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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/URORHV24WQC5GGGT5CXUQ4WUVXDH7WVJ/?format=api",
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    "message_id": "[email protected]",
    "message_id_hash": "URORHV24WQC5GGGT5CXUQ4WUVXDH7WVJ",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/N2SBAS2FMVGSLUNSXK4GQJLWJ3EUHIF3/?format=api",
    "sender": {
        "address": "daniel (a) destevez.net",
        "mailman_id": "c2eac82b839b45f5a7d3b923c1721007",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/c2eac82b839b45f5a7d3b923c1721007/emails/?format=api"
    },
    "sender_name": "Dani EA4GPZ",
    "subject": "Re: [amsat-bb] LilacSat-1 and Codec2",
    "date": "2017-05-29T09:04:31Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/N2SBAS2FMVGSLUNSXK4GQJLWJ3EUHIF3/?format=api",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "El 28/05/17 a las 05:25, Tom Schuessler escribió:\n> OK I'm NOT a Linux guy.  Let's see if we can do LilacSat-1 for the rest of\n> us.\n> \n> What I have been able to figure out is that Codec2 is a digital voice codec\n> that creates audio speech out of some input data.  If I read things right,\n> LilacSat-1's concept here is to take analog FM (PL tone of 67HZ to open it's\n> squelch), input and digitize the audio and then encode what it hears to\n> digital data using the Codec2 process.  That data is transmitted on a 9600\n> data stream BPSK decoded by an application.  I think that is a good basic\n> explanation of the system.  A unique concept.\n\nHi Tom,\n\nYour understanding is almost correct. To be precise, LilacSat-1 has an\nSDR, so RF is digitized and then FM demodulation is done digitally (on\nan ARM processor, I think).\n\n> Now back to not being a Linux person.  I see the posts on the BB dealing\n> with folks using GNU radio to decode the data.  GNU Radio which is a Linux\n> Digital voice program apparently can be ported to Windows, but the install\n> process is very touchy feely.  My looking at pages about Codec2 I get\n> references to the \"FreeDV\" program.  I found they do have a Windows\n> installer for FreeDV.  Is that the accepted program for this purpose using\n> CODEC2?  After installing the FreeDV program, I see that there are different\n> flavors of the Codec it uses, but only some of them seem to match what is\n> noted as flavors on the Codec2 development page.  Which actual flavor is the\n> LilacSat-1 system using?\n\nCodec2 is an open-source audio codec which was developed because all the\nother low bitrate codecs that one can use for radio are covered by\npatents. It is used in FreeDV, which is a complete solution (digital\nvoice mode) for HF (and a mode for VHF/UHF is now in development).\n\nFreeDV and LilacSat-1 use the same codec, but other than that, the rest\n(the modem) is different.\n\nThe Codec2 variant used in LilacSat-1 is Codec2 1300bps, which is the\nsame that is used in FreeDV 1600. LilacSat-1 uses 9600baud BPSK and FEC\nfollowing the CCSDS standard. It uses custom framing to multiplex the\ndigital voice with telemetry and the image downlink. FreeDV 1600 uses\nmulticarrier BPSK/QPSK at a total of 1600bps.\n\nSo the FreeDV software can't be used for LilacSat-1.\n\nCurrently, the only solutions to receive LilacSat-1 involve GNU Radio.\nYou have a decoder in gr-lilacsat\n\nhttps://github.com/bg2bhc/gr-lilacsat\n\nwhich was developed by Wei BG2BHC (he is in the satellite team) and\nanother in gr-satellites which I developed\n\nhttps://github.com/daniestevez/gr-satellites\n\nProbably it's easier to get up and running gr-lilacsat, but the decoder\nin gr-satellites has some extra features.\n\n> I intend to give this a listen sometime this long weekend to see if I can\n> decode anything.  Should be interesting. Does anyone have raw downlink data\n> samples that I could use to test what the FreeDV program can \"hear\"?\n\nYou have a sample here:\n\nhttps://github.com/daniestevez/satellite-recordings\n\n\n73,\n\nDani EA4GPZ\n\n\n",
    "attachments": []
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