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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/BS6HOGSWL52QFPTW376JKJZOWGZZPSWE/",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/",
    "message_id": "CAF3DnKi6af_6AVYRhe37iRFYQ8uVOUer+d1w2Vq-gPPscJiH3Q@mail.gmail.com",
    "message_id_hash": "BS6HOGSWL52QFPTW376JKJZOWGZZPSWE",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/IEBVFI3OXF6552GSZZ24A2EWJ5B62A4I/",
    "sender": {
        "address": "dan (a) post.com",
        "mailman_id": "8fbd55eb51ed4663a4067933c1d26387",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/8fbd55eb51ed4663a4067933c1d26387/emails/"
    },
    "sender_name": "Daniel Cussen",
    "subject": "Re: [amsat-bb] CP vs. LP and all that implies",
    "date": "2015-01-22T10:29:13Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/IEBVFI3OXF6552GSZZ24A2EWJ5B62A4I/",
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/PARHNKKNINTUIX7EAYYG7243JY3YXPVD/"
    ],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Best info on-line I found here:\n\nhttp://sv1bsx.50webs.com/antenna-pol/polarization.html\n\nNote the losses of having the wrong circular polarisation from a\npolarised source are very high. In the real world the antenna may not\nbe perfectly polarised on one end, so difference may not be as great.\n\nOne very useful/recommended setup for circular is school contacts on 2\nmetres with the space station. It is recommended to be able to switch\npolarisation in the middle of a school contact as sometimes the signal\nis not direct but reflected off a solar panel. In this case you may\nneed to suddenly switch polarisation.\n\nI have a wimo 2m 6 element X circular antenna with the switching kit.\nThe antenna is extremely light and designed to be mounted at the very\nrear, to prevent the boom interfering in the signal. I was not that\nimpressed by the elements strength, guessing a bird might be able to\nbend them by landing on them. The driven element is made from a few\nparts screwed together. I worry corrosion would quickly make it\nunreliable. Being limited to 6 elements and quite short a longer\nlinear model may work nearly as good.\n\nhttp://www.wimo.de/xquad-antennas_e.html\n\nalso:\n\nhttp://www.wimo.de/power-splitter-combiner_e.html#18038\n\nThe 70cm model I have heard is much better in that the driven element\nis stamped rather than assembled so less joins to corrode. Also being\nsmaller the elements are stronger.\n\nThe switch box is designed to be mounted on the mast near the antenna\nmeaning only one coax cable per band needs to be ran out, but then you\nneed DC multicore to switch polarisations. You can select V, H, LHCP,\nRHCP. One downside is that they do not give the option of a control\nbox, so you need to build one by hand. You need to ensure you do not\ntransmit while switching.\n\nAll in all it is quite expensive, complicated and messy. Unless you\nhad an inferior setup, and found it lacking I probably would not\nbother. You only lose 3dB using linear when the source is true\ncircular, so probably not really worth it unless you have maxed out on\nantenna gain/ receive pre-amps. There are additional losses with\nswitches connectors etc.\n\nI have never seen/used the M2 setup so I cannot comment on this. They\ndefinitely seem to have more elements as a possibility.\n\nAt least with the switching option you can compare the signal on\ndifferent polarisations to see if it does help in the real world. You\ncould always try it on one band, then apply it to both bands if you\nget a big difference.\n\nWhat do others think?\n\nDan EI9FHB\n",
    "attachments": []
}