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110 lines
5.2 KiB
Plaintext
110 lines
5.2 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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New Modes
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---------
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1. MSK144 is intended for meteor scatter at 50 MHz and higher.
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Designed and tested by K9AN and K1JT, it uses a low-density parity
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check code (LDPC) -- one of the latest-and-greatest areas of active
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research in communication theory.
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MSK144 is a direct descendant of the now-defunct mode JTMSK, with a
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number of improvements for better performance on weak and short meteor
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pings. The effective character transmission rate is about 250 cps,
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compared with 147 cps for FSK441 and 154 cps for JTMSK. Like JT4,
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JT9, JT65, and JTMSK, MSK144 uses strong forward error correction, so
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message decoding is essentially "all or nothing". You will see little
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or no garbage on your screen.
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Standard MSK144 message frames are 72 ms long, compared to 117 ms for
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JTMSK. The MSK144 waveform allows coherent demodulation, allowing up
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to 3 dB better sensitivity. After QSO partners have exchanged
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callsigns, MSK144 can use even shorter messages, only 20 ms long. As
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in all the fast modes in WSJT-X, the 20 ms or 72 ms messages are
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repeated without gaps for the duration of a transmission cycle. For
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most purposes we recommend a T/R cycle duration of 15 s, but 5 s and
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10 s sequences are also supported.
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Short ("Sh") messages in MSK144 are intended primarily for 144 MHz,
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where most pings are short. These messages do not contain full
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callsigns; instead, they contain a hash of the entire transmitted
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message along with a report. They are not encrypted -- the report is
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sent in the clear along with the hash. Short messages are fully
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decodable only by the station to whom they are addressed, as part of
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an ongoing QSO, because only then will the received hash match that
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calculated using the known strings for "My Call" and "DX Call" and the
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received report, RRR, or 73. If you are monitoring someone else's
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QSO, you will not be able to 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/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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another one of the latest research areas in communication theory. The
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QRA64 code is inherently better than the Reed Solomon (63,12) code
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used in JT65, yielding already a 1.3 dB advantage. QRA64 uses a new
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synchronizing scheme based on a 7 x 7 Costas array, so you will not
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see a bright sync tone at the lowest tone frequency. This change
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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 an Alpha Release. We will be grateful for
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any and all reports from test users that may help us to further
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improve WSJT-X. The most helpful reports describe the problem clearly
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and include a complete recipe to reproduce it. Send your reports to
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wsjtgroup@yahoogroups.com.
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Please be patient concerning responses from the development group.
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Several of us will be on vacation or otherwise engaged during much of
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August.
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