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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/XWN22VY44WRV3JUDWR7XAP3UILRVF36D/",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/",
    "message_id": "[email protected]",
    "message_id_hash": "XWN22VY44WRV3JUDWR7XAP3UILRVF36D",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/5HCWDGY7NTFKXMOTF2O7KEJMGKDL6VW4/",
    "sender": {
        "address": "gordonjcp (a) gjcp.net",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "Gordon JC Pearce",
    "subject": "[amsat-bb] Re: Decoding wideband recordings",
    "date": "2011-08-10T06:54:12Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/5HCWDGY7NTFKXMOTF2O7KEJMGKDL6VW4/",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "On Tue, 09 Aug 2011 15:54:15 -0700\nPhil Karn <[email protected]> wrote:\n\n> It's been suggested that I modify my ARISSat-1 BPSK-1000 telemetry\n> demodulator/decoder to accept wideband quadrature (I & Q) recordings\n> like those produced by most of the software defined radios out there.\n> \n> This is fundamentally not that hard, but first I need some information.\n> \n> How many people could actually use this? What is the format of the\n> recorded files? Is there a standard, or does each make of SDR produce\n> its own?\n\nAnyone with a Funcube Dongle, for a start.\n \n> If I could get a good sample wideband quadrature recording of the\n> ARISSat-1 downlink that includes the BPSK beacon, I could use it for\n> testing. Ideally there would be no need for any manual tuning because\n> the wideband recording would always contain the beacon regardless of\n> Doppler. All tuning would be in the demodulator software.\n\nIf you do get one, I'd like a copy as well.  The tuning bit is easy, you just multiply the incoming complex signal by a rotating vector.  Want to tune higher?  Spin that vector a little faster!\n\n> This might be a little compute-intensive so I can't guarantee that it'll\n> run in real time on older computers. I already make pretty heavy use of\n> the Intel SSE (vector arithmetic) instructions for FIR filtering and\n> Viterbi decoding. The SSE2 set introduced with the Pentium 4 has been\n> especially useful, so I would consider the P4 (or the AMD equivalent) a\n> minimum requirement. Of course, the newer and faster the CPU, the\n> better. I also make use of multiple CPU cores, particularly during the\n> acquisition phase, so the newer CPUs with lots of CPU cores would also\n> be preferred.\n\nI've successfully run lysdr on a 1400MHz Celeron M at 48kHz, although I had to back off the screen updates.  The FFT is actually quite fast, but screen updates with the Intel chipset tend to slow things down.  I considered using FFT convolution to replace the FIR filter, because the FIR is *really* slow.\n\nhttps://github.com/gordonjcp/lysdr\n\n\n\n-- \nGordon JC Pearce MM0YEQ <[email protected]>\n",
    "attachments": []
}