Additions to User Guide.

git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@7219 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
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Joe Taylor 2016-10-21 20:24:42 +00:00
parent c1d5531603
commit fff1caade2
6 changed files with 161 additions and 159 deletions

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@ -51,3 +51,38 @@ and your own preferences.
Smoothing the displayed spectrum over more than one bin can enhance
your ability to detect weak EME signals with Doppler spread more than
a few Hz.
[[CONTROLS_FAST]]
=== Fast Graph
Three sliders at the bottom of the Fast Graph window can be used to
optimize gain and zero-offset of the displayed information. Hover the
mouse over a control to display a tip reminding you of its function.
Clicking the *Auto Level* button will produce reasonable settings
as a starting point. The waterfall palette used on this graph is
the same as the one selected on the Wide Graph.
image::fast-graph-controls.png[align="center",alt="Fast Graph Controls"]
[[CONTROLS_ECHO]]
=== Echo Graph
Controls at the bottom of the Echo Graph
- *Bins/Pixel* controls the displayed frequency resolution. Set this
value to 1 for the highest possible resolution, or to higher numbers
to compress the spectral display.
- *Gain* and *Zero* sliders control scaling and offset of plotted
spectra.
- *Smooth* values greater than 0 apply running averages to the plotted
spectra.
- Label *N* shows the number of echo pulses averaged.
- Click the *Colors* button to cycle through 6 possible choices of
color and line width for the plots.
image::echo-graph-controls.png[align="center",alt="EchoGraph Controls"]

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@ -1,106 +1,110 @@
[[JT65PRO]]
=== JT65
[[PROTOCOL_OVERVIEW]]
=== Overview
JT65 was designed for making minimal QSOs via EME ("`moon-bounce`") on
the VHF and UHF bands. A detailed description of the protocol and its
implementation in program _WSJT_ was published in {jt65protocol} for
September-October, 2005. Briefly stated, JT65 uses 60 s T/R sequences
and carefully structured messages. Standard messages are compressed so
that two callsigns and a grid locator can be transmitted in just 71
information bits. A 72^nd^ bit serves as a flag to indicate that a
message consists of arbitrary text (up to 13 characters) instead of
callsigns and a grid locator. Special formats allow other information
such as add-on callsign prefixes (e.g., ZA/K1ABC) or numerical signal
reports (in dB) to be substituted for the grid locator. The basic aim
is to compress the most common messages used for minimally valid QSOs
into a minimum fixed number of bits. After compression, a Reed Solomon
(63,12) error-control code converts 72-bit user messages into
sequences of 63 six-bit channel symbols.
JT65 requires tight synchronization of time and frequency between
transmitting and receiving stations. Each transmission is divided into
126 contiguous tone intervals or "`symbols`" of length 4096/11025 =
0.372 s. Within each interval the waveform is a constant-amplitude
sinusoid at one of 65 pre-defined frequencies. Frequency steps between
intervals are accomplished in a phase-continuous manner. Half of the
channel symbols are devoted to a pseudo-random synchronizing vector
interleaved with the encoded information symbols. The sync vector
allows calibration of time and frequency offsets between transmitter
and receiver. A transmission nominally begins at t = 1 s after the
start of a UTC minute and finishes at t = 47.8 seconds. The
synchronizing tone is at 11025 × 472/4096 = 1270.46 Hz, and is
normally sent in each interval having a “1” in the following
pseudo-random sequence:
100110001111110101000101100100011100111101101111000110101011001
101010100100000011000000011010010110101010011001001000011111111
Encoded user information is transmitted during the 63 intervals not
used for the sync tone. Each channel symbol generates a tone at
frequency 11025 × 472/4096 + 11025/4096 × (N+2) × m, where N is the
value of the six-bit symbol, 0 ≤ N ≤ 63, and m is 1, 2, or 4 for JT65
sub-modes A, B, or C. Sub-mode JT65A is always used at HF.
