A few more updates tothe User Guide, making it "minimally acceptable" for the GA release of v2.0.

doc/user_guide/en/decoder_notes.adoc

@@ -8,9 +8,9 @@ false decodes.
 
 For example: when you decide to answer a CQ, you already know your own
 callsign and that of your potential QSO partner.  The software
-therefore "`knows`" what to expect for 57 of the 72 message bits (28
-bits for each of two callsigns, 1 bit for message type) in the next
-received message.  The decoder's task can thus be reduced to
+therefore "`knows`" what might be expected for at least 57 message
+bits (28 for each of two callsigns, 1 or more for message type) in the
+next received message.  The decoder's task can thus be reduced to
 determining the remaining 15 bits of the message and ensuring that the
 resulting solution is reliable.
 

doc/user_guide/en/protocols.adoc

@@ -2,18 +2,20 @@
 === Overview
 
 All QSO modes except ISCAT use structured messages that compress
-user-readable information into fixed-length packets of 72 bits.  Each
-message consists of two 28-bit fields normally used for callsigns and
-a 15-bit field for a grid locator, report, acknowledgment, or 73.  An
-additional bit flags a message containing arbitrary alphanumeric text,
-up to 13 characters.  Special cases allow other information such as
-add-on callsign prefixes (e.g., ZA/K1ABC) or suffixes (e.g., K1ABC/P)
-to be encoded. The basic aim is to compress the most common messages
-used for minimally valid QSOs into a fixed 72-bit length.  The
-information payload in FT8 includes 3 additional bits (75 bits total).
-One of the added bits is used to flag special messages used by the
-DXpedition station in FT8 DXpedition Mode.  Uses for the remaining two
-bits are yet to be defined.
+user-readable information into fixed-length packets.  JT4, JT9, JT65,
+and QRA64 use 72-bit payloads.  Standard messages consist of two
+28-bit fields normally used for callsigns and a 15-bit field for a
+grid locator, report, acknowledgment, or 73.  An additional bit flags
+a message containing arbitrary free text, up to 13 characters.
+Special cases allow other information such as add-on callsign prefixes
+(e.g., ZA/K1ABC) or suffixes (e.g., K1ABC/P) to be encoded. The basic
+aim is to compress the most common messages used for minimally valid
+QSOs into a fixed 72-bit length.
+
+The information payload for 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.
 
 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
@@ -42,22 +44,16 @@ additional information is sent in place of the grid locator or by
 encoding additional information into some of the 6 million available
 slots mentioned above.
 
-As a convenience for sending directed CQ messages, the compression
-algorithm supports messages starting with `CQ AA` through `CQ ZZ`.
-These message fragments are encoded internally as if they were the
-callsigns `E9AA` through `E9ZZ`.  Upon reception they are converted
-back to the form `CQ AA` through `CQ ZZ`, for display to the user.
+As a convenience for sending directed CQ messages, the 72-bit
+compression algorithm supports messages starting with `CQ AA` through
+`CQ ZZ`.  These message fragments are encoded internally as if they
+were the callsigns `E9AA` through `E9ZZ`.  Upon reception they are
+converted back to the form `CQ AA` through `CQ ZZ`, for display to the
+user.
 
-The FT8 and MSK144 modes support a special feature allowing convenient
-transmission and acknowledgment of four-character grid locators, the
-required exchanges in most North American VHF contests.  With this
-Contest Mode enabled, _WSJT-X_ supports messages of the form `W9XYZ
-K1ABC R FN42` by converting the grid locator to that of its
-diametrically opposite point on Earth.  The receiving program
-recognizes a locator implying a distance greater than 10,000 km, does
-the reverse transformation, and inserts the implied "`R`".  Obviously,
-this mode should not be used on the HF bands or under other
-circumstances where world-wide propagation is possible.
+The new FT8 and MSK144 protocols use a different lossless compression
+algorithm with features to generate and recognize the special messages
+used for contesting and the like.  (More to come, here ...)
 
