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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/6OU5MQREKOOQBZBL3HQKT3X4UUSIRDJ6/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "6OU5MQREKOOQBZBL3HQKT3X4UUSIRDJ6",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/UPK4RTUGRHTRVDPDYXKITZDIFRCLMXOK/?format=api",
    "sender": {
        "address": "bill (a) hsmicrowave.com",
        "mailman_id": "d7ecbf0c1df148f289f27dd7a8c37974",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/d7ecbf0c1df148f289f27dd7a8c37974/emails/?format=api"
    },
    "sender_name": "Bill Ress",
    "subject": "[amsat-bb] Re: Galileo interference on L band",
    "date": "2006-09-21T18:48:55Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/QORV7YMUED3SXML2LANNOFELBCCTAV2S/?format=api",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Hi Bob,\n\nWhile I do concur that Galileo interference is a \"potential but currently\nunknown\" problem, I'm approaching the issue with confidence that their\ndesign teams will find ways to handle the potential interference issues they\nappear to be well aware of.\n\nJust look at their report \"Galileo Interference Measurement Campaign\" at:\nhttp://www.joanneum.at/index.php?id=530&L=1\nand you will read about the many sources of potential interference they will\nneed to be concerned about. In all their travels they found only one source\nof Amateur interference: an Amateur TV repeater. (I guess AO-51 wasn't in\nthe L/S or L/U mode at the time of their trip!)\n\nNot only must the Galileo system be designed to handle terrestrial\ninterference but now that the GPS and Galileo frequencies have overlap they\nmust handle mutual interference. I can reference reports on that issue too.\n\nThen too - the Galileo E6 signal (pilot carrier at 1276 Mhz) has a\nsignificant null region around 1260+ Mhz. Now that's the lower end of our\nAmateur satellite band. P3E has L2 located there (good choice guys and\ngals!) and I would trust that is where you plan on locating Eagle's L-Band\nreceiver.\n\nBy the way, the upper null falls around 1296 MHz so EME activities may also\nbe able to co-exist.\n\nThis isn't the first time Amateurs had to deal with interference sources and\nsurely won't be the last (i.e. power line internet), but we can't just admit\ndefeat so early in the game - vacant our use of L-Band - and make the job of\nregulators who might wish to take the allocation away from us any easier\nthan necessary.\n\nAgain, I think we can co-exist - my positive outlook. Naturally we must stay\nin touch with their progress and I would further suggest we establish a\ndialog with them early on to indicate to them we are aware of the potential\nfor interference we could cause and try to \"work with them\" to find areas of\nmitigation.\n\nAdmittedly a tall task but surely its worthy of an attempt. In other words -\ntry to get on their good side early in the game and let's take a pro-active\napproach to this potential problem!\n\nRegards...Bill - N6GHz\n\n-----Original Message-----\nFrom: [email protected] [mailto:[email protected]]On\nBehalf Of Bob McGwier\nSent: Thursday, September 21, 2006 9:16 AM\nTo: John B. Stephensen\nCc: [email protected]\nSubject: [amsat-bb] Re: Galileo interference on L band\n\n\nAllow me  to add (AGAIN) for emphasis that the issue is the near/far\nproblem.  Maybe I should explain this in more detail as I think John and\nI are assuming that while you might not necessarily be able to calculate\nthe exact path loss,  you had an intutive understanding for the\nproblem.  The differences in distances are ENORMOUS.  The Galileo\nsatellites will typically be something like the circumference of the\nearth away from you and the best case is 1/2 the circumference of the earth.\n\nThe path loss from Galileo to your location is in the very best case\ngiven the planned orbit is approximately 180 dB.\n\nThe path loss from you to your neighbor a km away is about 93 dB.\n100km improves this by approximately 55  dB.  That is,   ANY\ninterference from your station given equal powers is inherently 87 dB\nstronger at the ground station than Galileo at 1 km  and at 100 km, it\nis inherently ~30 dB stronger.   Even if you factor in different powers\non the spacecraft and ground,  and losses from circularity,\npolarization,  sidelobes,  blah blah,   10^9  is a BILLION times\nadvantage for your signal to clobber the Galileo signal before you take\nthese into account.  This calculation does not include any shaping of\nthe beam on your part so a few dB gain in the direction of the ground\nstation and the problem is worse.     As the airplane approaches your\nlocation from 100 km,  you will overload the front end without drastic\nmeasures taken by the manufacturers.\n\nPlease understand the engineers designing the Galileo system understand\nthese issues well.  They will argue very strongly that the interference\nsources be removed since they do not wish to notch you by 90 dB!\n\nBob\nN4HY\n\nJohn B. Stephensen wrote:\n\n>The article predicts that there may be limitations on the amateur service.\n>The biggest problem is sidelobes from the antenna that can be of either\n>polarization sense. A 16 kW EIRP uplink can easily generate 500 W EIRP\n>sidelobes (15 dB down) within the Galileo receiver passband and,\nreplicating\n>the calculations outlined in the article, they can cause interference from\n>42 km away.\n>\n>73,\n>\n>John\n>KD6OZH\n>\n>----- Original Message -----\n>From: \"Marc Franco\" <[email protected]>\n>To: <[email protected]>\n>Sent: Wednesday, September 20, 2006 19:03 UTC\n>Subject: [amsat-bb] Galileo interference on L band\n>\n>\n>\n>\n>>John,\n>>\n>>Galileo is circularly polarized, so using the opposite\n>>polarization sense will help.\n>>\n>>An excellent paper on Galileo interference was written\n>>by Peter Blair, G3LTF, a well known moonbounce\n>>authority and outstanding engineer. The paper can be\n>>found following this link:\n>>\n>>http://www.southgatearc.org/articles/galileo.htm\n>>\n>>\n>>73, Marc N2UO\n>>\n>>\n>>--- \"John B. Stephensen\" <[email protected]> wrote:\n>>\n>>\n>>\n>>>Unfortunately, the Gaileo downlink covers 1258-1299\n>>>MHz, the first satellite\n>>>has been lanched and the satellites in the\n>>>constellation will be on over the\n>>>entire world. Our uplink antennas have sidelobes\n>>>that are 10-20 dB down, so\n>>>a 1 kW EIRP SSB uplink results in 10-100 W radiated\n>>>towards terrestrial\n>>>receivers. A 256 kbps uplink would require 16 kW\n>>>EIRP and be 0.5-1 MHz wide.\n>>>\n>>>P3E has a second L receiver tuned to a null in the\n>>>Galileo signal (there is\n>>>only one null in the 1260-1270 MHz band) but no one\n>>>knows if this will help.\n>>>SSB users can move to the U uplink if L is a\n>>>problem. However, this only\n>>>works for narrowband signals. A wideband uplink\n>>>won't fit in the null and\n>>>can't move down in frequency.\n>>>\n>>>73,\n>>>\n>>>John\n>>>KD6OZH\n>>>\n>>>\n>>__________________________________________________\n>>Do You Yahoo!?\n>>Tired of spam?  Yahoo! Mail has the best spam protection around\n>>http://mail.yahoo.com\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>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\n--\nRobert W. McGwier, Ph.D.\nCenter for Communications Research\n805 Bunn Drive\nPrinceton, NJ 08540\n(609)-924-4600\n(sig required by employer)\n\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",
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