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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/MTBDF3PG7VQQFDEJZIWWIPBRH4ASKCHB/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "MTBDF3PG7VQQFDEJZIWWIPBRH4ASKCHB",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/TJCL6FKIXEAHQNZWCFLTMLSMQSZALZ5X/?format=api",
    "sender": {
        "address": "oz1my (a) privat.dk",
        "mailman_id": "b2f56900318d4d1193159750f39aa3fe",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/b2f56900318d4d1193159750f39aa3fe/emails/?format=api"
    },
    "sender_name": "Ib Christoffersen",
    "subject": "[amsat-bb] Re: QFHA for SO-50... polarization issue ???",
    "date": "2013-02-18T20:15:57Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/TJCL6FKIXEAHQNZWCFLTMLSMQSZALZ5X/?format=api",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Hi Pavel,\nThe issue may not be the antenna - but SO-50.\nThe antennas are linear - but the received signal strength can vary a lot if\nyou have just RHCP or LHCP.\nDuring passes here in Copenhagen, Denmark I experience large differences in\nsignal strength which can be counteracted by changing polarity from RHCP to\nLHCP during the pass.\nWith large changes I mean from nothing to 59 signals.\nHope that helps.\n73 de OZ1MY/Ib\n\n-----Oprindelig meddelelse-----\nFra: [email protected] [mailto:[email protected]] På vegne\naf Ing. Pavel Milanes Costa\nSendt: 17 February 2013 05:22\nTil: [email protected]\nEmne: [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\n",
    "attachments": []
}