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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/2ZGSP3HSSJ7MUJTCH2V4QOLQUKELZBGC/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "2ZGSP3HSSJ7MUJTCH2V4QOLQUKELZBGC",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/IQ6AUXFAHKK33LH5WIDGTRV5IWJ62BC4/?format=api",
    "sender": {
        "address": "andres (a) msu.edu",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "STeve Andre'",
    "subject": "[amsat-bb] Re: Re HELIX REFLECTOR?",
    "date": "2010-06-05T21:10:57Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/XKLNTPYRTXIYRTRLZ3OIFM225AUWJ6DA/?format=api",
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/JDP2QNMGYFVYMCIS6XEV7UKNPLWU2KZ2/?format=api"
    ],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "john, whats a good rule for height of the antennas to avoid large\nback lobes reflecting, ie how many wavelengths up should the\nantennas be?  Thanks...\n\n--STeve Andre'\nwb8wsf  en82\n\nOn Saturday 05 June 2010 17:07:15 John Belstner wrote:\n> Just another $0.02 to add.\n>\n> You will find that the size and shape of the reflector will not affect the\n> forward gain as much as it does the F/B ratio.  It depends on what is\n> important to you and (of course) how high you are above the ground.  Even\n> for satellite operation pointing up, large back lobes reflecting off the\n> ground can adversely affect the forward pattern when the antenna is mounted\n> only 6-8 feet above ground.\n>\n> On Jun 4, 2010, at 10:13 PM, Clare Fowler wrote:\n> > To add to the discussion the July/Aug 2007 Amsat Journal has an article\n> > covering some gain comparisonmeasurements I made between four\n> > 13 turn (2.88 wavelengths) 13cm antennas  with different square solid\n> > aluminum reflectors.\n> > The sizes were 0.56 wavelengths, 0.84 wavelengths, 1.0 wavelength and 1.4\n> > wavelengths.\n> > There was no difference between the 0.84, 1.0 and 1.4 wavelengths but the\n> > antenna with the0.56 wavelength reflector had 1.5 db less gain.\n> >\n> > However for my 70cm helix antennas I followed the Satellite Handbook\n> > minimum\n> > size of 0.6 wavelengthsor slightly over 16 inches. I used 1/2 inch\n> > hardware cloth\n> > mesh to keep the weight and windloading down.\n> > These antennas have performed well however it appears that they would be\n> > a bit better with a somewhat larger reflector.\n> >\n> > A brief description and picture of the 70 cm reflector is in the\n> > November/December 2005 Amsat Journal article on\n> > The Development of a Quarter Wave Match for helical antennas.\n> >\n> > Clare  VE3NPC\n> >\n> >>> Hi All:\n> >>> I am rebuilding a 440 MHZ Helix that I built several years ago . It\n> >>> worked very well, but I would like to reduce the size of the reflector\n> >>> to a more manageable size than I had before. The only reference to\n> >>> reflector size I can find is, \"minimum 20\" \". I may be looking in the\n> >>> wrong places. I would appreciate it, if someone would steer me in the\n> >>> right direction. Thanks,\n> >>> Pete, K1HZU\n",
    "attachments": []
}