For EME (but, conventionally, not on the HF bands) the signal report
OOO is sometimes used instead of numerical signal reports. It is
conveyed by reversing sync and data positions in the transmitted
sequence. Shorthand messages for RO, RRR, and 73 dispense with the
sync vector entirely and use time intervals of 16384/11025 = 1.486 s
for pairs of alternating tones. The lower frequency is always 1270.46
Hz, the same as that of the sync tone, and the frequency separation is
110250/4096 = 26.92 Hz multiplied by n × m, with n = 2, 3, 4 for the
messages RO, RRR, and 73.
All QSO modes except ISCAT benefit from the use of structured
messages. Each such message consists of two 28-bit fields for
callsigns and a 15-bit field for a grid locator, report,
acknowledgment, or a "`73`" sign-off indicator. Alternatively, a
72^nd^ bit flags a message containing arbitrary alphanumeric text, up
to 13 characters. Special formats allow other information such as
add-on callsign prefixes (e.g., ZA/K1ABC) or suffixes (e.g., K1ABC/4)
to be encoded. The basic aim is to compress the most common messages
used for minimally valid QSOs into a fixed 72-bit length. To be
useful, this kind of lossless message compression requires use of a
strong forward error correcting (FEC) code. Different FEC codes are
used for each mode. These modes require good synchronization of time
and frequency between transmitting and receiving stations. As an aid
to the decoders, each protocol includes a "`synch vector`" of known
symbols along with the information-carrying symbols. Generated
waveforms for all of the _WSJT-X_ modes have continuous phase and
a constant envelope.
[[JT4PRO]]
=== JT4
JT4 uses 72-bit structured messages nearly identical to those in
JT65. Error control coding (ECC) uses a strong convolutional code with
constraint length K=32, rate r=1/2, and a zero tail, leading to an
encoded message length of (72+31) x 2 = 206 information-carrying
bits. Modulation is 4-tone frequency-shift keying at 11025 / 2520 =
FEC in JT4 uses a strong convolutional code with constraint length
K=32, rate r=1/2, and a zero tail. This choice leads to an encoded
message length of (72+31) x 2 = 206 information-carrying bits.
Modulation is 4-tone frequency-shift keying (4-FSK) at 11025 / 2520 =
4.375 baud. Each symbol carries one information bit (the most
significant bit) and ony synchronizing bit (the least signicifant
bit). The pseudo-random sync vector is the following sequence:
significant bit) and one synchronizing bit. The pseudo-random sync
vector is the following sequence:
000011000110110010100000001100000000000010110110101111101000
100100111110001010001111011001000110101010101111101010110101
011100101101111000011011000111011101110010001101100100011111
10011000011000101101111010
The two 32-bit polynomials used for convolutional encoding have
hexadecimal values f2d05351 and e4613c47.
[[JT9PRO]]
=== JT9
JT9 is designed for making minimally valid QSOs at LF, MF, and HF. It
uses 72-bit structured messages nearly identical (at the user level)
to those in JT65. Error control coding (ECC) uses a strong
convolutional code with constraint length K=32, rate r=1/2, and a zero
tail, leading to an encoded message length of (72+31) × 2 = 206
information-carrying bits. Modulation is nine-tone frequency-shift
keying, 9-FSK. Eight tones are used for data, one for
FEC in JT9 uses the same strong convolutional code aa JT4: constraint
length K=32, rate r=1/2, and a zero tail, leading to an encoded
message length of (72+31) × 2 = 206 information-carrying
bits. Modulation is nine-tone frequency-shift keying, 9-FSK at
12000.0/6912 = 1.736 baud. Eight tones are used for data, one for
synchronization. Eight data tones means that three data bits are
conveyed by each transmitted information symbol. Sixteen symbol
intervals are devoted to synchronization, so a transmission requires a
total of 206 / 3 + 16 = 85 (rounded up) channel symbols. The sync
symbols are those numbered 1, 2, 5, 10, 16, 23, 33, 35, 51, 52, 55,
60, 66, 73, 83, and 85 in the transmitted sequence. Each symbol lasts
for 6912 sample intervals at 12000 samples per second, or about 0.576
seconds. Tone spacing of the 9-FSK modulation is 12000/6912 = 1.736
Hz, the inverse of the symbol duration. The total occupied bandwidth
is 9 × 1.736 = 15.6 Hz.
