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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/EF326PSKLTOQ5ZUCOQSNQO4YSMB4UFSS/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "EF326PSKLTOQ5ZUCOQSNQO4YSMB4UFSS",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/FPL34UYW6JMK54PTTZKY7UUZEWXPGNBK/?format=api",
    "sender": {
        "address": "broberts (a) mta.ca",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "Bruce Robertson",
    "subject": "[amsat-bb] Re: Advice on antennas for working the LEO's",
    "date": "2007-02-22T17:10:52Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/FPL34UYW6JMK54PTTZKY7UUZEWXPGNBK/?format=api",
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/AV5GQUGFQ37NVAPJYHL3JBDAMMNGMPOI/?format=api",
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/7TUTVZQSXPGTOBYIZLWG36TCUYQ4BZAK/?format=api"
    ],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Quoting Gary McKelvie <[email protected]>:\n\n\n> Several people have suggested using a vertical antenna such as a \n> colinear. I have actually already tried this and the results are very \n> disappointing, which I put down to my location rather than anything \n> else as where I am is not particularly that good certainly form a \n> VHF/UHF point of view.\n\nGary:\n\nWe look forward to working you on this side of the pond. If I remember the\ndetails of this thread correctly, one of your design goals for this system\nis to not require preamps. I would venture to say that most every antenna\ndesign or recommendation pertaining to satellite work assumes low-noise\npreamps as close to the antenna as possible. This might explain the\ndifference between your experience and others' with vertical antennas. \n\nWhat I love about this aspect of the hobby is the experimentation. Though\nmy antennas are down right now, there have been many silent mid-Atlantic\npasses of VO-52 where I have amused myself by testing the minimum signal\nrequired for reception, used varying antennas, and switched in and out a\npreamp or two. Just me and an orbiting radio laboratory; thank you, ISRO!\n\nConducting such experiments with my pair of FT-817s and TS-2000 suggests\nthat a preamp is terribly important, especially for 70cm downlink\noperation. In fact, my 70cm preamp is an indoor model, and it *still* makes\na crucial difference. I think this is because the NF of these radios'\npreamps is just not devised for small-signal work. To put it more strongly,\nI would rather spend an evening doodling around on 70cm with a (indoor)\npreamp and a coathanger-and-bnc vertical than I would with my 8 element\nrotating outdoor beam and no preamp!\n\nYour high-gain, narrow bandwidth antennas will make up for this, of course.\nBut other beginners might be interested to know that by using preamps and\nshorter, wider bandwidth antennas it is possible to have exceedingly\nenjoyable LEO satellite operations with a single, azimuth-only TV-type\nrotor. The approach offers some advantages: such short antennas are also\neasier to build from scratch materials, easier to put up on in the air; and\nthe wide beamwidth of the antenna makes it possible to manually control the\nrotor without too much fuss. The advantage of your az/el system is that it\nwill be closer to HEO-ready when P3E and SSETI are launched next year.\nHowever, I venture to say that you really will need preamps then.\n\nI started out using HRD, but like others, I have found that recent versions\ndo not track SSB/CW correctly, and it seems that Simon's focus is now on\nthe latest digital Swiss Army Knife. If you have difficulties of this\nnature, try the demo of SatPC32 or other dedicated programs.\n\nAgain, for others with a different set of resources, there's a great\ndiscussion of why a fixed-elevation rotor system works well at:\nhttp://web.usna.navy.mil/~bruninga/rotator1.htm\nI would advise that homebrewers begin avoiding circular polarization and\nthe mechanical challenges that entails. Many of us have had good luck\nbuilding the so-called 'cheap yagis':\nhttp://www.wa5vjb.com/yagi-pdf/cheapyagi.pdf\nMy 70cm one is 8 elements; I found my 4 element 2m to be a bit\nunder-powered for receiving AO-7, but I had fun with it for 2 years!\n\n\n73, Bruce\nVE9QRP\n\n\n",
    "attachments": []
}