New Digital mode commimg soon. FT8

New Digital mode commimg soon. FT8

Postby N5JEH » Thu Jun 29, 2017 1:44 pm

K1JT and crew are about to release a new mode within WSJT-X
It is FTB Only problem is that all of these modes will soon be moving above 50.300 to keep up with the rest of the world.

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.


FT8 is good for intercontinental DX on 6
meters, and there is strong pressure from IARU Region 1 to have MGMs
(machine generated modes) operating between 50.300 and 50.400.

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.)
N5JEH
 
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Re: New Digital mode commimg soon. FT8

Postby WB2FKO » Thu Jun 29, 2017 2:07 pm

Thanks Ed. Have you tried it yet? Is there any on-air activity with it? I will try to compile the code and play with it.
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Re: New Digital mode commimg soon. FT8

Postby WB2FKO » Fri Jun 30, 2017 12:32 am

OK I am up and running. Built it from source on Linux; took about 30 minutes. Can confirm that the developers are suggesting 6m frequency of 50.313 MHz for FT8 so will set it there and monitor.
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Re: New Digital mode commimg soon. FT8

Postby N5JEH » Fri Jun 30, 2017 6:34 am

I will have to wait until someone post it. I am not into compiling.
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Re: New Digital mode commimg soon. FT8

Postby WB2FKO » Fri Jun 30, 2017 9:44 am

Let it run all night and decoded about a half dozen stations when I checked. Beam pointed east. Heard K0TPP calling CQ and worked him. Band was in and out, very patchy propagation, so this mode worked well for that. Auto-sequence is essential as there is only a few seconds before next sequence starts, similar to MSK144. Band opened up but everybody is working JT65 still. I'm sure this FT8 mode will catch on.
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Re: New Digital mode commimg soon. FT8

Postby w7qq » Wed Jul 05, 2017 8:53 am

Great write-up Ed. This looks to be an exciting development.
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Re: New Digital mode commimg soon. FT8

Postby N5JEH » Thu Jul 06, 2017 8:14 am

For those of you using the new FT8 mode:



To: All WSJT-X users of FT8
From: WSJT Development Team
Subject: IMPORTANT NOTICE ABOUT EXPERIMENTAL MODE FT8

Thanks to all alpha testers who have sent us helpful information on
their experiences with FT8. The mode is basically working well, but
we've determined that we can improve it further by making a change to
the protocol that is not backward compatible.

Therefore, until further notice: DO NOT USE FT8 MODE IN CODE REVISIONS
LATER THAN r7782. In a few days we will issue another notice saying
that the protocol change is complete and tested. After that time you
must stop using FT8 mode in revisions r7782 and earlier. EVERYONE USING
FT8 MUST THEN UPGRADE TO A NEW CODE REVISION WITH A NUMBER TO BE SPECIFIED.

For those not building WSJT-X by themselves: We will plan to release
WSJT-X v1.8-rc1 very soon after the protocol change. This release will
include pre-built installation packages for Windows, Linux, and OS X.

-- 73, Joe, K1JT (for the WSJT Development Team)
N5JEH
 
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Re: New Digital mode commimg soon. FT8

Postby N5JEH » Fri Jul 07, 2017 10:32 am

Latest from K1JT with information about use of FT8 mode.

To: Users of FT8
From: WSJT Development Team
Subject: IMPORTANT NOTICE ABOUT EXPERIMENTAL MODE FT8

The planned protocol change in FT8 is now complete and tested. Effective
at 0000 UTC on July 8, 2017, you should stop using FT8 with any WSJT-X
code revision earlier than r7805.

If you are building WSJT-X for yourself from source code, on July 8 or
later you may upgrade to the latest code revision and recompile. You
will then have access to the latest version of FT8.

If you are waiting for pre-built installation packages: We plan to post
a release candidate for WSJT-X v1.8.0-rc1 configured for Windows, Linux,
and OS X very soon -- probably early next week. Thanks for your patience.

-- 73, Joe, K1JT (for the WSJT Development Team)
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Re: New Digital mode commimg soon. FT8

Postby WB2FKO » Wed Jul 12, 2017 12:39 am

The beta release of WSJT 1.8 is now out with the new FT8 mode. Can download as pre-compiled binaries/executables for your OS, so don't have to build from source anymore (unless you really want to). I have made about two dozen QSOs on 6m with the alpha version using single hop Es. It seems well-suited for the patchy, marginal openings that often occur on 6m. You can get the QSO done in under a minute with the expected ultra-high reliability. I suspect it will be superior to CW for all but the most fleeting, short-lived propagation paths. I also hope it puts JT65 out of business for terrestrial QSOs. Four minutes minimum for a few extra dB is just not worth it, especially in a contest or when the opening is short. Would be interested to hear the experiences of others.
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Re: New Digital mode commimg soon. FT8

Postby N5JEH » Wed Jul 12, 2017 6:50 pm

Working great here. Wish we had it for the EU openings. Maybe next year. Most EU operators still clinging to JT65A.
Also I is becoming the software release of the day again. As of 6:45 pm July 12 2017 the new release is 7847.
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