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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/KGXJVGCYH2VYJINMZUUBORH3PURYGJRX/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "KGXJVGCYH2VYJINMZUUBORH3PURYGJRX",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/V5WDPF4VXTYGDUDOYX2LQ5FBM5AK6ONM/?format=api",
    "sender": {
        "address": "kene (a) braxtontech.com",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "Ken Ernandes",
    "subject": "[amsat-bb] Re: SDX transponder timing delay measurements?",
    "date": "2006-09-12T14:15:34Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/HEHG25AAHYUG3LVMFBFFFNPSRIYPY5ZZ/?format=api",
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/BEW5EQ4VHUUXS2UGZBI2CBRBVZT2M4Z2/?format=api",
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/TKQSHWHX4J55QOWBRYTPTWSV65UAN6E7/?format=api"
    ],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Just to clarify what Bob said, an extra 35ms delay will not be a big issue\nto the operators.  But as he also indicated, 35 ms is very \"noticeable\" when\nmaking Range measurements -- consider the speed of light (300,000 km/sec) *\n0.035 sec = 10,500-km.  Hence his statement that the actual number will be\nimportant for ranging.\n\n>From a Guidance & Navigation point of view there are two things that are\nimportant to consider here:\n\n1.  If the timing delay on Range measurements is accurately estimated (or\nbetter yet measured), it can be calibrated out for the purposes of Orbit\nDetermination (OD).  My OD software has a Transponder Range Bias as an input\nparameter and has the ability to fine-tune the estimate of that Bias as part\nof the correction process.  The fine-tuning works well given a good initial\nestimate -- best done by making measurements with the flight\nhardware/software.\n\n2.  What is also very important is how *consistent* is the delay.  If it's a\nrock-solid 35 milli-sec (i.e., rock solid = a very small variation), that's\nbetter than an average value of 35 micro-sec with say a +/-5 milli-sec\n(i.e., 1500-km) uncertainty.  The OD process can easily calibrate out a\nconstant offset (bias).  But the greater the uncertainty (variability) to\nthat bias, the greater will be uncertainty in the OD results (and thus\npoorer quality orbital parameters).  Therefore, if tradeoffs can be made in\nthe design, a bigger delay that's nearly constant is *far* preferable than a\nsmaller average delay with even a modest amount of variance.\n\nAs a design goal, it would be helpful to the OD process if the delay could\nbe made consistent within about +/-5 micro-sec -- i.e., 1500 meters (smaller\nis better).  It is also important to quantify the standard deviation to that\nbias is since that is also factored into the OD process.\n\n73, Ken Ernandes, N2WWD\n\n\n\n\n\n\n-----Original Message-----\nFrom: [email protected] [mailto:[email protected]]On\nBehalf Of Robert McGwier\nSent: Tuesday, September 12, 2006 8:39 AM\nTo: Steve Meuse\nCc: [email protected]\nSubject: [amsat-bb] Re: SDX transponder timing delay measurements?\n\n\nI think it is about 35ms.  It is not noticeable and especially with the\nround trip time thrown in the mix,  it will definitely not be\nnoticeable.   The number will be important to us when we want to do ranging.\n\nBob\n\n\n\nSteve Meuse wrote:\n> Douglas Quagliana expunged ([email protected]):\n>\n>\n>> I know the design isn't even done yet, but has anyone\n>> ever measured the time delay of an RF signal *through*\n>> the (demo) version of SDX?\n>>\n>\n> There was a demo of the board at Dayton, I was lucky enough to get a demo\nwhile we were setting the booth up. The demo setup, if I remember correctly,\nwas using two SDR-1000's. I didn't find the delay noticable at all.\nPropagation delay is much more of an issue for HEO.\n>\n> BTW, the SDX sounded FANTASTIC! I had goosbumps when N4HY tuned to the\nbeacon :)\n>\n> -Steve\n> N1JFU\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\n--\nAMSAT VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats,\nNJQRP/AMQRP, QRP ARCI, QCWA, FRC. ARRL SDR Wrk Grp Chairman\n\"You see, wire telegraph is a kind of a very, very long cat.\nYou pull his tail in New York and his head is meowing in Los\nAngeles. Do you understand this? And radio operates exactly\nthe same way: you send signals here, they receive them there.\nThe only difference is that there is no cat.\" - Einstein\n\n_______________________________________________\nSent via [email protected]. Opinions expressed are those of the author.\nNot an AMSAT-NA member? Join now to support the amateur satellite program!\nSubscription settings: http://amsat.org/mailman/listinfo/amsat-bb\n\n",
    "attachments": []
}