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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/WGRPCSBDKBDHF3PQEBBJQGFJQDDGSWDB/",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/",
    "message_id": "FACC3FD524D1435E9914607D68D71CE6@CSI9020",
    "message_id_hash": "WGRPCSBDKBDHF3PQEBBJQGFJQDDGSWDB",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/HXAX3GIG5EQJECYZPH4OMTXXYAD7HC7L/",
    "sender": {
        "address": "scott23192 (a) gmail.com",
        "mailman_id": "120e10e05ba14969a11da0a96d21e355",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/120e10e05ba14969a11da0a96d21e355/emails/"
    },
    "sender_name": "Scott",
    "subject": "Re: [amsat-bb] Note ref. doppler w/ UHF iGate listener for ISSPacket",
    "date": "2016-11-14T15:35:16Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/CJVLCBCTPHCWGVSMQREFCMUEATIGSAPK/",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Great tips, Dani - thanks for the input!\n\nI tried the code from https://github.com/cubehub/doppler but ran into \ndifficulty with the dependencies installing correctly.  But I really should \nrevisit that since it is the best solution.\n\nI had NOT, however, considered the possibility of multiple APRS-capable \nsatellites on UHF being visible at the same time.  That is ugly, but as you \nmentioned we only have the ISS to accommodate for now on 70cm.\n\nGood info!\n\n-Scott,  K4KDR\n\n\n=================================================================\n\n-----Original Message----- \nFrom: Dani EA4GPZ\nSent: Monday, November 14, 2016 10:26 AM\nTo: [email protected]\nSubject: Re: [amsat-bb] Note ref. doppler w/ UHF iGate listener for \nISSPacket\n\nEl 13/11/16 a las 20:48, Scott escribió:\n\n> But another issue that several folks have pointed out is that with the \n> more\n> substantial doppler shift at 70cm, a receiver set to a single frequency\n> will miss much of the traffic sent back down from the ISS.\n>\n> [...]\n>\n> It crossed my mind that, at the point of closest approach, the doppler\n> frequency is changing quite rapidly.  So, I thought that I might improve \n> my\n> count of iGated packets if I listened on a frequency that would be viable\n> for a longer period of time.  Using (WD9EWK) Patrick's doppler adjustment\n> guide as a reference, I chose to change my listener to 437.555.\n\nHi Scott and all,\n\nAnother thing that you can do is to correct for Doppler in software\n(obvious).\n\nIf you're using an FM radio, this may me more complicated because you\nneed to set up CAT, but if you're using an SDR, it's just a matter of\nusing the appropriate software.\n\nSince you're asking this specifically for iGates, we can assume that you\nhave an internet connection on your receiver to fetch TLEs automatically.\n\nThen you can use whatever Doppler correction tool you like to be in tune\nduring all the ISS pass. For instance, this command line tool:\n\nhttps://github.com/cubehub/doppler\n\nshould be useful, especially for embedded systems such as a Raspberry Pi.\n\nThe disadvantage of doing Doppler correction is that you can only do it\nfor one satellite. In 145.825 there is the problem that there are\nseveral satellites you want to receive, several of them may be in view\nsimultaneously, and they will have different Doppler offsets. Still, you\ncould setup the system so that if there's only one satellite in view you\ncorrect for that satellite and if there are several you either\nprioritize and correct for one of them, take an average of the\ncorrections, or just do no correction. This is more complicated, of course.\n\nHowever, on 437.550 you only have the ISS, so it makes much sense to\ntrack Doppler correction only for the ISS, and this is much easier than\nhandling several satellites.\n\nSo, nothing new here. What I mean is that automatical Doppler correction\nfor the ISS using an RasberryPi and RTL-SDR is not that hard (and much\nbetter solution than listening on a fixed frequency). Come on guys, we\ncan do it!\n\n\n73,\n\nDani EA4GPZ. \n\n",
    "attachments": []
}