled.

  • Bugfix: Country names are no longer accidentally displayed when in FST4W mode.

  • Fixed an inconsistency regarding the highlighting of prefixes.

  • Transmissions above 5362 kHz on 60m are allowed for UK stations again. Only Tx frequencies between 5358 and 5362 kHz are prevented now.

  • Better visibility of the Settings | Tx Macros tab when dark style is enabled.

  • Added an option to log the dial frequency instead of the actual Tx frequency.

5. Support of the new Hamlib 5 series

  • The Update Hamlib function now supports both Hamlib 4 and Hamlib 5. The required version of the libhamlib DLL file is detected automatically.

Always use the latest builds available before reporting any bugs!

1.2. Documentation Conventions

This guide includes many screen shots to illustrate user settings and program features. Keep in mind that WSJT-X is a multi-platform application; the detailed appearance of windows and user controls will be different in Windows, Linux, or macOS environments. The underlying functionality is the same on all operating systems, however. Where desirable we call special attention to important platform differences.

Most people access the WSJT-X User Guide primarily through a browser. Use the browser’s search function, generally invoked from the keyboard with the keys CTRL+F, to search the guide for help on a particular topic or keyword.

The names of WSJT-X windows, menus, and on-screen controls are displayed in this manual in boldface type, as in Wide Graph. File names and information entered via keyboard is shown in a monospace font, for example all.txt.

In this manual the following icons call attention to particular types of information:

Tips on program features or capabilities that might otherwise be overlooked.
Notes containing information that may be of interest to particular classes of users.
Warnings about usage that could lead to undesired consequences.

1.3. User Interface in Other Languages

The WSJT-X user interface (UI) is now available in many languages. When a translated UI is available for the computer’s default System Language, it will appear automatically on program startup. The UI language may be overridden if desired by starting WSJT-X with a command line option. For example, to start WSJT-X with its user interface in Spanish or Japanese, start a command-prompt window and enter one of these the commands:

wsjtx --language es

wsjtx --language ja

The top portion of the main window will then look like one of the following examples:

Main Window es
Main Window ja

1.4. How You Can Contribute

WSJT-X is part of an open-source project released under the GNU General Public License (GPLv3). If you have programming or documentation skills or would like to contribute to the project in other ways, please make your interests known to the development team. We especially encourage those with translation skills to volunteer their help, either for this User Guide or for the program’s user interface.

The project’s source-code repository can be found at SourceForge. Bug reports and suggestions for new features, improvements to the WSJT-X User Guide, etc., may be sent to one of the email lists listed in the Support section. You must join the group in order to post messages to the email list.

1.5. License

Before using WSJT-X, please read our licensing terms here.

2. Modes

WSJT-X offers eleven different protocols or modes: FST4, FT4, FT8, JT4, JT9, JT65, Q65, MSK144, WSPR, FST4W, and Echo. The first eight are designed for making reliable QSOs under weak-signal conditions. They use nearly identical message structure and source encoding. JT65 was designed for EME (“moonbounce”) on VHF and higher bands and is mostly used for that purpose today. Q65 is particularly effective for tropospheric scatter, rain scatter, ionospheric scatter, TEP, and EME on VHF and higher bands, as well as other types of fast-fading signals. JT9 was designed for the HF and lower bands. Its submode JT9A is 1 dB more sensitive than JT65 while using less than 10% of the bandwidth. JT4 offers a wide variety of tone spacings and has proven highly effective for EME on microwave bands up to 24 GHz. The “slow” modes use timed sequences of alternating transmission and reception. JT4, JT9, and JT65 use one-minute sequences, so a minimal QSO takes four to six minutes — two or three transmissions by each station, one sending in odd UTC minutes and the other even. FT8 is four times faster (15-second T/R sequences) and less sensitive by a few dB. FT4 is faster still (7.5 s T/R sequences) and especially well-suited for radio contesting. FST4 is designed especially for the LF and MF bands. Both FST4 and Q65 offer a wide variety of timed sequence lengths, and Q65 a range of tone spacings for different propagation conditions. On the HF bands, world-wide QSOs are possible with any of these modes using power levels of a few watts (or even milliwatts) and compromise antennas. On VHF bands and higher, QSOs are possible (by EME, scatter, and other propagation types) at signal levels 10 to 15 dB below those required for CW.

MSK144, and optionally submodes JT9E-H are “fast” protocols designed to take advantage of brief signal enhancements from ionized meteor trails, aircraft scatter, and other types of scatter propagation. These modes use timed sequences of 5, 10, 15, or 30 s duration. User messages are transmitted repeatedly at high rate (up to 250 characters per second for MSK144) to make good use of the shortest meteor-trail reflections or “pings”. MSK144 uses the same structured messages as the slow modes and optionally an abbreviated format with hashed callsigns.

Note that some of the modes classified as slow can have T/R sequence lengths as short the fast modes. “Slow” in this sense implies message frames being sent only once per transmission. The fast modes in WSJT-X send their message frames repeatedly, as many times as will fit into the Tx sequence length.

WSPR (pronounced “whisper”) stands for Weak Signal Propagation Reporter. The WSPR protocol was designed for probing potential propagation paths using low-power transmissions. WSPR messages normally carry the transmitting station’s callsign, grid locator, and transmitter power in dBm, and with two-minute sequences they can be decoded at signal-to-noise ratios as low as -31 dB in a 2500 Hz bandwidth. FST4W is designed for similar purposes, but especially for use on LF and MF bands. It includes optional sequence lengths as long as 30 minutes and reaches sensitivity thresholds as low as -45 dB. Users with internet access can automatically upload WSPR and FST4W reception reports to a central database called WSPRnet that provides a mapping facility, archival storage, and many other features.

Echo mode allows you to detect and measure your own station’s echoes from the moon and to make other measurements useful for optimizing your EME station’s performance.

3. System Requirements

  • SSB transceiver and antenna

  • Computer running Windows 7 or later, macOS 10.13 or later, or Linux

  • 1.5 GHz or faster CPU and 200 MB of available memory; faster machines are better

  • Monitor with at least 1024 x 780 resolution

  • Computer-to-radio interface using a serial port or equivalent USB device for T/R switching, or CAT control, or VOX, as required for your radio-to-computer connections

  • Audio input and output devices supported by the operating system and configured for sample rate 48000 Hz, 16 bits

  • Audio or equivalent USB connections between transceiver and computer

  • A means for synchronizing the computer clock to UTC within ±1 second

4. Installation

WSJT-X Improved is available with three different Graphical User Interfaces (GUIs). Various installation packages are available for Windows, Linux, MacOS, and for the Raspberry Pi. They can be downloaded from the WSJT-X Improved project page: https://sourceforge.net/projects/wsjt-x-improved/. Go to the “Files” tab to see the available versions.

For technical reasons, each of the three GUI version uses a different installer. The default download has the standard WSJT-X GUI. It looks like this: