mirror of
https://github.com/saitohirga/WSJT-X.git
synced 2025-10-30 20:40:28 -04:00
35 lines
1.8 KiB
Plaintext
35 lines
1.8 KiB
Plaintext
[[NEW_FEATURES]]
|
|
=== New in Version {VERSION}
|
|
|
|
_WSJT-X 2.3.0_ introduces *FST4* and *FST4W*, new digital protocols
|
|
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
|
|
15, 30, 60, 120, 300, 900, and 1800 seconds, while FST4W omits the
|
|
lengths shorter than 120 s. Submodes are given names like FST4-60,
|
|
FST4W-300, etc., the appended numbers indicating sequence length in
|
|
seconds. Message payloads contain either 77 bits, as in FT4, FT8, and
|
|
MSK144, or 50 bits for the WSPR-like messages of FST4W. Message
|
|
formats displayed to the user are like those in the other 77-bit and
|
|
50-bit modes in _WSJT-X_. Forward error correction uses a low density
|
|
parity check (LDPC) code with 240 information and parity bits.
|
|
Transmissions consist of 160 symbols: 120 information-carrying symbols
|
|
of two bits each, interspersed with five groups of eight predefined
|
|
synchronization symbols.
|
|
|
|
*We recommend that on the 2200 and 630 m bands FST4 should replace JT9
|
|
for making 2-way QSOs, and FST4W should replace WSPR for propagation
|
|
tests*. Operating conventions on these LF and MF bands will
|
|
eventually determine the most useful T/R sequence lengths for each
|
|
type of operation.
|