Nobel Laureate Joe Taylor, K1JT, the developer of the popular WSJT “weak-signal communication” software suite is advising users to avoid what he called “unauthorized” versions of his software. He said problems could result by using these builds on the air, and any results that might be shared with the broader user community would be unhelpful. “Third-party individuals — ie, others not part of the WSJT development team — have been compiling WSJT-X from the open-source code and making unauthorized ‘releases’ of their builds,” Taylor said September 8 in a discussionof WSJT-X “fast modes” on his website. “I do not recommend use of these builds on the air. If you operate with one of these unauthorized ‘rXXXX’ code revisions in our experimental code branch, you have no idea what you’ve got.” Taylor said that such programs “quite possibly” have been built from an intermediate, temporary “save” of various files that were not intended to produce a usable program. Subsequent observations regarding what does or does not work, he said, then become “worse than useless. [T]hey waste your time and ours.” WSJT-X implements JT9, which Taylor has described as “a new mode optimized for weak-signal communication on the LF, MF, and HF bands.” Taylor said JT9 is about 2 dB more sensitive than JT65 while using less than 10 percent of the bandwidth. WSJT-X is an “experimental” or “extended” package. Plans call for the eventual inclusion of other popular modes now supported in WSJT. A new alpha release of experimental WSJT-X v1.6.1, r5865, includes major improvements to the JTMSK decoder. Taylor also recently posted information about new “Fast JT9” submodes for meteor-scatter communication on 28 and 50 MHz. The post includes a brief development history and instructions. “Since its origin in the dark ages (ca 2001) WSJT has supported ‘fast’ modes (designed for meteor scatter, etc) and ‘slow’ modes (optimized for EME and other weak-signal propagation types),” he said. “The most recent new mode, JT9, now has both fast and slow submodes.” He said the new, experimental JT9 submodes use the same message structure, encoding, and modulation type as JT9A (the original version), but wider tone spacing and optional faster keying rates. Among other improvements, it features a 5× speed increase for the fast JT9 decoder. More information on the WSJT software suite is available on Taylor’s website.