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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/PISA2BUT6IZQFMEE3PZ6XEKOH3Z4P3MP/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "PISA2BUT6IZQFMEE3PZ6XEKOH3Z4P3MP",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/4RX4BW32DKBSIEE576L27EOPNPJSQR6U/?format=api",
    "sender": {
        "address": "mat_62 (a) netcommander.com",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "Michael Tondee",
    "subject": "[amsat-bb] Re: Icom 910H vs Kenwood TS2000",
    "date": "2009-12-01T00:43:54Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/IBXAPAPK6UVDLGFQRVYQLPJDJDAJ6LR7/?format=api",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "All excellent points Bruce and I might add to any beginners out there, \nthe reason I went the way I did  with my antennas back when I had my \nfull blown satellite rig is that I \"wanted\" the challenge of building a \nhomebrew AZ/EL setup. I did enough research to know that it certainly \nwasn't necessary for LEO's, omni's are fine. I'm considering homebrewing \nsome eggbeaters, groundplanes and turnstiles just to experiment with. I \nguess I got it from my late father ( the original W4HIJ), I like to play \nwith antennas. :-)\nMichael\nBruce Robertson wrote\n>> I'm going to elaborate on this discussion, for the benefit of\n>> beginners who are considering building new stations with tracking\n>> antennas. The narrower the beam, of course, the greater the gain when\n>> pointing at the bird, both transmit and receive, and -- this is the\n>> critical issue -- the lower the gain when you are pointed away from\n>> the bird. Now with LEO satellites, some of which cross the sky in say\n>> 15 minutes, you need to have everything spot-on if your beamwidth is\n>> very narrow: the station clock has to be accurate within a second, the\n>> keps have to be up-to-date, etc. otherwise, your computer is telling\n>> the rotors to point in the sky where the satellite is going to be in\n>> five seconds, or will be in five. Especially with high passes, you can\n>> be off by enough to not be able to hear the bird at all. So on\n>> receive, long antennas, besides the additional expense and challenge\n>> of mounting them, also add the challenge of getting your station\n>> perfectly aligned, or you'll hear zippo.\n>>\n>> On transmit, long antennas present another challenge: they\n>> 'concentrate' your signal so that it might well be excessively\n>> powerful for the satellite in question. If my homebrew 7 - element\n>> 70cm yagi often needs to be down around 5w xmit on VO-52 to be in the\n>> right range of effective power, how will I deal with things when I\n>> have a 40-element beam? By all rights, I should put an attenuator\n>> between the rig and the antenna so that I can get down under a watt!\n>> It is my opinion, in fact, that a significant proportion of the\n>> over-powered signals on our birds are from people in just this\n>> situation: people using HEO antenna systems that simply can't provide\n>> a small enough signal!\n>>\n>> In fact, LEO satellites do not require these sorts of antenna systems\n>> for reliable use. A beginner will be perfectly happy with, say, four\n>> elements on 2m and 6-7 on 70cm (assuming the use of low-noise preamps,\n>> which you are *crazy*to do without on long antennas, too). The beauty\n>> of this system is that if a high wind knocks it slightly out of whack\n>> in azimuth, it will not be the end of your satellite work: you'll just\n>> have weaker signals, not silence. The other beauty of this system is\n>> that it doesn't require an elevation rotor *at all*. Because the\n>> elevation pattern of the antennas will more-or-less fill the sky if\n>> you point the array up about 10-20 degrees (make it 10 if you have a\n>> clear horizon). Now, suddenly, you've avoided all the hassle of\n>> another rotor, you've made your array lighter and easier to work with,\n>> and you have way less of a demand on your pointing system. Heck, if\n>> you want to go ol' school, you can do the pointing yourself with a\n>> twist of the dial.\n>>\n>> These yagis do not need to be brilliantly built: mine were made with\n>> welding rod and pine wood. They had very strange lobes off the side,\n>> and all the rest, but they netted me lots of Q's and were very\n>> reliable.\n>>\n>> To be even more radical, I urge beginners to start with\n>> omni-directional antennas and low-noise preamps. A wire dipole or a\n>> vertical, both with almost no coax between them and the preamp, should\n>> hear 'stuff' really well. Not Q-5, but a start. Then use this as a\n>> baseline from which to compare the theoretical and real-world\n>> improvement you get with your yagi array. If you aren't getting\n>> improvement, then work out what's up.\n>>\n>> This is not an argument against long arrays. I'm building some that I\n>> bought from someone on this list around this time last year. I want to\n>> do some exotic stuff like work Russia over the pole on AO-07 or hear\n>> every last beep out of the newest cubesat. But I'm aware that in my\n>> windy region these are going to be a bear to keep in place. So I'm\n>> putting as much work into an omni array, too. I plan to transmit from\n>> the latter when things get too QRO.\n>>\n>> I guess in summary I'd say that in my opinion a big antenna array\n>> isn't like a high-power computer, which works the same as a\n>> lower-powered one, but has the umph when you need it; it is like\n>> buying a high-powered plane as a new pilot: significantly more\n>> challenging, and possibly leading to frustration.\n>>\n>> 73, Bruce\n>> VE9QRP\n>>\n>>     \n\n",
    "attachments": []
}