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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/O32OLOXTWPCONKF7VXMQ5OLYNRI7HG7B/",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/",
    "message_id": "[email protected]",
    "message_id_hash": "O32OLOXTWPCONKF7VXMQ5OLYNRI7HG7B",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/NHX6X5EKQIQSZSS634TXEOLCBVH3Q3HB/",
    "sender": {
        "address": "wb4gcs (a) amsat.org",
        "mailman_id": "87014499e012476c8198fad186f7f963",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/87014499e012476c8198fad186f7f963/emails/"
    },
    "sender_name": "Jim Sanford",
    "subject": "[eagle] Re: Eagle 10 MHz Clock",
    "date": "2007-04-12T01:03:04Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/24R5GB7B2KTHTVOBWEP42K4IZEJV5BBZ/",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "All:\nAll systems should be designed to fail gracefully upon loss of the 10MHz \nreference.  This was a key discussion in the UHF peer review.\nThis will be clarified when I get a chance to update the FRD, which is \nlow priority right now, compared to getting test results on U RX.\n73,\nJim\[email protected]\n\n\nRick Hambly (W2GPS) wrote:\n\n>Bill,\n>\n>s/c means SpaceCraft.\n>\n>It is a waste of time to design for operation without the 10 MHz satellite\n>oscillator (it is not a clock). The design will simply need to be redone. On\n>the other hand, if designs incorporate their own soft fail options, so much\n>the better.\n>\n>I expect a design for the 10MHz satellite reference based on a design Tom\n>and I have seen that includes its own soft fail redundancy. I will discuss\n>this possibility with Tom soon.\n>\n>Rick\n>W2GPS\n>AMSAT LM2232\n> \n>\n>-----Original Message-----\n>From: [email protected] [mailto:[email protected]] On Behalf Of\n>Bill Ress\n>Sent: Wednesday, April 11, 2007 1:17 PM\n>To: [email protected]\n>Cc: EAGLE\n>Subject: [eagle] Re: Eagle 10 MHz Clock\n>\n>Hi Tom,\n>\n>Thanks for your inputs.\n>\n>Do you have a time frame for your USO benefactor's commitment to the \n>program??\n>\n>We're designing based on 10 MHz reference assumptions and that leaves \n>me, at least,  with an empty feeling. Since over 10 subsystems will use \n>this reference, it would be great to get this block defined.\n>\n>As you know John has already designed for operating without the 10 MHz \n>satellite clock and I'm also doing the same.\n>\n>Oh - - - help with out Tom. You used \"s/c ranging\" in you one of your \n>recent posts. The \"s/c\" stands for what??? S and C transponders??\n>\n>Regards...Bill - N6GHz\n>\n>Tom Clark, K3IO wrote:\n>  \n>\n>>Bill Ress wrote:\n>>  \n>>    \n>>\n>>>(snip)\n>>>\n>>>If indeed the clock is used by all LO's it is important that the LO \n>>>designers know the reference's characteristics so that synthesis schemes \n>>>and loop bandwidths can be better defined.\n>>>  \n>>>    \n>>>      \n>>>\n>>Assume that it is a low noise crystal. Signals will come from an N-port\n>>driver that is a part of the USO. A good standard level will be 0 dBm\n>>into 50 ohms (although it could be a tad higher -- like up to 1V RMS =\n>>+13 dBm if really needed).\n>>\n>>I would suggest that each user system could use the precision reference\n>>if it is available, but should switch over to an internal oscillator if \n>>the precision source goes away. This is the way most counters, spectrum\n>>analyzers, etc work and it permits a good, simple \"fail soft\" option.\n>>  \n>>    \n>>\n>>>With that in mind, can you Tom, 1) determine what the specs of the \n>>>$ystem USO might be (or point me to a place when I might deduce them), \n>>>and 2) what's a realistic time frame for deciding if that $ugar \n>>>daddy/mommy comes through with a commitment? We not only have to get a \n>>>handle on the 10 MHz oscillator but the RF distribution circuitry after\n>>>      \n>>>\n>it.\n>  \n>\n>>>In regards to the RF distribution circuitry, I count 8 users of the 10 \n>>>Mhz clock. Help me out here if I missed one....\n>>>\n>>>1) V Transmitter\n>>>2) U Receiver (maybe two?)\n>>>3) L Receivers (two)\n>>>4) S Transmitter\n>>>5) S2 Receiver\n>>>6) C Transmitter\n>>>7) IHU\n>>>8) Spare (for X or K beacon or a \"contributing\" customer)\n>>>  \n>>>    \n>>>      \n>>>\n>>As Lyle mentioned, all the DSP widgets need the reference signal also.\n>>For precise ranging it is likely that some really tight special DSP code\n>>will be loaded into the DSP engines for maximum accuracy. This will be\n>>to ensure the flattest possible phase response thru the system (the\n>>group delay tau is measured as d(phase)/d(freq) over the however wide\n>>the passband can be).\n>>\n>>Thinking of obtaining the best possible accuracy, we may want to do U/V\n>>and a microwave pair simultaneously to provide a calibration of the\n>>ionosphere; the one-way group delay thru the ionosphere varies as 1/f²\n>>and has a magnitude ~2M at S-band.\n>>\n>>73, Tom\n>>\n>>\n>>\n>>  \n>>    \n>>\n>\n>_______________________________________________\n>Via the Eagle mailing list courtesy of AMSAT-NA\n>[email protected]\n>http://amsat.org/mailman/listinfo/eagle\n>\n>\n>_______________________________________________\n>Via the Eagle mailing list courtesy of AMSAT-NA\n>[email protected]\n>http://amsat.org/mailman/listinfo/eagle\n>\n>  \n>\n\n\n",
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