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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/IBXAPAPK6UVDLGFQRVYQLPJDJDAJ6LR7/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "IBXAPAPK6UVDLGFQRVYQLPJDJDAJ6LR7",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/4RX4BW32DKBSIEE576L27EOPNPJSQR6U/?format=api",
    "sender": {
        "address": "ve9qrp (a) gmail.com",
        "mailman_id": "4d6061838db34aba9a1c4722addebfaf",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/4d6061838db34aba9a1c4722addebfaf/emails/?format=api"
    },
    "sender_name": "Bruce Robertson",
    "subject": "[amsat-bb] Re: Icom 910H vs Kenwood TS2000",
    "date": "2009-12-01T00:11:59Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/4RX4BW32DKBSIEE576L27EOPNPJSQR6U/?format=api",
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/PISA2BUT6IZQFMEE3PZ6XEKOH3Z4P3MP/?format=api"
    ],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "On Mon, Nov 30, 2009 at 6:35 PM, Tom <[email protected]> wrote:\n>\n> Being a recent newbie to the LEOs it had never even occurred to me that too\n> narrow a beam width could present a problem with staying pointed at those\n> satellites. Thanks, Reid, for bringing that thought up in my mind. I wasn't\n> taking it out of context. I was just wondering if it was an unforeseen\n> problem (by me) that I needed to address. It's things like this that allow\n> us to learn.\n>\n> It appears that a narrow beam width is not normally a problem and I thank\n> John and others who pointed that out.\n>\n\nI'm going to elaborate on this discussion, for the benefit of\nbeginners who are considering building new stations with tracking\nantennas. The narrower the beam, of course, the greater the gain when\npointing at the bird, both transmit and receive, and -- this is the\ncritical issue -- the lower the gain when you are pointed away from\nthe bird. Now with LEO satellites, some of which cross the sky in say\n15 minutes, you need to have everything spot-on if your beamwidth is\nvery narrow: the station clock has to be accurate within a second, the\nkeps have to be up-to-date, etc. otherwise, your computer is telling\nthe rotors to point in the sky where the satellite is going to be in\nfive seconds, or will be in five. Especially with high passes, you can\nbe off by enough to not be able to hear the bird at all. So on\nreceive, long antennas, besides the additional expense and challenge\nof mounting them, also add the challenge of getting your station\nperfectly aligned, or you'll hear zippo.\n\nOn transmit, long antennas present another challenge: they\n'concentrate' your signal so that it might well be excessively\npowerful for the satellite in question. If my homebrew 7 - element\n70cm yagi often needs to be down around 5w xmit on VO-52 to be in the\nright range of effective power, how will I deal with things when I\nhave a 40-element beam? By all rights, I should put an attenuator\nbetween the rig and the antenna so that I can get down under a watt!\nIt is my opinion, in fact, that a significant proportion of the\nover-powered signals on our birds are from people in just this\nsituation: people using HEO antenna systems that simply can't provide\na small enough signal!\n\nIn fact, LEO satellites do not require these sorts of antenna systems\nfor reliable use. A beginner will be perfectly happy with, say, four\nelements on 2m and 6-7 on 70cm (assuming the use of low-noise preamps,\nwhich you are *crazy*to do without on long antennas, too). The beauty\nof this system is that if a high wind knocks it slightly out of whack\nin azimuth, it will not be the end of your satellite work: you'll just\nhave weaker signals, not silence. The other beauty of this system is\nthat it doesn't require an elevation rotor *at all*. Because the\nelevation pattern of the antennas will more-or-less fill the sky if\nyou point the array up about 10-20 degrees (make it 10 if you have a\nclear horizon). Now, suddenly, you've avoided all the hassle of\nanother rotor, you've made your array lighter and easier to work with,\nand you have way less of a demand on your pointing system. Heck, if\nyou want to go ol' school, you can do the pointing yourself with a\ntwist of the dial.\n\nThese yagis do not need to be brilliantly built: mine were made with\nwelding rod and pine wood. They had very strange lobes off the side,\nand all the rest, but they netted me lots of Q's and were very\nreliable.\n\nTo be even more radical, I urge beginners to start with\nomni-directional antennas and low-noise preamps. A wire dipole or a\nvertical, both with almost no coax between them and the preamp, should\nhear 'stuff' really well. Not Q-5, but a start. Then use this as a\nbaseline from which to compare the theoretical and real-world\nimprovement you get with your yagi array. If you aren't getting\nimprovement, then work out what's up.\n\nThis is not an argument against long arrays. I'm building some that I\nbought from someone on this list around this time last year. I want to\ndo some exotic stuff like work Russia over the pole on AO-07 or hear\nevery last beep out of the newest cubesat. But I'm aware that in my\nwindy region these are going to be a bear to keep in place. So I'm\nputting as much work into an omni array, too. I plan to transmit from\nthe latter when things get too QRO.\n\nI guess in summary I'd say that in my opinion a big antenna array\nisn't like a high-power computer, which works the same as a\nlower-powered one, but has the umph when you need it; it is like\nbuying a high-powered plane as a new pilot: significantly more\nchallenging, and possibly leading to frustration.\n\n73, Bruce\nVE9QRP\n\n>\n>> I have used a Cushcraft 13B2 (13 elements) on 2m and a Cushcraft 719B (19\n> elements) on 70cm on the\n>> satellites with no problem.  Didn't experience either as being too narrow\n> beamwidth for sat use.\n>>\n>> 73s John AA5JG\n>>\n>> I am amazed at how many people take things stated out of context on this\n>> reflector. I never said that any of the arrays would not work due to\n>> problem they were having hearing the satellites and it was stated that\n>> if none of the other suggestions worked to consider that the arrays they\n>> are using are pointed correctly in the correct direction of the\n>> satellite. Pointing being off, the nulls could easily block the\n>> satellite's reception. The larger the array the more this might be\n>> evident. The larger the array, stacked arrays and even dish antennas,\n>> pointing becomes a bit more critical.\n>>\n>> Reid, W4UPD\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-- \nhttp://ve9qrp.blogspot.com\n\n",
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