Introduction: FT4 is an experimental digital mode designed specifically for radio contesting. Like FT8, it uses fixed-length transmissions, structured messages with formats optimized for minimal QSOs, and strong forward error correction. But with 6 second sequences.
Further information regarding this new mode is attached.
General relaese of WSJT-X RC5 thats supports this mode will be on the 29th April 2019.