Thanks, hadn't seen it. I'm afraid it's a little over my head right now. Adrian
On April 2, 2018 1:08:35 PM UTC, Anon Lister <listera...@gmail.com> wrote: >I don't know if you saw his presentation but Andy Walls did a talk on >the >new clock recovery block he wrote to address issues he had with >existing >ones. I believe it's in tree now? > >https://www.gnuradio.org/wp-content/uploads/2017/12/Andy-Walls-Samples-to-Digital-Symbols.pdf > >On Mon, Apr 2, 2018, 08:55 Adrian Musceac <kanto...@gmail.com> wrote: > >> I should add that the main problem I face is getting it synchronized >fast >> enough for short bursts. >> >> Adrian >> >> On April 2, 2018 11:54:21 AM UTC, Thomas Habets <tho...@habets.se> >wrote: >>> >>> I just seem to recall that being said. >>> >>> I've used M&M successfully in the past, but it does require some >>> massaging of the data to not be "square wave" before it'll work. >Also does >>> it work (well) for M-FSK? >>> >>> On 2 April 2018 at 11:16, Adrian Musceac <kanto...@gmail.com> wrote: >>> >>>> Hi, >>>> >>>> Why is the M&M algorithm discouraged? >>>> I use successfully both in FSK and PSK demodulators. It seems to >perform >>>> fine. >>>> >>>> Regards, >>>> Adrian >>>> >>>> >>>> On April 2, 2018 8:48:00 AM UTC, Thomas Habets <tho...@habets.se> >wrote: >>>>> >>>>> Hi. >>>>> >>>>> As an experiment I'm trying to decode an FT8 signal I've captured. >I've >>>>> gotten far enough that I can clearly see the packet ( >>>>> https://blog.habets.se/tmp/ft8_packet.png), but now I want to >actually >>>>> turn that into bits. >>>>> >>>>> I know it's 8FSK (the above screenshot is quad demod of that), but >I >>>>> have a few questions on clock recovery: >>>>> >>>>> * Is the GFSK block only for BFSK? If so then that's out. >>>>> * Is there a "best" clock recovery block nowadays? I seem to >recall >>>>> "Clock Recovery MM" being discouraged in favor of "Polyphase Clock >Sync". >>>>> * I'm trying to read up on the parameters Polyphase Clock Sync >wants, >>>>> but any pointers would be helpful. >>>>> * Would it be a good idea to throw in a costas loop for frequency >>>>> tuning? >>>>> * Does Polyphase Clock Sync have the same dislike of "staircase" >>>>> inputs? That is, I should try to make the center of the bits more >"pointy"? >>>>> (e.g. lowpass filter them) >>>>> >>>>> I've done some custom OOT decoders before, so I'm not shy about >that. >>>>> Maybe the best thing is some whole-packet clock recovery[1]. But >if I just >>>>> write a block that takes the quad demod (see above screenshot) and >finds >>>>> the "platforms", outputting a message that is a list of floats, >and then >>>>> another block that takes a list of floats and the number 8 and >decodes it >>>>> as 8FSK, well it seems like I may be reimplementing things where >I'm >>>>> guessing someone might say "oh just use this block". >>>>> >>>>> Also for experimentation and my own understanding I'd like to turn >it >>>>> into bits using in-tree blocks, if possible. >>>>> >>>>> Maybe a correct Polyphase Clock Sync of the quad demod followed by >a >>>>> Constellation decoder? I could use the float as the phase, with >magnitude >>>>> 1. Does that make sense? Is it a good idea? >>>>> >>>>> What I have so far is: >>>>> Data: >>>>> https://blog.habets.se/tmp/ft8-burst-10k.raw (10k samp_rate) >>>>> >>>>> GRC: >>>>> https://blog.habets.se/tmp/ft8_decode.grc >>>>> >>>>> Screenshot: >>>>> https://blog.habets.se/tmp/ft8_decode_grc.png >>>>> (everything off-screen to the right is failed clock recovery >>>>> experiments) >>>>> >>>>> Quad demod >>>>> https://blog.habets.se/tmp/ft8_packet.png >>>>> >>>>> >>>>> [1] Like https://www.youtube.com/watch?v=rQkBDMeODHc which I >turned >>>>> into >>>>> >https://github.com/ThomasHabets/radiostuff/blob/master/gr-habets/python/magic_decoder.py >>>>> >>>>> -- >>>>> typedef struct me_s { >>>>> char name[] = { "Thomas Habets" }; >>>>> char email[] = { "tho...@habets.se <tho...@habets.pp.se>" }; >>>>> char kernel[] = { "Linux" }; >>>>> char *pgpKey[] = { "http://www.habets.pp.se/pubkey.txt"; }; >>>>> char pgp[] = { "9907 8698 8A24 F52F 1C2E 87F6 39A4 9EEA 460A >0169" }; >>>>> char coolcmd[] = { "echo '. ./_&. ./_'>_;. ./_" }; >>>>> } me_t; >>>>> >>>> >>>> _______________________________________________ >>>> Discuss-gnuradio mailing list >>>> Discuss-gnuradio@gnu.org >>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>>> >>>> >>> >>> >>> -- >>> typedef struct me_s { >>> char name[] = { "Thomas Habets" }; >>> char email[] = { "tho...@habets.se <tho...@habets.pp.se>" }; >>> char kernel[] = { "Linux" }; >>> char *pgpKey[] = { "http://www.habets.pp.se/pubkey.txt"; }; >>> char pgp[] = { "9907 8698 8A24 F52F 1C2E 87F6 39A4 9EEA 460A 0169" >}; >>> char coolcmd[] = { "echo '. ./_&. ./_'>_;. ./_" }; >>> } me_t; >>> >> _______________________________________________ >> Discuss-gnuradio mailing list >> Discuss-gnuradio@gnu.org >> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>
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