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106 lines
5.1 KiB
Plaintext
106 lines
5.1 KiB
Plaintext
Alpha Release: WSJT-X Version 1.7
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---------------------------------
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Short list of new features
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--------------------------
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1. New modes: ISCAT, MSK144, QRA64.
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2. Newly implemented submodes: JT65B-C, JT9B-H (wide and fast).
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3. FT decoder replaces KV decoder for JT65; KVASD is no longer used.
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4. Improvements to JT4, JT9, and JT65 decoders.
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5. Multi-pass decoding for JT65 and WSPR.
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6. Many improvements to Rig Control.
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7. Improved convenience features for EME Doppler tracking.
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8. Multiple configurations can be saved and restored.
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9. Sample-file download facility.
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10. Optional auto-sequencing for "fast" modes.
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11. Power settings optionally remembered for Transmit and Tune on a
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band-by-band basis.
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New Modes
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---------
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1. MSK144 is intended for meteor scatter at 50 MHz and higher. It
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uses a low-density parity check code (LDPC) designed by Steve Franke,
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K9AN. The mode is a direct descendant of the now-defunct mode JTMSK,
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with a number of improvements for better performance on weak and short
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meteor pings. The effective character transmission rate is about 250
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cps, compared with 147 cps for FSK441. Like JT4, JT9, JT65, and
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QRA64, MSK144 uses strong forward error correction. Message decoding
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is all or nothing: partial decodes do not occur, and you will see
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little or no garbage on your screen.
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Standard MSK144 message frames are 72 ms long, compared with about 120
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ms for an equivalent FSK441 message. The MSK144 waveform allows
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coherent demodulation, allowing up to 3 dB better sensitivity. After
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QSO partners have exchanged callsigns, MSK144 can use even shorter
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messages, only 20 ms long. As in all the fast modes in WSJT-X, the 72
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ms (or 20 ms) messages are repeated without gaps for the duration of a
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transmission cycle. For most purposes we recommend a T/R cycle
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duration of 15 s, but 5 s and 10 s sequences are also supported.
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Short ("Sh") messages in MSK144 are intended primarily for 144 MHz and
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higher frequencies, where most pings are very short. These messages
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do not contain full callsigns; instead, they contain a hash of the two
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callsigns along with a report, acknowledgement, or 73. Short messages
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are fully decodable only by the station to whom they are addressed, as
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part of an ongoing QSO, because only then will the received hash match
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that calculated using the known strings for "My Call" and "DX Call".
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If you are monitoring someone else's QSO, you will not be able to
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decode its Sh messages.
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An MSK144 signal occupies the full bandwidth of a typical SSB
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transmitter, so transmissions are always centered at an offset of
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1500Hz. For best results, selectable or adjustable Rx and Tx filters
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should be set to provide the flattest possible response over at least
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300 - 2700 Hz. The maximum permissible frequency offset between you
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and your QSO partner is 200 Hz, and less is better.
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2. QRA64 is a intended for EME and other weak-signal use. Its
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internal code was designed by Nico Palermo, IV3NWV, and implemented in
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WSJT-X by K1JT. The protocol uses a "Q-ary Repeat Accumulate" code --
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along with LDPC, another one of the latest research areas in
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communication theory. The QRA64 code is inherently better than the
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Reed Solomon (63,12) code used in JT65, yielding already a 1.3 dB
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advantage. QRA64 uses a new synchronizing scheme based on a 7 x 7
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Costas array, so you will not see a bright sync tone at the lowest
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tone frequency. This change yields another 1.9 dB advantage.
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In most respects our implementation of QRA64 is operationally similar
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to JT65. QRA64 does not use two-tone shorthand messages, and it makes
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no use of a callsign database. Rather, additional sensitivity is
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gained by making use of "already known" information as a QSO
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progresses -- for example, when reports are being exchanged and you
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have already decoded both callsigns in a previous transmission. QRA64
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presently offers no message averaging capability, though that may be
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added. In our early tests, many EME QSOs have already been made using
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submodes QRA64A-E on bands from 144 MHz to 10 GHz.
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3. ISCAT is essentially the same as in recent versions of program WSJT.
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For details consult the WSJT User Guide:
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http://physics.princeton.edu/pulsar/K1JT/doc/wsjt/
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Program Setup
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-------------
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Many of the new program capabilities are enabled when you check
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"Enable VHF/UHF/Microwave features" on the Settings | General tab.
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For MSK144 mode, we suggest setting "T/R 15 s" and "F Tol 100 Hz".
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Check "Sh" to enable the use of short messages and "Auto Seq" for
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auto-sequencing. For QRA64 mode, set Tx and Rx frequencies to 1000
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Hz. We encourage you to check "Save all" when making tests, and to
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save any of the resulting .wav files that might help us to improve
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program performance or behavior, or to illustrate a problem that you
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identify.
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Final Comments
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--------------
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Remember that you are using a pre-release version of WAJT-X. We will
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be grateful for any and all reports from test users; these will surely
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help us to make further improvements to WSJT-X. The most helpful bug
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reports describe the problem clearly and include a complete recipe to
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reproduce it. Feature requests are also welcome. Send your reports
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to wsjtgroup@yahoogroups.com.
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