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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/S3QNWGANF6CHMYLKQLPKY2VLVX3JKV5T/",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/",
    "message_id": "[email protected]",
    "message_id_hash": "S3QNWGANF6CHMYLKQLPKY2VLVX3JKV5T",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/XJQD5OAWRSPADLXM2OPYVVKCWMP7IYYY/",
    "sender": {
        "address": "broberts (a) mta.ca",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "Bruce Robertson",
    "subject": "[amsat-bb] Re: ARRL dual moxon turnstyle project questions",
    "date": "2007-08-03T18:47:54Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/XJQD5OAWRSPADLXM2OPYVVKCWMP7IYYY/",
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/R2RMB7MQGONWDQALLZDMXPDT3UHHC44W/"
    ],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Quoting \"Reicher, James\" <[email protected]>:\n\n> Scott, \n> \n> 1. I would recommend using standard connectors and teeing them rather\n> than soldering to a lug.  You'll find that if you want to move the\n> array\n> for portable work, it will be easier to set up and take down.\n> \n> 2.  Although I'm no expert, I wouldn't think you'd even need the same\n> length feedline, although it couldn't hurt.\n> \n> 3.  LB gives the dimensions in inches, but try converting them to\n> millimeters.  Just multiply by 25.4 millimeters to the inch.  I'd round\n> to the nearest 1/2 mm and cut as close as possible.  Then, that \".49\n> inches\" dimension becomes 12.5 mm.  \n> \n> 4.  You could always use duct tape... they use it on the shuttle and\n> ISS!\n> \n> \n> BTW, the 70cm version calls for #12 AWG wire, not #14.  \n> \n> \n> 73 de N8AU, Jim in Raymore, MO\n>  \n> Light travels faster than sound...  This is why some people appear\n> bright until you hear them speak.\n> \n> \n> Date: Tue, 31 Jul 2007 07:08:16 -0700 (PDT)\n> From: Scott Wilson <[email protected]>\n> Subject: [amsat-bb]  ARRL dual moxon turnstyle project questions\n> To: [email protected]\n> Message-ID: <[email protected]>\n> Content-Type: text/plain; charset=iso-8859-1\n> \n> I'm working on building the ARRL dual moxon antennas, but the article\n> isn't very detailed where I'd like it to be and a little over detailed\n> in\n> some places I wish it weren't.\n> \n> If you want to look, this is the URL\n> (http://www.arrl.org/members-only/tis/info/pdf/0108038.pdf)\n\nScott:\n\nL.B. is a constant and reliable source of wisdom when it comes to antennas.\nI've built many of his designs, most recently a 7 element version of the\nOWA yagi for 2m. However, I have read a cogent criticism of these moxons,\nand I feel I should share it here. \n\nFor a fixed satellite antenna, the ideal pattern should provide diminishing\ngain as elevation rises. It should not null out as quickly as a 1/4 wave\nvertical, but certainly should have less gain overhead, where the bird's\nsignal will be many dB greater due to lower 'path losses' and where you\nwill rarely encounter the bird anyway. \n\nNote that these moxons do not fulfill this requirement: in fact, the\ngreatest gain is right overhead. For this reason, I would not build these\nantennas, despite the imprimatur of QST. Tony's lindenblad published in\nAugust 2007 QST would be a *much* better choice. (A 435MHz sister antenna\nto it can be found from the same source in the 2006 AMSAT symposium\npublication.) I'll guess that even a 1/4 wave might make a more practical\nantenna.\n\nYou joke that a $1000 rotor/yagi setup starts to seem like a good idea. I\nknow how you feel, but I think it is important that all newcomers to this\nfield understand that such commercial solutions are really, really\nunnecessary, especially for today's LEOs. A cheap tv-duty rotor can\neffectively turn a small pair of yagis, say 4 elements on 2m and 6-8 on 435\nMHz. The beamwidth of these is large enough that the rotor can be touched\nup every three minutes or so. Many, including myself, have found Kent\nBritain's 'Cheap Yagis' design to work well in this application. Total\nbudget: $90, I'd say.\n\nIn fact, such a set-up is *better* for the newcomer than a full-up pair of\nlong yagis with az/el rotor. Why? Well, if your yagis are not pointed dead\nat the bird, you'll have worse performance than with shorter ones. So\nyou've got to keep making sure that the az/el rotors are well-aligned, etc.\nThis is difficult and not particularly fun.  \n\nSecondly, with so much gain on uplink, you run the risk of swamping the\nreceiver of a linear bird such as VO-52 or AO-7. This creates a sort of\narms-race situation, where everyone else has to use equal effective power,\nor their signals don't get heard, and some QRP stations just fade away. We\nall make mistakes from time to time, but in my experience, the operators\nwho consistently run many s-units over the beacon are also frequently in\npossession of long antennas, and perhaps simply can't turn down their\ntransmitters sufficiently.\n\nYou might wonder why many people here, including myself, talk about our\nmore elaborate stations. Well, I'm struggling to add effective elevation\ncontrol (on a budget) and longer antennas because I'm attempting slowly to\nupgrade to a station that could operate the HEOs when they arrive. Others\nstill have HEO-grade stations from those days and use them for the current\nLEOs. I've enjoyed the technical challenge of upgrading, but truthfully I\nworked way more satellite DX with the simple station described above than\nwith my much-tweaked more elaborate one.\n\nFinally, I'm going to run off and spend half of that $1000 you mentioned.\nThe best use of it is on brand-name mast-mounted preamps. ARR or SSBUSA.\nDon't even think of receiving 435MHz without one. On 435MHz, I'd rather\nhave a paperclip as an antenna and a preamp than the biggest yagi without a\npreamp. In fact, my first satellite antenna was a 435MHz groundplane\nsoldered on a bnc connector. Hooked up to a good preamp, it hears LO-19\nwonderfully, even while indoors! \n\n73, Bruce \nVE9QRP\n",
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}