Email Detail

HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/NJYZ2AROB5AHLHNE32KNDD6L6ETYPUXE/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "NJYZ2AROB5AHLHNE32KNDD6L6ETYPUXE",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/JXR4XNGAJYG4R5ESUJPIDU6GMULODX2L/?format=api",
    "sender": {
        "address": "on4hf (a) telenet.be",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "Eric Knaps, ON4HF",
    "subject": "[amsat-bb] Re: Doppler Correction?",
    "date": "2011-07-25T16:30:34Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/JXR4XNGAJYG4R5ESUJPIDU6GMULODX2L/?format=api",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Hello John,\nI totaly agree with you. I work with full doppler control (rx and tx) \nfrom the moment that I started on the birds.\nThat way I can concentrate more on seeking new stations and logging them.\n\n73,Eric.\n\nAmateur Radio Station ON4HF\nEric Knaps\nSatellite manager UBA\n\nTel. +32472985876 (mobile)\n\nhttp://www.on4hf.be\n\n\nOp 25/07/2011 4:00, John Papay schreef:\n> The purpose of full doppler correction is to keep your signal in\n> the exact same spot on the receiver in the satellite.  It has a finite\n> passband and if you don't correct your uplink, you move within that finite\n> passband.  Theoretically a single linear transponder can support many\n> conversations but it will not support the maximum unless everyone stays\n> put at the satellite receiver.  Those who don't doppler correct slide\n> within the\n> passband and run into those who are staying put.  Of course if you adjust\n> your uplink so you stay put at the satellite, you have to adjust your\n> receiver to hear yourself because of the doppler shift in the other direction.\n> Both uplink and downlink require doppler correction in this case.\n>\n> If you don't have a rig that can be computer controlled or if you are\n> operating portable and can't readily incorporate a laptop into your\n> setup for whatever reason, then by all means manually adjust the highest\n> frequency since that is the one that changes three times faster than the\n> lower frequency in a v/u satellite.  You simply do the best you can.\n>\n> However, if you have a home rig that can be computer controlled, then by all\n> means use a computer to adjust your doppler.  Stay in one spot in the\n> satellite's passband.  You can make faster contacts since you only have\n> to pick up the mic to talk or use the key to send cw.  If you are working\n> dx and the window is short, being on frequency and staying put will help\n> put that distant grid in the log.\n>\n> The program does all the work but you must be sure that your keps\n> are current AND your computer clock is accurate to the second.  On a\n> high pass when the satellite is overhead, the doppler changes very fast\n> and even a few seconds of clock inaccuracy will have you not hearing\n> yourself in a normal voice.  At lower elevations the doppler is not as\n> severe so a few seconds won't make much difference.\n>\n> Use the HO-68 beacon to test your doppler correction.  Set your radio for\n> CW with a 500 Hz or better bandwidth.  Pick a high pass where the bird will\n> get up over 45 degrees.  Tune the beacon in at your AOS and then don't touch\n> the dial.  If the CW note stays constant over the entire pass, your system\n> is operating perfectly.  Make sure your program settings are such that there\n> are frequent frequency updates.  I have mine set at 1 second no matter what.\n> Some older radios will not accept frequency changes while you are\n> transmitting.  In\n> that case, make sure you only key down for short periods of time so the\n> radio frequency can be updated.\n>\n> Of course you must adjust your uplink calibration on SatPC32 so that you\n> hear yourself on the downlink.  Hearing yourself in a normal voice will\n> be an indication that you have your calibration set properly.\n>\n> Most of the birds stay on frequency, but I've noticed that AO-7 Mode B will\n> be off by 1700Hz when it changes from Mode A to Mode B.  Normally we would\n> not observe this phenomenon but since lately we have had this mode change while\n> over North America we are able to experience it.  Within a few minutes, the\n> satellite is down to a 1200 Hz offset.  I'm not sure what happens on the next\n> pass because it is out of my footprint.  The next morning, however, the bird\n> is back to my normal setting.  This means the frequency drifts about 1700 Hz\n> back down to it's steady state value.  The other birds may have some slight\n> drifting, probably due to spacecraft temperature but it is minimal, less than\n> a few hundred Hz.  So when you are trying to make a contact on the first\n> AO-7 pass in Mode B, be prepared to readjust your uplink calibration so you can\n> hear yourself.  It may be as much as 1700Hz at the start.\n>\n> In my opinion, everyone that can control their radio for doppler should do so.\n> Doppler correction gives us the maximum usage out of our linear transponders.\n> Why go through the agony of fiddling with your radio when your computer can\n> make your life so much easier.  You will never have to apologize for not being\n> on frequency.  If I wasn't able to have doppler control on my radio, I wouldn't\n> spend much time on the linear birds, unless of course there was a rare grid\n> to be worked.<grin>\n>\n> 73,\n> John K8YSE\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",
    "attachments": []
}