[SADXA] Proposal for new MFSK submode

[Jim W]

The software developers are working on a new digital mode.  Here is some 
information about it that's been distributed today via another user 
group to which I belong.

73, Jim  W9FI


-------- Forwarded Message --------

The following is courtesy of Rick K1MU:

Version 2.3 of WSJT-X introduces a new family of digital modes we 
designate FST41 . These modes have a wide range of capabilities and 
potential applications. Their fundamental sensitivities are better than 
most older modes in WSJT-X and are close to the theoretical limits for 
the same information throughput rates. Particular target applications 
include▪ WSPR-like, quasi-beacon transmissions on LF and MF bands ▪ QSOs 
with very weak signals on the LF and MF bands ▪ EME on VHF and UHF bands 
with T/R sequences both shorter and longer than 60 s ... but other uses 
will surely be found, as well. We expect that FST4 will serve some of 
its intended purposes better than older modes in WSJT-X, and without the 
strict time- and frequency-locking requirements of modes such as EbNaut.

FST4 uses 4-GFSK modulation and offers T/R sequence lengths of 15, 30, 
60, 120, 300, 900, and 1800 s. Submodes A, B, C, and D provide different 
tone spacings, to allow for use with a variety of propagation types and 
Doppler spreads. Forward error correction uses a low density parity 
check (LDPC) code with 240 information and parity bits. Transmissions 
consist of a sequence of 120 information-carrying symbols (2 bits each) 
interspersed with 40 synchronizing symbols. The underlying message 
payloads contain either 77 bits (the standard payload for FT4, FT8, and 
MSK144) or 50 bits (the standard for quasi-beacon, WSPR-style messages). 
With WSPR-like messages the mode designation becomes FST4W and the A 
submode is always used. In all cases, message formats displayed to the 
user are the same as in the other 50-bit and 77-bit modes in WSJT-X


       73,

  Dave, AA6YQ

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