WSJT (software)

WSJT (software)
Name	WSJT
Developer	Joe Taylor, Steve Franke
Released	0 2001
Programming language	Fortran
Operating system	Microsoft Windows, Linux, macOS
Genre	Amateur radio software

WSJT (software). WSJT is a suite of computer programs designed for amateur radio communication under challenging conditions, such as weak signal propagation and high noise environments. Developed by Nobel laureate Joe Taylor and collaborator Steve Franke, it enables reliable contacts over long distances using digital modulation techniques. The software has become a cornerstone of the amateur radio satellite, moonbounce, and meteor scatter communities.

Overview

The primary function of WSJT is to facilitate digital modes of communication that are far more robust than traditional voice transmission or Morse code under poor signal-to-noise ratio conditions. It achieves this by employing sophisticated forward error correction and efficient protocols that allow for the exchange of minimal but essential data. The software suite is widely used for experimental communications on the VHF, UHF, and microwave bands, where signals are often at the threshold of detectability. Its development has been closely associated with the activities of the American Radio Relay League and various international amateur radio organizations.

Development and history

The initial development of WSJT began in 2001 by Joe Taylor, a professor at Princeton University and recipient of the Nobel Prize in Physics for his work on binary pulsars. Taylor's interest in radio astronomy and weak-signal detection directly informed the software's design philosophy. Key collaborator Steve Franke contributed significantly to the codebase and protocol development. Early versions were written in Fortran and focused on modes for meteor scatter and EME. The software's evolution has been documented in numerous articles in QST and the Journal of the Society of Amateur Radio Astronomers.

Modes and protocols

The WSJT suite implements several distinct digital protocols, each optimized for a specific type of propagation or communication goal. Core modes include JT65, designed for extremely weak, steady signals like those in EME; JT9, a more efficient successor to JT65; and FT8, a very fast mode that has revolutionized HF digital amateur radio due to its speed and reliability. Other significant modes are MSK144 for meteor scatter, QRA64 for tropospheric and sporadic E openings, and WSPR, which is used for beaconing and radio propagation research.

Technical operation

Technically, WSJT modes use precise synchronization to UTC and transmit data in short, structured transmissions. They employ low-density parity-check codes for powerful forward error correction, allowing decoders to recover messages from signals well below the noise floor. The software typically requires a stable personal computer sound card interface to the radio transceiver, with timing often disciplined by NTP or a GPS disciplined oscillator. Signal processing tasks like FFT decoding are performed in real-time, presenting results to the operator in a decoded text display.

Applications in amateur radio

WSJT has enabled dramatic expansions in amateur radio activities, particularly in the VHF and above communities. It is the standard tool for moonbounce operations, allowing stations with modest antennas to make IARU-recognized contacts reflecting signals off the Moon. The software is also indispensable for making contacts via random meteor trails in the atmosphere and for working through low-Earth orbit satellites. On the HF bands, modes like FT8 have led to an explosion in digital DXing, facilitating global contacts with minimal power and compromised antennas.

Software implementation

The original WSJT software is implemented in Fortran, with source code available to the public. A separate, popular graphical user interface implementation for Microsoft Windows is provided by MAP65 for EME use. The widespread adoption of the protocols has led to third-party implementations, most notably WSJT-X, a complete rewrite in C++ that is now the mainstream version maintained by Taylor and Franke. WSJT-X offers a more modern interface, supports all current modes, and runs on Microsoft Windows, Linux, and macOS operating systems. Development discussions often occur within the AMSAT community and on internet forums like the QRZ.com forums.

Category:Amateur radio software Category:Digital audio Category:Free software