 To be useful on channels with low signal-to-noise ratio, this kind of
 lossless message compression requires use of a strong forward error
@@ -75,9 +71,9 @@ _WSJT-X_ modes have continuous phase and constant envelope.
 ==== FT8
 
 Forward error correction (FEC) in FT8 uses a low-density parity check
-(LDPC) code with 75 information bits, a 12-bit cyclic redundancy check
-(CRC), and 87 parity bits making a 174-bit codeword.  It is thus
-called an LDPC (174,87) code.  Synchronization uses 7×7 Costas arrays
+(LDPC) code with 77 information bits, a 14-bit cyclic redundancy check
+(CRC), and 83 parity bits making a 174-bit codeword.  It is thus
+called an LDPC (174,91) code.  Synchronization uses 7×7 Costas arrays
 at the beginning, middle, and end of each transmission.  Modulation is
 8-tone frequency-shift keying (8-FSK) at 12000/1920 = 6.25 baud.  Each
 transmitted symbol carries three bits, so the total number of channel
@@ -231,7 +227,7 @@ which the probability of decoding is 50% or higher.
 |===============================================================================
 |Mode |FEC Type |(n,k) | Q|Modulation type|Keying rate (Baud)|Bandwidth (Hz)
 |Sync Energy|Tx Duration (s)|S/N Threshold (dB)
-|FT8  |LDPC, r=1/2|(174,87)| 8| 8-FSK| 6.25 | 50.0 | 0.27| 12.6 | -21
+|FT8  |LDPC, r=1/2|(174,91)| 8| 8-FSK| 6.25 | 50.0 | 0.27| 12.6 | -21
 |JT4A |K=32, r=1/2|(206,72)| 2| 4-FSK| 4.375| 17.5 | 0.50| 47.1 | -23
 |JT9A |K=32, r=1/2|(206,72)| 8| 9-FSK| 1.736| 15.6 | 0.19| 49.0 | -27
 |JT65A |Reed Solomon|(63,12) |64|65-FSK| 2.692| 177.6 | 0.50| 46.8 | -25
@@ -329,13 +325,13 @@ For details see Table 4, below.
 
 ==== MSK144
 
-Standard MSK144 messages are structured in the same way as those in
-the slow modes, with 72 bits of user information.  Forward error
-correction is implemented by first augmenting the 72 message bits with
-an 8-bit cyclic redundancy check (CRC) calculated from the message
-bits. The CRC is used to detect and eliminate most false decodes at
-the receiver. The resulting 80-bit augmented message is mapped to a
-128-bit codeword using a (128,80) binary low-density-parity-check
+Standard MSK144 messages are structured in the same way as in FT8,
+with 77 bits of user information.  Forward error correction is
+implemented by first augmenting the 77 message bits with a 13-bit
+cyclic redundancy check (CRC) calculated from the message bits. The
+CRC is used to detect and eliminate most false decodes at the
+receiver. The resulting 90-bit augmented message is mapped to a
+128-bit codeword using a (128,90) binary low-density-parity-check
 (LDPC) code designed by K9AN specifically for this purpose.  Two 8-bit
 synchronizing sequences are added to make a message frame 144 bits
 long.  Modulation is Offset Quadrature Phase-Shift Keying (OQPSK) at
@@ -379,6 +375,6 @@ and your QSO partner ± 200 Hz.
 |JT9F     |K=32, r=1/2|(206,72)| 8| 9-FSK| 50.0 |  450  | 0.19| 1.700 
 |JT9G     |K=32, r=1/2|(206,72)| 8| 9-FSK|100.0 |  900  | 0.19| 0.850 
 |JT9H     |K=32, r=1/2|(206,72)| 8| 9-FSK|200.0 | 1800  | 0.19| 0.425 
-|MSK144   |LDPC       |(128,80)| 2| OQPSK| 2000 | 2400  | 0.11| 0.072 
+|MSK144   |LDPC       |(128,90)| 2| OQPSK| 2000 | 2400  | 0.11| 0.072 
 |MSK144 Sh|LDPC       |(32,16) | 2| OQPSK| 2000 | 2400  | 0.20| 0.020 
 |=====================================================================