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Editing of new FST4/FST4W text in the User Guide.

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Joe Taylor 2020-09-24 10:42:39 -04:00
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49
doc/user_guide/en/introduction.adoc
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@ -17,25 +17,27 @@ encoding. JT65 and QRA64 were designed for EME ("`moonbounce`") on
the VHF/UHF bands and have also proven very effective for worldwide
QRP communication on the HF bands. QRA64 has some advantages over
JT65, including better performance for EME on the higher microwave
bands. JT9 was originally designed for the HF and lower
bands. Its submode JT9A is nearly 2 dB more sensitive than JT65 while using
less than 10% of the bandwidth. JT4 offers a wide variety of tone
spacings and has proven highly effective for EME on microwave bands up
to 24 GHz. These four "`slow`" modes use one-minute timed sequences
of alternating transmission and reception, so a minimal QSO takes four
to six minutes — two or three transmissions by each station, one
sending in odd UTC minutes and the other even. FT8 is operationally
similar but four times faster (15-second T/R sequences) and less
sensitive by a few dB. FT4 is faster still (7.5 s T/R sequences) and
especially well-suited for radio contesting. FST4 was added to
_WSJT-X_ in version 2.3.0. It is intended especially for use on the
LF and MF bands; further details can be found in the following
section, <<NEW_FEATURES,New Features in Version 2.3.0>>.
On the HF bands, world-wide QSOs are possible with any of these modes
using power levels of a few watts (or even milliwatts) and compromise
antennas. On VHF bands and higher, QSOs are possible (by EME and
other propagation types) at signal levels 10 to 15 dB below those
required for CW.
bands. JT9 was originally designed for the HF and lower bands. Its
submode JT9A is 1 dB more sensitive than JT65 while using less than
10% of the bandwidth. JT4 offers a wide variety of tone spacings and
has proven highly effective for EME on microwave bands up to 24 GHz.
These four "`slow`" modes use one-minute timed sequences of
alternating transmission and reception, so a minimal QSO takes four to
six minutes — two or three transmissions by each station, one sending
in odd UTC minutes and the other even. FT8 is operationally similar
but four times faster (15-second T/R sequences) and less sensitive by
a few dB. FT4 is faster still (7.5 s T/R sequences) and especially
well-suited for radio contesting. FST4 was added to _WSJT-X_ in
version 2.3.0. It is intended especially for use on the LF and MF
bands, and already during its first few months of testing
intercontinental paths have been spanned many times on the 2200 and
630 m bands. Further details can be found in the following section,
<<NEW_FEATURES,New Features in Version 2.3.0>>. On the HF bands,
world-wide QSOs are possible with any of these modes using power
levels of a few watts (or even milliwatts) and compromise antennas.
On VHF bands and higher, QSOs are possible (by EME and other
propagation types) at signal levels 10 to 15 dB below those required
for CW.
*ISCAT*, *MSK144*, and optionally submodes *JT9E-H* are "`fast`"
protocols designed to take advantage of brief signal enhancements from
@ -63,10 +65,11 @@ sequences they can be decoded at signal-to-noise ratios as low
as -31 dB in a 2500 Hz bandwidth. *FST4W* is designed for
similar purposes, but especially for use on LF and MF bands.
It includes optional sequence lengths as long as 30 minutes and
reaches sensitivity tresholds as low as -45 dB. WSPR and FST4W users
with internet access can automatically upload reception reports to a
central database called {wsprnet} that provides a mapping facility,
archival storage, and many other features.
reaches sensitivity tresholds as low as -45 dB. Users
with internet access can automatically upload WSPR and FST4W
reception reports to a central database called {wsprnet} that
provides a mapping facility, archival storage, and many other
features.
*Echo* mode allows you to detect and measure your own station's echoes
from the moon, even if they are far below the audible threshold.

17
doc/user_guide/en/new_features.adoc
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@ -2,13 +2,16 @@
=== New in Version {VERSION}
_WSJT-X 2.3.0_ introduces *FST4* and *FST4W*, new digital protocols
designed particularly for the LF and MF bands. On these bands their
fundamental sensitivities are better than other _WSJT-X_ modes with the
same sequence lengths, approaching the theoretical limits for their
rates of information throughput. FST4 is optimized for two-way QSOs,
while FST4W is for quasi-beacon transmissions of WSPR-style messages.
FST4 and FST4W do not require the strict, independent time
synchronization and phase locking of modes like EbNaut.
designed particularly for the LF and MF bands. Decoders for these
modes can take advantage of the very small Doppler spreads present at
these frequencies, even over intercontinental distances. As a
consequence, fundamental sensitivities of FST4 and FST4W are better
than other _WSJT-X_ modes with the same sequence lengths, approaching
the theoretical limits for their rates of information throughput. The
FST4 protocol is optimized for two-way QSOs, while FST4W is for
quasi-beacon transmissions of WSPR-style messages. FST4 and FST4W do
not require the strict, independent phase locking and time
synchronization of modes like EbNaut.
The new modes use 4-GFSK modulation and share common software for
encoding and decoding messages. FST4 offers T/R sequence lengths of

