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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/HXC2JOJDEIOEA6XXHGNYJCJK54VZPIFN/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "004201c868db$fdd9b910$6401a8c0@Sony2G4",
    "message_id_hash": "HXC2JOJDEIOEA6XXHGNYJCJK54VZPIFN",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/FVVMU6KDIBRYIBRJKDVHIPGOYYDN3T5M/?format=api",
    "sender": {
        "address": "n5gui (a) cox.net",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "James Whitfield",
    "subject": "[amsat-bb] Re: Automatic doppler tracking of DSB",
    "date": "2008-02-06T16:19:04Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/ZWYLYBSJEEYMMU7TG7733MLEM2M7LCSE/?format=api",
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/CFEJG7NHLSOAEHEKLBU4KYWCEKKVCEPI/?format=api"
    ],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "---------- From: \"Jim Towler\"\n>In general terms, this is largely true, and for a 2m uplink, little\n>or no tuning is required on AO-51/Echo etc. However, a\n>number of earlier emails spoke of the more critical need for\n>AO-16 as it appears to have tight filters compared to a typical\n>FM uplink. Careful control of Doppler for the uplink would\n>allow a more full use of the entire filter bandwidth, rather than\n>using FM-Narrow, and having weak audio.\n\nHmmmmm. I would like to claim that I am a victim of the news article about\nthe test mode for AO-16 on the ARRL website, but that would be admitting\nthat I am gullable enough to believe the FM uplink did not need Doppler\nshift compensation.  That it works at all on a system that was intended to\nbe digital is a blessing.\n\n>I still like the idea of attempting CTCSS....\n\nI think it is a great idea.  I can imagine a comparison of three modes using\nit.  The first is to use CTCSS in the uplink to model what was previously\ntried with SSB and pilot carrier.  That is of course on the assumption that\nthe pilot carrier did not need to be zero beat with the SSB signal.  If you\ncan find out about their experiements you might find suggested frequency and\npower levels to use.\n\nThe second mode would be to use the Costas Loop to compensate for Doppler\nshift and synchronously detect the DSB signal.  That would give you\ncomparison of the effectiveness of the Doppler tracking and maybe compare\nthe noise benefit of the synchronous detector.\n\nThe third mode would be Costas Loop without CTCSS to find out if it really\nhelps, and how much.  As I indicated previously, I am guessing that the\nsystem will acquire lock on voice power peaks, so it may not require much\nCTCSS power to maintain the system lock.  It may well be that the power\nrequired to maintain lock depends on the rate of change in the Doppler\nshift.  Said another way, it may require more power to hold the signal at\nthe time of closest approach than when the Bird is near the horizon, comming\nor going.\n\n>Not related to AO-16, but something I intended to test on FO-29\n>at some point, was \"two-station Doppler correction\"....\n\nIt is an interesting set of control systems, one for transmit and an\nindependent one for receive.  The transmit system would seem to be open loop\nand based on the known position of the other station and path of the Bird.\nThe receive system could be either open or closed loop, perhaps both with\nthe ability for the operator to select the \"better\" channel.   It might also\nbe possible to feed the receive side closed loop parameters into the\ntransmit system.  I will have to think a little more, but there does not\nseem to be any way to close the transmit loop.\n\n\nBest Wishes\n\nJames\n n5gui\n\n\n",
    "attachments": []
}