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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/WIN547D5KQKMIBCIIYIXFA25EXBEPGG6/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "WIN547D5KQKMIBCIIYIXFA25EXBEPGG6",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/KMU7PWXGI6OJ4VUKIBFC3CDAFTM2IYMA/?format=api",
    "sender": {
        "address": "gary_mayfield (a) hotmail.com",
        "mailman_id": "fe442cdc520e4857a9168b9182091295",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/fe442cdc520e4857a9168b9182091295/emails/?format=api"
    },
    "sender_name": "Gary \"Joe\" Mayfield",
    "subject": "[amsat-bb] Re: Arrow and ELK Comparative Antenna Tests",
    "date": "2011-04-25T12:18:05Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/KMU7PWXGI6OJ4VUKIBFC3CDAFTM2IYMA/?format=api",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "John,\n\n      Thank you for your objective, scientific comparison!  I eagerly await\nyour article in the AMSAT journal ;-)  This is really good stuff.  If your\ntest stand is still available there is one more thing I would dearly love to\nsee tested.  Antenna guru Kent Britain, WA5VJB, once commented the Arrow\nseemed to be designed for the elements to be insulated from the boom, and\nthere might be something to be gained from doing just that.  Testing the\nArrow with the elements in standard convention vs. insulated has been on my\nto do list ever since but I never seem to be able to get around to it.\n\n\tAgain just a thought, and thanks for your awesome work already!\n\n73,\nJoe kk0sd\n\n-----Original Message-----\nFrom: [email protected] [mailto:[email protected]] On\nBehalf Of John Kopala\nSent: Sunday, April 24, 2011 10:50 PM\nTo: [email protected]\nSubject: [amsat-bb] Arrow and ELK Comparative Antenna Tests\n\nOn Saturday, April 23, Pat Stoddard (WD9EWK) and I did some antenna testing\nin an attempt to answer \nthe questions about which is the best antenna for portable satellite\noperation.  We only tested the \nantennas in receive mode to determine their relative gain.  Time constraints\nprevented us from \nperforming additional testing to determine if the transmitted output was\nconsistent with the receive \ngain of the antennas.  For the time being we will assume (and we all know\nthe dangers of doing so) \nthat the transmit performance closely matches the receive performance.\n\nThe antennas tested were an Arrow (3 x 7 elements), an ELK (4 elements), a\nPortaFox configured for \n145/435 operation (4 elements), and a Home Brew 4 by 9 element \"arrow\"\nantenna.  The standard Arrow \nantenna was the only antenna equipped with duplexer, but not the basic\nduplexer which is installed \nin the handle.  We did not measure the insertion loss of the duplexer on the\nArrow antenna, but this \nwas obviously not a significant factor in the overall performance.  A\nduplexer could still be \nrequired depending upon the antenna chosen and the radio(s) to be used.\n\nUsing the Arrow antenna as the reference antenna and 145.300 MHz as our test\nfrequency, our \nmeasurements indicated that the Arrow and the ELK antennas had identical\ngain.  The PortaFox antenna \nshowed 2db less gain than the Arrow and the ELK.  The Home Brew 4/9 element\ncrossed yagi showed 2db \nmore gain than the Arrow and the ELK.\n\nOn 435.300 MHz, the Arrow antenna had 2db more gain than the ELK and 8db\nmore gain than the \nPortaFox.  The Home Brew 4/9 element had 3db more gain than the Arrow.\n\nAlthough the ELK antenna shows slightly less (2db) gain on 435.300 MHz, it\ndoes have one potential \nadvantage over the Arrow antenna.  With the ELK, transmit and receive are in\nthe same plane.  With \nany satellites that have linear polarized antennas, such as AO-27, SO-50,\nthe ISS  and maybe SO-67, \na crossed yagis can maximize the performance on one band while minimizing it\non the other.  That \ndoes not mean the Arrow won't work, as has been demonstrated by the\nthousands of satellite QSO's \nthat are made on a regular basis using Arrow antennas.  It just means that\nwhen you rotate the \nantenna to maximize the downlink signal, you may be significantly impacting\nyou uplink signal \nstrength in marginal situations.\n\nEven though a satellite may have a circular polarized uplink and downlink,\ndon't assume that the \norientation of your station antenna as horizontal, vertical, or something in\nbetween won't have a \nsignificant effect on your signal strength.  My experience operating\nportable with my home brew \nantenna has convinced me that my horizontally polarized Qagi should either\nbe remounted vertically \npolarized or replaced with a circular polarized antenna.  That is another\nongoing project.\n\nIn summary, unless you plan to build your own, the performance of the Arrow\ncrossed yagi antenna and \nthe ELK log periodic antennas are very comparable and should provide lots of\nsolid satellite contacts.\n\nThe overall results reflect the adage that bigger is better, but along with\nmore gain, you also get \na more bulky antenna that is harder to handle.  The home brew crossed yagi I\nbuilt for portable \noperation is tripod mounted, can be rotated on its axis, and disassembles\nfor storage in a roll up \ncase.  But because of its size, it would be very tiring to attempt to use it\nhand held for an \nextended period of time.  Pictures of the home brew crossed yagi antenna are\non my QRZ page.\n\nJohn Kopala\nN7JK\n_______________________________________________\nSent via [email protected]. Opinions expressed are those of the author.\nNot an AMSAT-NA member? Join now to support the amateur satellite program!\nSubscription settings: http://amsat.org/mailman/listinfo/amsat-bb\n\n",
    "attachments": []
}