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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/N5YC364R6UXUYKNMABOXZLABDX6HZQ2Q/",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/",
    "message_id": "[email protected]",
    "message_id_hash": "N5YC364R6UXUYKNMABOXZLABDX6HZQ2Q",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/MFJ5ISUGIIF4X2OAPFY2GHL7ABI764MO/",
    "sender": {
        "address": "bob (a) evoria.net",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "Bob Stewart",
    "subject": "[amsat-bb] Re: FM sat frequencies?",
    "date": "2007-09-10T18:40:37Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/MFJ5ISUGIIF4X2OAPFY2GHL7ABI764MO/",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "John,\nIt's pretty clear from tracking the doppler effect during\nmultiple passes that these frequencies are not correct.\nI believe I read somewhere that AO-27 was being quoted\nat 436.797, which is pretty much what my measurements\nshowed.  Of course, my measurements are going to be\noff by however much my old FT-726R is wrong.  But I\nhave reason to believe that's less than 1kHz.\n\nHere's how I'm coming up with my figures:  In the gpredict\nprogram, there is an area where the doppler shift is\ncalculated.  As posted recently, I hacked this to show\nthe actual frequency that should be on my dial.  I added\nthe following line just after the doppler was calculated.\nI also added an if statement to select a specific satellite,\nbut that is irrelevant to this discussion.\n\ndoppler=doppler*4.367950/100.0+7950.0;\n\nIn the program, the doppler is calculated in hz for a 100mHz \nsignal.  My idea was to simply rescale that to 436.7950 by \nmultiplying by 4.367950.  I need to move the decimal point\nover two more so that I can display the 100kHz and down\nfrequency readout, so I divided by 100.\n\nThe problem was that the results were wrong by different\namounts for the three satellites.  The only way to get\nthe right figure was to start moving the satellite's implied\nfrequency.  e.g.:\n\ndoppler=doppler*4.367920/100.0+7920.0;\n\nThe result from this calculation tracks SO-50 pretty well, so\nunless my idea is fundamentally wrong, I believe that SO-50\nis transmitting near 436.7920.\n\nBob\n\n\n\n--- John Kopala <[email protected]> wrote:\n\n> The frequencies given for each of the easy satellites are:\n> \n> AO-27    436.795\n> SO-50    436.795\n> AO-51    435.300\n> \n> AMSAT gives the details for the individual satellites and their uplink and \n> downlink frequencies.  Go to the following site and then simply click on the \n> satellite you are interested in. \n> http://www.amsat.org/amsat-new/satellites/status.php\n> \n> With doppler shifts as the satellites make a pass the actual receive \n> frequency could vary by as much as about 10 KHz plus or minus the nominal \n> frequency.  The only time you would ever receive the satellite exactly on \n> its downlink frequency would be when the satellite heading is exactly 90 \n> degrees from your bearing to the satellite.  At that point the satellite is \n> tangential to a circle whose center is your location and is neither moving \n> toward or away from your location.\n> \n> I am using an IC-910H.  For manual tuning at the beginning of a pass, I \n> simply tune about 5 to 9 KHz higher (depending on the elevation of the pass) \n> than the nominal frequency.  With the AFC turned on, the radio will \n> automtically lock into the signal when it becomes strong enough and track \n> the frequency as the doppler shift changes the receiving frequency during \n> the pass.  At loss of signal, the receive frequency will be below the \n> nominal frequency by about the same amount it was above at the start.\n> \n> John Kopala\n> N7JK\n> \n> > Date: Sun, 9 Sep 2007 19:44:15 -0700 (PDT)\n> > From: Bob Stewart <[email protected]>\n> > Subject: [amsat-bb]  FM sat frequencies?\n> > To: Amsat-BB <[email protected]>\n> > Message-ID: <[email protected]>\n> > Content-Type: text/plain; charset=iso-8859-1\n> >\n> > Does anyone know the actual downlink frequencies of the\n> > easy sats?  From messing around with my hack for gpredict,\n> > I get the values below, but it would be nice to know the\n> > correct values as a check against what I'm doing.\n> >\n> > AO-27     436.7972\n> > SO-50     436.7920\n> > AO-51     435.3008\n> >\n> > Bob - AE6RV\n> \n> \n> _______________________________________________\n> Sent via [email protected]. Opinions expressed are those of the author.\n> Not an AMSAT-NA member? Join now to support the amateur satellite program!\n> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb\n> \n\n\n",
    "attachments": []
}