I made my first QSO with the new mode with N8JX. It seems to work smoothly. One thing noticed it does not seem that bandpass decoding is available yet? I could not decode until I placed the marker on top of his signal.
73 Jay KA9CFD -----Original Message----- From: Joe Taylor [mailto:j...@princeton.edu] Sent: June 29, 2017 15:33 To: WSJT software development <wsjt-devel@lists.sourceforge.net> Subject: [wsjt-devel] FT8: Potential new mode for fast QSOs Dear Development Colleagues, 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 to be 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 ---------------------------------------------------------------------------- -- Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
