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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/O4CBHCQWIXPB6I76ZE7HLBOT23BUM32U/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "O4CBHCQWIXPB6I76ZE7HLBOT23BUM32U",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/O4CBHCQWIXPB6I76ZE7HLBOT23BUM32U/?format=api",
    "sender": {
        "address": "K3IO (a) verizon.net",
        "mailman_id": "79a9b3ddaa4b44baae47f92374974ac4",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/79a9b3ddaa4b44baae47f92374974ac4/emails/?format=api"
    },
    "sender_name": "Tom Clark, K3IO",
    "subject": "[amsat-bb]   Re: Galileo interference on L band",
    "date": "2006-09-22T03:51:40Z",
    "parent": null,
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/DBKWMB27RKVXRXAQJW5QPPJWRHHMIBUH/?format=api",
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/KB73KPLY2GJN3H4HFTY5STKQJEGXHB6N/?format=api"
    ],
    "votes": {
        "likes": 0,
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        "status": "neutral"
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    "content": "Sorry -- I've been away from home on business while the latest flack\noccurred under the general topic heading \"Galileo interference on L band\".\n\nFirst off, just so everyone can read the presentation materials that we\nused during the San Diego meeting, please take a look at the EaglePedia\nweb site at \nhttp://www.amsat.org/amsat-new/eagle/EaglePedia/index.php/San_Diego_Digital_Design_Meeting.\nThen take a look at my presentation \"Frequency Considerations for Eagle\"\nat\nhttp://www.amsat.org/amsat-new/eagle/EaglePedia/uploads/1/19/Microwave_Freq_x.pdf.\nYou will see (my slide 6) that I present the arguments pro/con about why\n(IMHO) L-band is at jeopardy as a long-term uplink band.\n\nLet me add a few comments about why I'm so concerned. The reason that\nthe Galileo E6 (functionally the same as GPS L2, and overlaying the\namateur 1260-70 MHz uplink allocation) is important for some uses is\nthat it, when used in combination with the primary 1.57± GHz \"L1\"\nfrequency (which is what all your cheap hand-held GPS receivers use),\ncan be used to correct the ionospheric errors; the ionosphere adds\nupwards of 10 meters to the pseudo-range for each GPS satellite. Because\nof geometric factors (expressed quantitatively in VDOP), this can in\nturn yield errors in height of up to about 30 meters. [The WAAS and\nEGNOS signals provide some correction for these biases to the few meter\nlevel, but cannot be relied on during severe ionospheric storms.]\n\nThere is a lot of factual evidence that when dual-frequency geodetic GPS\nreceivers (costing ~$25,000 -- hardly cheap!) have been used in\nproximity to terrestrial amateur L-band stations, the GPS performance is\nseriously degraded. I direct your attention to several reports on the topic:\n\n    * Must reading -- GPS/GLONASS vs L-band digipeaters (Also see GPS\n      World, Oct.2002) (warning contains numbers and equations, as well\n      as uncomplimentary comments about digipeaters)\n      http://elib.uni-stuttgart.de/opus/volltexte/1999/278/pdf/278.pdf#search=%22gps%20interference%20%20digipeater%22\n    * Amateur and Radar QRM reported at a 1999 technical meeting:\n      http://www.navcen.uscg.gov/cgsic/meetings/summaryrpts/33rdmeeting/Presentations/Weber.ppt\n    * A tutorial that shows how interfering signals can affect a spread\n      spectrum GPS rcvr (caution --  contains more\n      numbers): http://www.rin.org.uk/SITE/UPLOAD/DOCUMENT/Vuln-Owen.pdf#search=%22gps%20amateur%20interference%22\n\nEven though US amateurs may feel that Galileo is a \"European only\"\nproblem, read carefully Rick's (W2GPS) comments -- in his real life for\nmany years he was a VP with ARINC (the people who worry about standards\nin the airline industry) and was on many FAA and ICAO committees that\ndecide on airline safety.\n\nAlso realize that the Europeans are absolutely determined to develop\ntheir own GNSS (Global Navigation Satellite System) call Galileo -- in\npart because they don't really trust a system that depends on the US\nMilitary, and in part because they see a giga-Euro business opportunity\nfor the EC. Who knows how long it will survive, but the Russians have\ntheir competing GLONASS system. And both the Chinese and Japanese see\nthat they need to enter into the GNSS race is they are to be world-class\ntechnical competitors.\n\nWe, the Eagle technical team, have never said that L-band won't work NOW\nor 5 years from now. But our vision for Eagle is that when the first one\nflies 4-5 years from now, we want it to be a useful resource for at \nleast a 10 year lifetime. We are very concerned about making a several\nmillion dollar (after you count the volunteer builder's blood, sweat &\ntears) investment only to have it blown away right after launch by the\nGNSS cartels just because we picked L-band to be anything like a\n\"primary\" uplink.\n\n73, Tom\n\n\n",
    "attachments": []
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