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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/ELALZFT3DCC2ZDBBK2VTQTS2ZRMIHX6P/",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/",
    "message_id": "[email protected]",
    "message_id_hash": "ELALZFT3DCC2ZDBBK2VTQTS2ZRMIHX6P",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/TDD4W4VM2MV3DCIKTXHHMF7S62KC7LHW/",
    "sender": {
        "address": "kg0mw (a) greatplainsphotography.com",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "Chad Phillips",
    "subject": "[amsat-bb] Re: Thoughts on alternative eggbeater build/feeding",
    "date": "2008-01-27T21:10:07Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/OUF5HHJZ6QZBQFSREPTFNX26JSYRI4VO/",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Thanks for your thoughts Jonny. I am curious to see how that will work. \nI am in the process of totally rebuilding my station after 4 years qrt \nand am open to all the options. Egg Beater antennas are certainly on my \nlist of things to build. I LOVE my long boom yagis, but the EB's would \nbe fun to play with.\n\nChad\nkg0mw\nEn-13\n\n\n\njonny 290 wrote:\n> Ye olde bird nerds,\n>\n> I was sketching out some plans to rebuild my practically-failed \n> Eggbeater antenna project for\n> 70cm, as I am tired of cranking the rotator knob every pass and want to \n> try out a good omni satellite antenna, which I\n> can hang from the top limb of a tree 30 feet above my shack window (best \n> option on my city lot).\n>\n> My plan is to build on the K5OE Eggbeater II antenna. One thing that's \n> always bugged me about these antennas\n> is that most are implemented using a 93 ohm coaxial section to phase the \n> loops. This is hard stuff to find, and though\n> I know some hams say, \"anything below 1.5 SWR is OK\", I'm a \n> perfectionist and want to try to polish it up.\n>\n> The current antenna has a phasing section made out of two runs of RG-8X \n> coax with the shields shorted and insulated, centers fed as a balanced \n> 100 ohm (theoretical) matching section. It was difficult to build and I \n> doubt its integrity because it's coiled up so tightly;\n> I don't think that the foam core coax retains its impedance well when \n> folded up in 1\" PVC.\n>\n> I was thinking about the feeding issues, then I recalled that one \n> popular CP yagi antenna design is to space the horizontal and vertical \n> elements 1/4 wavelength along the axis, and then feed them in phase.  It \n> then came to me that it may be possible to build an eggbeater with the \n> two elements separated vertically by 1/4 free space wavelength, fed with \n> simple half-wave coax sections to replicate the two loops' 100 ohm \n> impedance into a simple coax tee.  Polarity switching should be possible \n> with a coax relay and a 1/2 wavelength delay line. Radials would be \n> placed 1/4 wave apart as well, same spacing as the loops.\n>\n> The advantages of this to me seem numerous. First of all, the free space \n> quarter wavelength spacing is easier to accurately implement than a 1/4 \n> wave phasing section using coaxial cable at 70cm, and the \n> power/currents/etc split to the two antennas are more balanced as long \n> as you build the 1/2 wave sections to equal lengths, leading to improved \n> circularity skyward. You don't need to find rare coax for the phasing \n> section, and instead of cramming several folded up or coiled runs of \n> coax inside a narrow (for aesthetics) PVC tube, you only need to run two \n> half-wavelength (or any multiple of half-wavelength) runs further down \n> the mast, where the tee or relay could be ziptied.\n>\n> So, that's my plan. If it makes sense, I'm going to give it a shot with \n> 1/4\" copper fridge tubing for the loops and some sort of sturdy wire \n> (coathangers? heh) for the radials, using LMR240 coax for the two \n> halfwave sections. If anybody has any input or comments, I'd love to \n> hear them.\n>\n> (P.S. If somebody's done this and I'm reinventing the wheel, please let \n> me know. :) )\n>\n> Matt\n> KC4YLV\n>\n> _______________________________________________\n> Sent via [email protected]. Opinions expressed are those of the author.\n> Not an AMSAT-NA member? Join now to support the amateur satellite program!\n> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb\n>\n>\n>   \n\n\n",
    "attachments": []
}