New Digital Mode from K1JT

Just got this from Bob G3WKW:
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 7x7 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.

Three extra bits are available in the message payload, with uses yet tobe defined.  We  have in mind special message formats that might be used in contests, and the like.  Your considered suggestions for use of these bits are very welcome!

K1JT, K9AN, and G4WJS have conducted on-the-air tests of FT8 with excellent results.  We're now at a stage where tests under a wider range of conditions are desirable.  If you can build WSJT-X from source code revision r7750 or later, and would like to help, please do so and report your results to us!  Pre-built installation packages will be made available after further testing is completed.

Suggestions for FT8 setup and examples of use can be found in a screen shot posted here: http://physics.princeton.edu/pulsar/k1jt/ft8.png

We look forward to receiving your feedback.

   -- 73, Joe, K1JT

It will help to have some initial frequency coordination among those
testing the new FT8 mode in WSJT-X v1.7.1.

To help get things started, we suggest using the following frequencies:

Band    MHz
-------------
 160   1.841
  80   3.579
  40   7.079
  30  10.141
  20  14.079
  17  18.105
  15  21.079
  12  24.920
  10  28.079
   6  50.313
   4  70.094
-------------

Most of these suggestions follow a simple guideline: add 3 kHz to the
commonly used JT65 dial frequency.

For 6 meters we suggest using 50.313, which should be consistent with
band plans in all IARU Regions.  (Six meter activity that's now on
50.276, world-wide, might be moved to 50.310.)

We are very much open to suggestions for changes in the above table.

   -- 73, Joe, K1JT