Bill, Thanks for this constructive guidance; not just 10 minutes ago I had an inexperienced Amateur ask me this very same question. As someone that has had considerable involvement myself in the research and coding of such systems from “unspeakable applications” I was half-way into a constructive, advancing similar response.
I will advise the inquisitor to seek out Steve K9AN’s work as it becomes available. I have forwarded your post to them 😊 As a constructive, developmental and learning suggestion (which AR is all about) perhaps technological guidance (and learning) resources could be attached and maintained via the Sourceforge (or other) delivery pages so as you folks do not get the “Thomas Crappers” pestered out of you folks on core developmental sites for guidance? 73 Steve I VK3VM/VK3SIR Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10 ________________________________ From: Bill Somerville <g4...@classdesign.com> Sent: Wednesday, July 17, 2019 10:54:11 PM To: wsjt-devel@lists.sourceforge.net Subject: Re: [wsjt-devel] GMSK waveform generation details On 17/07/2019 09:09, 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. I will try to install the new release this evening. Many thanks Conrad PA5Y Hi Conrad, I believe Steve, K9AN, is writing up a short paper on the FT8 and FT4 modulation details aimed particularly at 3rd party implementers who wish to generate equivalent waveforms. GMSK is a modification of the MSK waveform by smoothing the frequency shifts, in WSJT-X we generate the whole message waveform in advance rather than the instantaneous calculations we use for MFSK signals to generate the phase angle and hence the instantaneous value of each sample. If you have the skills then the implementations are here: https://sourceforge.net/p/wsjt/wsjtx/ci/master/tree/lib/ft8/gen_ft8wave.f90 and here: https://sourceforge.net/p/wsjt/wsjtx/ci/master/tree/lib/ft4/gen_ft4wave.f90 Note that the FT4 waveform includes a start and end padding to allow for ramp up and down and to accommodate the overhang from the Gaussian smoothing, the final FT8 waveform does not include this padding as it has to remain compatible with the old MFSK FT8 waveform. 73 Bill G4WJS.
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