The Logbook of The World (LoTW) Committee worked with WSJT-X developer Joe Taylor, K1JT, to coordinate the creation of FST4 among WSJT-X, the ADIF standard, and LoTW.

Currently, the FST4 is only supported in a newly released beta version of the WSJT-X.


The new beta released includes digital protocols particularly designed for communication on LF and MF bands, like the 2200 meters and 630 meters, and its developers say that during its first few months of testing, contacts have crossed intercontinental paths numerous times on those bands.

Both modes offer a range of options for T/R-sequence lengths and threshold decoding sensitivities extending well into the –40 dB range, developers said.

Captioned in the photo: Joe Turner

Committee’s Action to Avoid

The committee’s action was to avoid the sort of confusion that cropped up among LoTW users logging contacts in FT4 when that protocol was first included in WSJT-X. In the case of FST4, the committee acted proactively to help users avoid difficulties and obtain the maximum number of contact matches.

ADIF Standard

The ADIF standard has been updated to support FST4 as a sub-mode of MFSK, and configuration file CONFIG.xml for LoTW has been updated to version 11.13, accordingly, to support FST4. Users will be offered the update when they run TQSL.

The FST4 Is Only Available

Again, FST4 is only available in WSJT-X. An ADIF file emitted by WSJT-X should properly identify FST4, so that contacts will upload smoothly into LoTW, provided the CONFIG file has been updated.