| Remarkably GSM uses GMSK -N2LO~> -----Original Message----- From: g0...@g0ruz.com To: wsjt-devel@lists.sourceforge.net Sent: 2019-07-17 11:49:12 AM Subject: Re: [wsjt-devel] GFSK waveform generation details Of course the typo was mine originally. I have changed the title.
73
Conrad From: Joe Taylor <j...@princeton.edu>
Sent: 17 July 2019 17:06 To: WSJT software development Subject: Re: [wsjt-devel] GMSK waveform generation details One final point, and correcting a typo in my previous message.
The Subject line should read GFSK, not GMSK. FT4 and FT8 use Gaussian Frequency Shift Keying (GFSK), *not* Gaussian Minimum Shift Keying (GMSK). The latter is yet another possible modulation scheme. -- Joe, K1JT On 7/17/2019 10:27 AM, Conrad PA5Y wrote: > Thanks both Bill and Joe, that is certainly a very worthwhile > improvement, thanks to the team for the effort! I will read everything > with interest. > > > Regards > > > Conrad PA5Y > > > > ------------------------------------------------------------------------ > *From:* Joe Taylor <j...@princeton.edu> > *Sent:* 17 July 2019 15:33 > *To:* WSJT software development > *Subject:* Re: [wsjt-devel] GMSK waveform generation details > Hi Conrad, > > On 7/17/2019 4:09 AM, Conrad PA5Y wrote: >> Hello Joe I am quite interested to learn more about the GMSK waveform >> generation, where can I read more about it and the implementation in >> WSJT-X and the advantages. > > A good place to start would be our document describing FT4 during its > early development, especially pages 3 and 4: > > http://physics.princeton.edu/pulsar/k1jt/FT4_Protocol.pdf > > Bill gave you pointers to the code that generates GMSK waveforms for FT4 > and FT8. > > Main advantages: > > - constant envelope waveform, > - peak-to-average power ratio = 1.0 > - very clean spectrum > > Plots of spectral measurements you may find interesting: > > http://physics.princeton.edu/pulsar/k1jt/rtty_ft8_ft4_spec.png > http://physics.princeton.edu/pulsar/k1jt/FT8_FSK_GFSK.png > > For comparison, the first plot shows spectra of a standard RTTY signal, > FT8 as generated with WSJT-X 2.0, FT8 with WSJT-X 2.1, and FT4. > > The second plot shows examples of FSK and GFSK versions of FT8, captured > from on-the-air signals. The signals happen to have nearly identical > strengths. The much cleaner spectrum of the new FT8 is easy to see on > the waterfall as well as the graphed spectrum. > > -- 73, Joe, K1JT > > > _______________________________________________ > wsjt-devel mailing list > wsjt-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/wsjt-devel > > > _______________________________________________ > wsjt-devel mailing list > wsjt-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/wsjt-devel > _______________________________________________ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel |
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