FT8 or Franke & Taylor 8 is a frequency shift keying digital mode that was released on June 29, 2017, by the creators Joe Taylor, K1JT, and Steve Franke, K9AN along with the software package WSJT. FT8 is a popular form of digital weak signal communication used primarily by amateur radio operators to communicate on amateur radio bands with a majority of traffic occurring on the HF amateur bands. It is currently the most popular digital mode on spotting networks such as PSK Reporter.
The mode offers operators the ability to communicate in unfavorable environments such as during low sunspot numbers, high RF noise, or during low power operations. With advances in signal processing technology, FT8 is able to decode signals with a signal-to-noise ratio as low as −20 dB, which is significantly lower than CW or SSB transmissions. The mode works by sending signals in 15-second blocks with 12.64 seconds of transmission time and 2.36 seconds of decode time, this gives the mode five words per minute effective transmission. The mode requires each computer to be synced up in time with each other with most users making use of either NTP or GPS to ensure transmissions fall in the proper window. This allows FT8 transmission to support up to 13 characters, the mode uses forward error correction to ensure proper transmission and decoding. As the mode is quite limited in the number of words that it can send, it only sends enough information to ensure contact with each station. There are multiple uses for FT8 including contesting, testing antennas, and scientific research.
Source: Wikipedia
Above image was captured from my PC running WSJT running in FT8 mode