60, 66, 73, 83, and 85 in the transmitted sequence. Tone spacing of
the 9-FSK modulation for JT9A is equal to the keying rate, 1.736 Hz.
The total occupied bandwidth is 9 × 1.736 = 15.6 Hz.
[[JT65PRO]]
=== JT65
A detailed description of the JT65 protocol was published in
{jt65protocol} for September-October, 2005. A Reed Solomon (63,12)
error-control code converts 72-bit user messages into sequences of 63
six-bit information-carrying symbols. These are interleaved with
another 63 symbols of synchronizing information according to the
following pseudo-random sequence:
100110001111110101000101100100011100111101101111000110101011001
101010100100000011000000011010010110101010011001001000011111111
The synchronizing tone is normally sent in each interval having a
"`1`" in the sequence. Modulation is 65-FSK at 11025/4096 = 2.692
baud. Frequency spacing between tones is equal to the keying rate for
JT65A, and 2 and 4 times larger for JT65B and JT65C. For EME QSOs the
signal report OOO is sometimes used instead of numerical signal
reports. It is conveyed by reversing sync and data positions in the
transmitted sequence. Shorthand messages for RO, RRR, and 73 dispense
with the sync vector entirely and use time intervals of 16384/11025 =
1.486 s for pairs of alternating tones. The lower frequency is the
same as that of the sync tone used in long messages, and the frequency
separation is 110250/4096 = 26.92 Hz multiplied by n for JT65A, with n
= 2, 3, 4 used to convey the messages RO, RRR, and 73.
[[QRA64_PROTOCOL]]
=== QRA64
TBD
Still to come ...
[[SLOW_SUMMARY]]
=== Slow Modes
[[PROTOCOL_SUMMARY]]
=== Comparison of Slow Modes
[[SLOW_TAB]]
.Parameters of Slow Modes
[width="90%",cols="3h,^3,^2,^1,^2,^2,^2,^2,^2,^2",frame=topbot,options="header"]
|===============================================================================
|Mode |FEC Type |(k,n) | Q| Mod | Baud |BW (Hz)|fSync|TxT (s)|S/N (dB)
|JT4A |K=32, r=1/2|(206,72)| 2| 4-FSK| 4.375| 17.5 | 0.50| 47.1 | -23
|JT9A |K=13, r=1/2|(206,72)| 8| 9-FSK| 1.736| 15.6 | 0.19| 49.0 | -27
|JT65A |RS |(63,12) |64|65-FSK| 2.692| 177.6 | 0.50| 46.8 | -25
|QRA64A|QRA |(63,12) |64|64-FSK| 1.736| 111.1 | 0.25| 48.4 | -28
| WSPR |K=32, r=1/2|(162,50)| 2| 4-FSK| 1.465| 5.9 | 0.50|110.6 | -29
|===============================================================================
Frequency spacing between tones, total occupied bandwidth, and
approximate decoding thresholds are given for the various submodes of
JT4, JT9, and JT65 in the following table:
approximate threshold signal-to-noise ratios are given for the various
submodes of JT4, JT9, JT65, and QRA64 in the following table:
Submode Spacing BW S/N
(Hz) (Hz) dB
@ -125,28 +129,16 @@ JT4, JT9, and JT65 in the following table:
QRA64D 13.889 888.9
QRA64E 27.228 1777.8
Transmissions in all three modes are essentially the same length, and
all use 72 bits to carry message information. At user level the modes
support nearly identical message structures.
JT4 and JT65 signal reports are constrained to the range 1 to 30
dB. This range is more than adequate for EME purposes, but not enough
for optimum use at HF. S/N values displayed by the JT4 and JT65
decoders are clamped at an upper limit 1 dB, and the S/N scale is
nonlinear above 10 dB.
By comparison, JT9 allows for signal reports in the range 50 to +49
dB. It manages this by taking over a small portion of "`message
space`" that would otherwise be used for grid locators within 1 degree
of the south pole. The S/N scale of the present JT9 decoder is
reasonably linear (although it's not intended to be a precision
measurement tool).
