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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/7VUHQBUQIJPHILPIXQG3GAFQC332MF5X/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "7VUHQBUQIJPHILPIXQG3GAFQC332MF5X",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/V5GWGIGQDCHNOQACTVNBTDMJJYVEEPEV/?format=api",
    "sender": {
        "address": "vk4tec (a) people.net.au",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "Andrew Rich",
    "subject": "[amsat-bb] Re: [SPAM] Questions on physically offset CP yagi feeding",
    "date": "2007-12-25T00:50:21Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/V5GWGIGQDCHNOQACTVNBTDMJJYVEEPEV/?format=api",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Matt,\n\nI just made a 10 turn helix on 435 MHz and added a 15 db preamp from the\nlocal electronics store.\n\nI just copied genesat at S7\n\nI have never seen it so high.\n\nAwesome.\n\nMaybe you might like to try a helix >?\n\n\n\n----------------------------------------------------------------------------\nAndrew Rich VK4TEC\[email protected] <mailto:[email protected]>\nhttp://www.tech-software.net\n\n\n\n\n-----Original Message-----\nFrom: [email protected] [mailto:[email protected]]On\nBehalf Of jonny 290\nSent: Tuesday, 25 December 2007 7:59 AM\nTo: [email protected]\nSubject: [SPAM] [amsat-bb] Questions on physically offset CP yagi\nfeeding\nImportance: Low\n\n\nI've decided to rebuild my 2m antenna and have a couple of questions.\n\nI currently have vertically polarized yagis up for 2m and 70cm and they\nwork fine; however I am becoming more interested in weak signal work and\njust want to rebuild my antennas in general, as they need it after a\nyear. Due to necessity and environment, i can only have a few antennas\nup and have thought up a plan to meet all of my needs at a reasonable\nprice with only one cross yagi in the air.\n\nMy thinking is to build a six element wide-band 50 ohm match yagi and\nmount the vertically polarized elements 1/4 wavelength\nahead of the horizontal ones, and feed the elements in phase. I have\nexamined the possibility of masthead CP phasing, but am\nconcerned about mismatching and like the arguments given for the\nphysically offset, in-phase fed elements.\n\nMy antenna to radio coax run is right around 30 feet. I am thinking of\nrunning two lengths of LMR-240, speced at 3 dB loss/100ft, so loss\nshould be about 1 dB. If I cut the two feedlines to identical lengths, I\nshould be able to connect them with a coax tee in the shack and use a\n1/4 wave 37 ohm line to bring the system impedance back up from 25 (at\nthe tee) to 50 ohms. I'd then have an RHCP signal for the birds. Do I\n_need_ to cut the feedlines to half-wave multiples, or is it just a good\nidea? I plan on tuning the antennas as dead on to 145.8 as I can, so\nmismatch will be a minimum at that frequency.\n\nWhen I don't need RHCP, I can simply use the horizontal feedline for SSB\nwork and the vertical feedline for FM work, setting the coax tee\nnonsense aside. (as a note, the two sets of elements would be tuned\nidentically, centered for minimum swr on 145.8, but in my experience\noperation across the band is no problem).\n\nA good coax relay costs about 60-80 dollars and requires associated\nmounting hardware and weatherproofing, this only adds another $15 for 30\nmore feet of LMR240.\n\nAnybody care to share thoughts on this?\n\n73 and merry christmas\nmatt kc4ylv\n\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": []
}