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Editorial work on parts of the User Guide related to FT4.

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This commit is contained in:
Joe Taylor 2019-06-17 15:47:47 -04:00
parent 396bf1a013
commit 393b595126
4 changed files with 17 additions and 19 deletions
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6
doc/user_guide/en/introduction.adoc
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@ -34,8 +34,10 @@ are possible (by EME and other propagation types) at signal levels 10
to 15 dB below those required for CW.
Note that even though their T/R sequences are short, FT4 and FT8 are
classified as slow modes because their message frames are sent
only once per transmission.
classified as slow modes because their message frames are sent only
once per transmission. All fast modes in _WSJT-X_ send their message
frames repeatedly, as many times as will fit into the Tx sequence
length.
*ISCAT*, *MSK144*, and optionally submodes *JT9E-H* are "`fast`"
protocols designed to take advantage of brief signal enhancements from

18
doc/user_guide/en/new_features.adoc
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@ -1,17 +1,11 @@
=== New in Version {VERSION}
For quick reference, here's a short list of features and capabilities
added to _WSJT-X_ since Version 2.0.1:
- New FT4 protocol, designed especially for radio contesting
* T/R sequence length 7.5 s
* Bandwidth 80 Hz
* Threshold sensitivity -17.5 dB
- Improvements to accessibility
The most important feature added to _WSJT-X_ since Version 2.0.1 is
the new *FT4 protocol*, designed especially for radio contesting. It
has T/R sequence length 7.5 s, bandwidth 80 Hz, and threshold
sensitivity -17.5 dB. Version 2.1.0 also has improvements to FT8
waveform generation, contest logging, rig control, the user interface,
and accessibility, as well as a number of bug fixes.
=== Documentation Conventions

9
doc/user_guide/en/protocols.adoc
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@ -13,9 +13,10 @@ aim is to compress the most common messages used for minimally valid
QSOs into a fixed 72-bit length.
The information payload for FT4, FT8, and MSK144 contains 77 bits.
The 5 additional bits are used to flag special message types used for
FT8 DXpedition Mode, contesting, nonstandard callsigns, and a few
other special types.
The 5 new bits added to the original 72 are used to flag special
message types signifying special message types used for FT8 DXpedition
Mode, contesting, nonstandard callsigns, and a few other
possibilities.
A standard amateur callsign consists of a one- or two-character
prefix, at least one of which must be a letter, followed by a digit
@ -76,7 +77,7 @@ Forward error correction (FEC) in FT4 uses a low-density parity check
called an LDPC (174,91) code. Synchronization uses four 4×4 Costas
arrays, and ramp-up and ramp-down symbols are inserted at the start
and end of each transmission. Modulation is 4-tone frequency-shift
keying with Gaussian smoothing of frequency transitions (4-GFSK). The
keying (4-GFSK) with Gaussian smoothing of frequency transitions. The
keying rate is 12000/576 = 20.8333 baud. Each transmitted symbol
conveys two bits, so the total number of channel symbols is 174/2 + 16
+ 2 = 105. The total bandwidth is 4 × 20.8333 = 83.3 Hz.

3
doc/user_guide/en/tutorial-example4.adoc
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@ -14,7 +14,8 @@ frequency limit is approximately 4000 Hz.
- Select *File | Open* and navigate to
+...\save\samples\FT4\000000_000002.wav+. The waterfall and Band
Activity window should look something like the following screen shots.
Most of the decoded messages use the *RTTY Roundup* message formats.
This sample file was recorded during a practice contest test session, so
most of the decoded messages use the *RTTY Roundup* message formats.
[[X15]]
image::ft4_waterfall.png[align="left",alt="Wide Graph Decode FT4"]