JT9 is an order of magnitude better than JT65 in spectral
efficiency. On a busy HF band, the conventional 2-kHz-wide JT65
sub-band is often filled with overlapping signals. Ten times as many
JT9 signals can fit into the same frequency range, without collisions.
decoders are clamped at an upper limit 1 dB, and the S/N scale
becomes significantly nonlinear above 10 dB. JT9 allows signal
reports in the range 50 to +49 dB. It manages this by taking over a
small portion of "`message space`" that would otherwise be used for
grid locators within 1 degree of the south pole. The S/N scale of the
present JT9 decoder is reasonably linear (although it's not intended
to be a precision measurement tool).
=== ISCAT
@ -190,74 +182,44 @@ many times as will fit into a Tx sequence.
=== MSK144
(this section needs work ...)
MSK144 is intended for meteor-scatter QSOs on the VHF bands. Standard
messages are structured in the same way as those in the slow modes,
with a 72 bits of user information. Forward error correction is
implemented by first augmenting the 72 message bits with an 8-bit 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 then mapped to a 128-bit codeword using a
(128,80) binary low-density-parity-check (LDPC) code designed
Standard MSK144 messages are structured in the same way as those in
the slow modes, with a 72 bits of user information. Forward error
correction is implemented by first augmenting the 72 message bits with
an 8-bit 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 (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 2000 baud. Even-numbered bits
are conveted over the in-phase channel, odd-numbered bits on the
are conveyed over the in-phase channel, odd-numbered bits on the
quadrature channel. Individual symbols are shaped with half-sine
profiles, thereby ensuring a generated waveform with constant
envelope, equivelent to a Minimum Shift Keying (MSK) waveform. Frame
duration is 72 ms so the effective character transmission rate for
standard messages is as high as 250 cps.
duration is 72 ms, so the effective character transmission rate for
standard messages is up to 250 cps.
MSK144 also supports short-form messages that can be used after QSO
partners have exchanged callsigns. These consist of 4 bits that
encode a signal report, R+report, RRR, or 73, together with a 12-bit
hash code based on the ordered pair of callsigns is use. A specially
designed LDPC (32,16) code provides error-correction, and an 8-bit
synchronizing vector is appended to make up a 40-bit frame.
Short-message duration is thus 20 ms, and short messages can be
conveyed by very short meteor "pings".
partners have exchanged both callsigns. Short messages consist of 4
bits encoding a signal report, R+report, RRR, or 73, together with a
12-bit hash code based on the ordered pair of "`to`" and "`from`"
callsigns. Another specially designed LDPC (32,16) code provides
error correction, and an 8-bit synchronizing vector is appended to
make up a 40-bit frame. Short-message duration is thus 20 ms, and
short messages can be decoded from very short meteor pings.
As in the other fast modes in WSJT-X, the 72 ms or 20 ms frames of
MSK144 messages are repeated without gaps for the full duration of a
transmission cycle. For most purposes, a cycle duration of 15s is
recommended for MSK144.
The 72 ms or 20 ms frames of MSK144 messages are repeated without gaps
for the full duration of a transmission cycle. For most purposes, a
cycle duration of 15 s is suitable and recommended for MSK144.
The modulated MSK144 signal occupies the full bandwidth of a SSB
transmitter, so transmissions are always centered on audio frequency
transmitter, so transmissions are always centered at audio frequency
1500 Hz. For best results, transmitter and receiver filters should be
adjusted to provide the flattest possible response over the range
300Hz to 2700Hz. Further, the maximum permissible frequency offset
between you and your QSO partner should be ± 100 Hz.
300Hz to 2700Hz. The maximum permissible frequency offset between you
and your QSO partner ± 200 Hz.
