Re: [wsjt-devel] GMSK waveform generation details
> On Jul 17, 2019, at 07:33, Joe Taylor wrote: > > The second plot shows examples of FSK and GFSK versions of FT8, captured from > on-the-air signals. Congratulations, Joe. I’m watching 17m signals right now on FT4 and they are MUCH cleaner looking than what we’ve seen on FT8. Good neighbor policy in action! 73, Gary - AG0N ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
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 *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
Re: [wsjt-devel] GMSK waveform generation details
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 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
Re: [wsjt-devel] GMSK waveform generation details
Ps: And I don’t just mean the technical aspects but also program environment development. Joe’s technical docs on the Princeton site are a great start ... but will Joe and Princeton resources be around forever (mind you we hope so)... ? As many are aware 64-bit Windows compiles of WSJT-X are available on Joe’s Princeton site. Many have sought guidance as to how to do this as Greg Beam’s JTSDK for 64-bit for Windows is not about yet. Promotion and learning guides – on both programming, techniques (even how Joe takes the analogue sound and then extracts meaningful info... which is a skill-gap that I have) and howto’s on the WSJT-X site would go a long way to taking what some perceive as the “nuff-nuff” elementary but genuine inquiry out of this place People like Joe invented the whole techniques for doing this... and their skill and teaching guidance is essential. Training and technique docs contributed from this general pool of knowledge may develop even better resources (from this work) for our community and provides no greater ongoing legacy for our community ! Sent from Mail<https://go.microsoft.com/fwlink/?LinkId=550986> for Windows 10 From: Stephen Ireland Sent: Wednesday, July 17, 2019 11:06:40 PM To: WSJT software development Subject: Re: [wsjt-devel] GMSK waveform generation details 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 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. ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
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
Re: [wsjt-devel] GMSK waveform generation details
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 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. ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
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. ___ wsjt-devel mailing list wsjt-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/wsjt-devel
Re: [wsjt-devel] GMSK waveform generation details
Try Joe's presentation here http://dokufunk.org/upload/taylor.ppsx de Mike W9MDB On Wednesday, July 17, 2019, 04:47:20 AM CDT, 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 ___ 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
