<div dir="ltr"><div><br></div><p style="margin-bottom:20px;margin-top:0px;color:rgb(142,142,142);font-family:"Open Sans",sans-serif;line-height:22.4px"><span style="color:rgb(0,0,0)">Steve (K9AN) and I have developed a potential new mode for WSJT-X. We’re </span><br><span style="color:rgb(0,0,0)">calling the mode “FT8” (Franke-Taylor design, 8-FSK modulation).</span></p><p style="margin-bottom:20px;margin-top:0px;color:rgb(142,142,142);font-family:"Open Sans",sans-serif;line-height:22.4px"><span style="color:rgb(0,0,0)">FT8 is designed for situations like multi-hop Es where signals may be </span><br><span style="color:rgb(0,0,0)">weak and fading, openings may be short, and you want fast completion of </span><br><span style="color:rgb(0,0,0)">reliable, confirmable QSOs.</span></p><p style="margin-bottom:20px;margin-top:0px;color:rgb(142,142,142);font-family:"Open Sans",sans-serif;line-height:22.4px"><span style="color:rgb(0,0,0)">Important characteristics of FT8:</span></p><p style="margin-bottom:20px;margin-top:0px;color:rgb(142,142,142);font-family:"Open Sans",sans-serif;line-height:22.4px"><span style="color:rgb(0,0,0)">– T/R sequence length: 15 s</span><br><span style="color:rgb(0,0,0)">– Message length: 75 bits + 12-bit CRC</span><br><span style="color:rgb(0,0,0)">– FEC code: LDPC(174,87)</span><br><span style="color:rgb(0,0,0)">– Modulation: 8-FSK, keying rate = tone spacing = 5.86 Hz</span><br><span style="color:rgb(0,0,0)">– Waveform: Continuous phase, constant envelope</span><br><span style="color:rgb(0,0,0)">– Occupied bandwidth: 47 Hz</span><br><span style="color:rgb(0,0,0)">– Synchronization: three 7×7 Costas arrays (start, middle, end of Tx)</span><br><span style="color:rgb(0,0,0)">– Transmission duration: 79*2048/12000 = 13.48 s</span><br><span style="color:rgb(0,0,0)">– Decoding threshold: -20 dB (perhaps -24 dB with AP decoding, TBD)</span><br><span style="color:rgb(0,0,0)">– Operational behavior: similar to HF usage of JT9, JT65</span><br><span style="color:rgb(0,0,0)">– Multi-decoder: finds and decodes all FT8 signals in passband</span><br><span style="color:rgb(0,0,0)">– Auto-sequencing after manual start of QSO</span></p><p style="margin-bottom:20px;margin-top:0px;color:rgb(142,142,142);font-family:"Open Sans",sans-serif;line-height:22.4px"><span style="color:rgb(0,0,0)">*Comparison with slow modes JT9, JT65, QRA64:* FT8 is a few dB less </span><br><span style="color:rgb(0,0,0)">sensitive but allows completion of QSOs four times faster. Bandwidth is </span><br><span style="color:rgb(0,0,0)">greater than JT9, but about 1/4 of JT65A and less than 1/2 QRA64.</span></p><p style="margin-bottom:20px;margin-top:0px;color:rgb(142,142,142);font-family:"Open Sans",sans-serif;line-height:22.4px"><span style="color:rgb(0,0,0)">*Comparison with fast modes JT9E-H:* FT8 is significantly more </span><br><span style="color:rgb(0,0,0)">sensitive, has much smaller bandwidth, uses the vertical waterfall, and </span><br><span style="color:rgb(0,0,0)">offers multi-decoding over the full displayed passband.</span></p><p style="margin-bottom:20px;margin-top:0px;color:rgb(142,142,142);font-family:"Open Sans",sans-serif;line-height:22.4px"><span style="color:rgb(0,0,0)">*Still to come, not yet implemented:* We plan to implement signal </span><br><span style="color:rgb(0,0,0)">subtraction, two-pass decoding, and use of “a priori” (already known) </span><br><span style="color:rgb(0,0,0)">information as it accumulates during a QSO.</span></p><p style="margin-bottom:20px;margin-top:0px;color:rgb(142,142,142);font-family:"Open Sans",sans-serif;line-height:22.4px"><span style="color:rgb(0,0,0)">Three extra bits are available in the message payload, with uses yet to </span><br><span style="color:rgb(0,0,0)">be defined. We have in mind special message formats that might be used </span><br><span style="color:rgb(0,0,0)">in contests, and the like. Your considered suggestions for use of these </span><br><span style="color:rgb(0,0,0)">bits are very welcome!</span></p><p style="margin-bottom:20px;margin-top:0px;color:rgb(142,142,142);font-family:"Open Sans",sans-serif;line-height:22.4px"><span style="color:rgb(0,0,0)">K1JT, K9AN, and G4WJS have conducted on-the-air tests of FT8 with </span><br><span style="color:rgb(0,0,0)">excellent results. We’re now at a stage where tests under a wider range </span><br><span style="color:rgb(0,0,0)">of conditions are desirable. If you can build WSJT-X from source code </span><br><span style="color:rgb(0,0,0)">revision r7750 or later, and would like to help, please do so and report </span><br><span style="color:rgb(0,0,0)">your results to us! Pre-built installation packages will be made </span><br><span style="color:rgb(0,0,0)">available after further testing is completed.</span></p><div><br></div>-- <br><div class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><table width="34%" cellspacing="0" cellpadding="0" border="0">
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<p><font size="2">73's</font></p><div style="text-align:center"><font size="1">***********************************</font><br><font size="1">CT1JIB / <b>Jorge Santos</b></font><br><br><font size="1">***********************************</font></div></td></tr></tbody></table></div></div></div></div></div></div></div></div></div></div></div></div></div></div>
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