Details:
Standard 72ms MSK frames contain 144 bits and consist of a standard
JT-mode 72-bit message augmented with 56 bits for error detection and
correction. The 72+56=128-bit codeword is combined with two 8-bit sync
words to form a 144-bit frame. The frame is constructed as
S8,D48,S8,D80, where S8 represents an 8-bit sync word and D48,D80
represent the first 48 bits and last 80 bits of the 128-bit codeword,
respectively. (At present, the 128-bit codeword is re-ordered to put
even/odd bits at the beginning/end of the codeword — this is a
holdover from JTMSK and is probably not necessary.) The 144-bit frame
is repeated for the duration of a transmission cycle.
=== Summary
[[SLOW_TAB]]
.Parameters of Slow Modes
[width="90%",cols="3h,^3,^2,^1,^2,^2,^2,^2,^2,^2",frame=topbot,options="header"]
|===============================================================================
|Mode |FEC Type |(k,n) | Q| Mod | Baud |BW (Hz)|fSync|TxT (s)|S/N (dB)
|JT4A |K=32, r=1/2|(206,72)| 2| 4-FSK| 4.375| 17.5 | 0.50| 47.1 | -23
|JT9A |K=13, r=1/2|(206,72)| 8| 9-FSK| 1.736| 15.6 | 0.19| 49.0 | -27
|JT65A |RS |(63,12) |64|65-FSK| 2.692| 177.6 | 0.50| 46.8 | -25
|QRA64A|QRA |(63,12) |64|64-FSK| 1.736| 111.1 | 0.25| 48.4 | -28
| WSPR |K=32, r=1/2|(162,50)| 2| 4-FSK| 1.465| 5.9 | 0.50|110.6 | -29
|===============================================================================
=== Fast Modes
.Parameters of Fast Modes
[width="90%",cols="3h,^3,^2,^1,^2,^2,^2,^2,^2,^2",frame="topbot",options="header"]

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@ -116,7 +116,7 @@ averaging* over successive transmissions and/or correlation decoding,
image::decoding_depth.png[align="center",alt="Decoding Depth"]
IMPORTANT: Additional hints for using JT4 and Echo mode on the
EME path have been compiled by G3WDG and are available here: {jt4eme}.
*EME path have been compiled by G3WDG and are available here: {jt4eme}.
=== JT65
@ -142,6 +142,14 @@ _WSJT-X_, Version 1.7. The protocol is still subject to change, and
some features of the decoder will likely change. In most ways
operation of QRA64 is similar to JT65.
=== ISCAT
ISCAT is a useful mode for signals that are weak but more or less
steady in amplitude, at least for several seconds. Aircraft scatter
at 10 GHz is a good example. ISCAT messages are free-format and may
have any length from 1 to 28 characters. The protocol includes no
error-correction facility.
=== MSK144
Meteor-scatter QSOs can be made any time on the VHF bands at distances
@ -199,10 +207,6 @@ IMPORTANT: There is little or no advantage to using MSK144 *Sh*
messages at 50 or 70 MHz. At these frequencies most pings are long
enough to support standard messages.
=== Scatter Propagation with ISCAT
TBD ...
=== Echo Mode
*Echo* mode allows you to make sensitive measurements of your own

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@ -148,10 +148,6 @@ include::wspr.adoc[]
[[COMMAND_REF]]
== On-Screen Controls
[[CONTROLS_WIDE]]
=== Wide Graph
include::controls-functions-wide-graph.adoc[]
[[CONTROLS_MAIN]]
=== Main Window
include::controls-functions-main-window.adoc[]
@ -176,6 +172,10 @@ include::controls-functions-status-bar.adoc[]
=== Menus
include::controls-functions-menus.adoc[]
[[CONTROLS_WIDE]]
=== Wide Graph
include::controls-functions-wide-graph.adoc[]
[[LOGGING]]
== Logging
include::logging.adoc[]
@ -201,19 +201,20 @@ include::protocols.adoc[]
== Astronomical Data
include::astro_data.adoc[]
////
[[TXRX]]
== Implementation Details
include::implementation.adoc[]
////
[[TROUBLE_SHOOTING]]
== Troubleshooting
To be added (?) ...
////
[[UTIL]]
== Utility Programs
include::utilities.adoc[]
////
[[SUPPORT]]
== Support