The team is ready for this new mode. We’ll be active also on FT8, more infos coming soon !
Read with us the explanations about the new mode by the “guru” and Nobel Prize, John Taylor:
“Steve (K9AN) and I have developed a potential new mode for WSJT-X. We’re calling the mode “FT8” (Franke-Taylor design, 8-FSK modulation).
FT8 is designed for situations like multi-hop Es where signals may be weak and fading, openings may be short, and you want fast completion of
reliable, confirmable QSOs.
Important characteristics of FT8:
– T/R sequence length: 15 s
– Message length: 75 bits + 12-bit CRC
– FEC code: LDPC(174,87)
– Modulation: 8-FSK, keying rate = tone spacing = 5.86 Hz
– Waveform: Continuous phase, constant envelope
– Occupied bandwidth: 47 Hz
– Synchronization: three 7×7 Costas arrays (start, middle, end of Tx)
– Transmission duration: 79*2048/12000 = 13.48 s
– Decoding threshold: -20 dB (perhaps -24 dB with AP decoding, TBD)
– Operational behavior: similar to HF usage of JT9, JT65
– Multi-decoder: finds and decodes all FT8 signals in passband
– Auto-sequencing after manual start of QSO
*Comparison with slow modes JT9, JT65, QRA64:* FT8 is a few dB less sensitive but allows completion of QSOs four times faster. Bandwidth is
greater than JT9, but about 1/4 of JT65A and less than 1/2 QRA64.
*Comparison with fast modes JT9E-H:* FT8 is significantly more sensitive, has much smaller bandwidth, uses the vertical waterfall, and
offers multi-decoding over the full displayed passband.
*Still to come, not yet implemented:* We plan to implement signal subtraction, two-pass decoding, and use of “a priori” (already known)
information as it accumulates during a QSO. 73, Joe, K1JT”