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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/QGC2DENEKMRI76BFQXKPHMIERT2DB2XL/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "729F120613BA471ABF380AF3BAC946B3@KC6UQH",
    "message_id_hash": "QGC2DENEKMRI76BFQXKPHMIERT2DB2XL",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/TJCL6FKIXEAHQNZWCFLTMLSMQSZALZ5X/?format=api",
    "sender": {
        "address": "kc6uqh (a) cox.net",
        "mailman_id": "d9201820d18047e4a2772c86bda5e111",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/d9201820d18047e4a2772c86bda5e111/emails/?format=api"
    },
    "sender_name": "Art McBride",
    "subject": "[amsat-bb] Re: QFHA for SO-50... polarization issue ???",
    "date": "2013-02-18T18:32:02Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/TJCL6FKIXEAHQNZWCFLTMLSMQSZALZ5X/?format=api",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Ing. Pavel,\n\nThere are a whole series of QFH antennas. 1/4,turn, 1/4 wavelength through 1\nturn 1 Wavelength. \nGain at the horizon is determined by the ratio of the axial length in\nfractions of a wave length. The best performance I have obtained is a 1\nwavelength per side, 1 turn, for good gain at the horizon with an axial\nlength of .65 wavelengths. You need the least gain at the Zenith as the\nsatellite is closest in range at that point.\n\nThe best reference I found is \"Resonant Quadrifilar Helix Design\" by C.C.\nKilgus, December 1970 Issue, of the Microwave Journal, Pgs 49-54.\n\n73,\nArt KC6UQH \n\n\n\n\n\n\n-----Original Message-----\nFrom: [email protected] [mailto:[email protected]] On\nBehalf Of Ing. Pavel Milanes Costa\nSent: Saturday, February 16, 2013 8:22 PM\nTo: [email protected]\nSubject: [amsat-bb] QFHA for SO-50... polarization issue ???\n\nThis weekend I tested a Quadrifiliar Helicoidal Antenna for 70cm (LHCP)\n\nI designed it by the online calculations of jcoppens on the internet...\n\nIt is a 1/2 turn and 1 lambda, about 5 meters of elevation with ~25 cm \nof RG-58U (a section of it is coiled to form a balum) and then ~15 \nmeters of A.H. LDF4-50A down to the shack directly to the radio, of \ncourse BNC to N adapter on the antenna and N to PL259 on the radio \nside... It's at mast top.\n\nResults are good... In passes of over 20 degrees (almost the real \nhorizon here) I have a good copy, until... TCA, in which I lost the \nsignal completely...\n\nTCA = Time of Closest Approach.\n\nIn northbound passes (I've not tested it in southbound) it work as I \njust said...\n\nI have been reading and investigating this strange issue and I think it \nis due to polarization...\n\nI had read that SO-50 is linear polarized on 2m AND 70cm with aprox 45 \ndegrees each other...\n\nThen Linear to LHCP in the worst case is 3dB loss (half power) but \nconsistent over the entire pass... or have SO-50 some \ncircular/elliptical component in it's signals that renders useless the \nantenna after TCA? spin maybe?\n\nThere is any chapter of the book I missed or other variable(s) that I \nhave not taking into account here?\n\nAny comment, link or other kinds of help are welcomed..\n\n73 de CO7WT.\n\n",
    "attachments": []
}