22
doc/user_guide/en/protocols.adoc
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@ -14,11 +14,11 @@ Special cases allow other information such as add-on callsign prefixes
aim is to compress the most common messages used for minimally valid
QSOs into a fixed 72-bit length.
The information payloads for FST4, FT4, FT8, and MSK144 contain 77 bits.
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.
Information payloads for FST4, FT4, FT8, and MSK144 contain 77 bits.
The 5 additional bits are used to flag special message types used for
nonstandard callsigns, contest exchanges, FT8 DXpedition Mode, and a
few other possibilities. Full details have been published in QEX, see
{ft4_ft8_protocols}.
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
@ -54,11 +54,6 @@ 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 FST4, FT4, FT8, and MSK144 protocols use different lossless compression
algorithms with features that generate and recognize special messages
used for contesting and other special purposes. Full details have
been published in QEX, see {ft4_ft8_protocols}.
To be useful on channels with low signal-to-noise ratio, this kind of
lossless message compression requires use of a strong forward error
correcting (FEC) code. Different codes are used for each mode.
@ -76,16 +71,15 @@ _WSJT-X_ modes have continuous phase and constant envelope.
FST4 offers T/R sequence lengths of 15, 30, 60, 120, 300, 900, and
1800 seconds. Submodes are given names like FST4-60, FST4-120, etc.,
the appended numbers indicating sequence length in seconds. Message
payloads contain 77 bits, and a 24-bit cyclic redundancy check (CRC)
appended to create a 101-bit message-plus-CRC word. Forward error
the appended numbers indicating sequence length in seconds. A 24-bit
cyclic redundancy check (CRC) is appended to the 77-bit message
payload to create a 101-bit message-plus-CRC word. Forward error
correction is accomplished using a (240,101) LDPC code. Transmissions
consist of 160 symbols: 120 information-carrying symbols of two bits
each, interspersed with five groups of eight predefined
synchronization symbols. Modulation uses 4-tone frequency-shift
keying (4-GFSK) with Gaussian smoothing of frequency transitions.
[[FT4PRO]]
==== FT4

37
doc/user_guide/en/tutorial-example5.adoc
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@ -1,24 +1,23 @@
FST4 is is designed for making 2-way QSOs on the LF and MF bands. Do
not confuse it with FT4, which has a very different purpose! Most
on-screen controls, auto-sequencing, and other features behave in FST4
as in other modes. However, operating conventions on the 2200 and 630
m bands make it desirable to have additional user controls that set
the active frequency range for decoding. Spin boxes labeled *F Low*
and *F High* set lower and upper frequency limits for the FST4
decoder.
image::FST4_center.png[align="center"]
Decoding limits are marked by dark green angle-bracket symbols *< >* on
the Wide Graph frequency scale:
Do not confuse FST4 with FT4, which has a very different purpose!
FST4 is is designed for making 2-way QSOs on the LF and MF bands.
Operation with FST4 is similar to that with other _WSJT-X_ modes: most
on-screen controls, auto-sequencing, and other features behave in
familiar ways. However, operating conventions on the 2200 and 630 m
bands have made some additional user controls desirable. Spin boxes
labeled *F Low* and *F High* set lower and upper frequency limits used
by the FST4 decoder, and these limits are marked by dark green
angle-bracket symbols *< >* on the Wide Graph frequency scale:
image::FST4_Decoding_Limits.png[align="center"]
In general the specified range should be no larger than you need, since
detected transmissions in modes other than the selected FST4 sequence
length will be undecodable and will slow down the decoding process.
{empty} +
If *Single decode* on the the *File | Settings | General* tab is
checked, the decoding range is further limited to the *F Tol* range
around *Rx Freq*.
image::FST4_center.png[align="center"]
It's best to keep the decoding range fairly small, since QRM and
transmissions in other modes or sequence lengths will slow down the
decoding process (and of course will be undecodable). By checking
*Single decode* on the the *File | Settings | General* tab, you can
further limit the decoding range to the setting of *F Tol* on
either side of *Rx Freq*.

24
doc/user_guide/en/tutorial-example6.adoc
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@ -1,16 +1,18 @@
FST4W has significant advantages over WSPR for use on the 2200 and 630
m bands. As for WSPR, the default Rx Freq is 1500 Hz and F Tol is
100 Hz, so the active decoding range 1400 to 1600 Hz. However, for added
flexibility you can select different center frequencies and F Tol values.
We expect that usage conventions will soon be established for FST4 activity on 2200 and 630 m.
FST4W is used in the same way as WSPR, but FST4W has significant
advantages for use on the 2200 and 630 m bands. By default the
central *Rx Freq* is 1500 Hz and *F Tol* is 100 Hz, so the active
decoding range is 1400 to 1600 Hz. However, for added flexibility you
can select different center frequencies and *F Tol* values. We expect
that usage conventions will soon be established for FST4W activity on
2200 and 630 m.
A new drop-down control below F Tol offers a round-robin mode for
A new drop-down control below *F Tol* offers a round-robin mode for
scheduling FST4W transmissions:
image::FST4W_RoundRobin.png[align="center"]
If three operators agree in advance to select the options 1/3, 2/3,
and 3/3, for example, their FST4W transmissions will occur in a fixed
sequence with no two stations transmitting simultaneously. Sequence 1
is the first sequence after 00:00 UTC. For WSPR-like scheduling
behavior, you should select Random with this control.
If three operators agree in advance to select the options *1/3*,
*2/3*, and *3/3*, for example, their FST4W transmissions will occur in
a fixed sequence with no two stations transmitting simultaneously.
Sequence 1 is the first sequence after 00:00 UTC. For WSPR-like
scheduling behavior, you should select *Random* with this control.