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FT8 Digital Mode

Joe Taylor, K1JT, announced on June 29, 2017 the availability of a new mode in the WSJT-X software, FT8.stands for "Franke-Taylor design, 8-FSK modulation" and was created by Joe Taylor, K1JT and Steve Franke, K9AN. It is described as being designed for "multi-hop Es where signals may be weak and fading, openings may be short, and you want fast completion of reliable, confirmable QSO's".

According to J. Taylor, the important characteristics of FT8 are:

  • 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 7x7 Costas arrays (start, middle, end of Tx)
  • Transmission duration: 79*2048/12000 = 13.48 s
  • Decoding threshold: -20 dB (perhaps -24 dB with a priori 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

Compared to the so called 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. Compared with the 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. Features not yet implemented include signal subtraction, two-pass decoding, and use of a priori (already known) information as it accumulates during a QSO.

 

FT-8, the new HF/6m digital mode, introduction for beginners

Here is a new digital mode that comes to you from the makers of JT-9 and JT-65.. Called FT-8 (Franke-Taylor design, 8FSK modulation) 

A weak signal mode that is not as sensitive to JT-65/9 but definitely something that will work when voice and CW will not. This is an introduction to someone who has never heard of it, or never has used JT-65 before. It may not be for everyone, but everyone should try it.

Watch FT-8, The New HF/6m Digital Mode, Introduction For Beginners 

 

WSJT software 
https://physics.princeton.edu/pulsar/k1jt/wsjtx.html

 

 

 Westlakes Club News  VK2ATZ broadcast Sunday's 9.00hrs on the VK2RTZ Repeater on 146.775MHz
Westlakes Amateur Radio Club Inc. York Street, Teralba NSW