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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/SEM4U4NPPRNLPUNKVLO36QRJAL6QL5X4/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "SEM4U4NPPRNLPUNKVLO36QRJAL6QL5X4",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/ICRAEUHQV7EZRA4RNBBCPWJSILTDWIRN/?format=api",
    "sender": {
        "address": "w2ev (a) yahoo.com",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "Ev Tupis",
    "subject": "Re: [amsat-bb] When exactly is a non-conductive mast necessary?",
    "date": "2019-12-31T11:09:17Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/7P3M33U7FMNL2TVYLMP6NETYUCZTVQDL/?format=api",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": " You've received some excellent information with that link to Kent's articles.\n\nIn regard to coax selection (not what you asked about, but some input you received), \"better is always better\", but the question becomes, \"How much better?\"\nThe answer is in the math.\nIf running the FM satellites from an HT and your coax is 3' from HT to antenna, using RG8x will result in 0.3 dB of attenuation at 70cm.  Using LMR-400 will be \"better\" at \"only\" 0.1 dB.  In the real world, the 0.2 dB difference is indistinguishable.\n\nMy point is not to contradict John's statement.  It is to add perspective and a pathway to allow you to decide what is best for your usage.\nCheers,Ev, W2EV\nhttps://www.timesmicrowave.com/Calculator\n\n\n\n\n    On Monday, December 30, 2019, 9:26:47 PM EST, John Kludt via AMSAT-BB <[email protected]> wrote:  \n \n Cathryn,\n\nAnd if you pay attention to all of the caveats in his paper.  One saving\ngrace about all of this is it is not EME.  If you were working with\n250 +/-  dB path loss and a passive reflector like the moon you might come\nto a different conclusion.  Just be careful of all of the those 1/2\nwavelengths and 1 wavelengths that he speaks about.  Especially for the 70\ncm uplinks as that isn't very many inches.\n\nThe other thing I have seen folks trip over is coax selection.  Satellites\nare not the place to be using RG-8X.  Others may have other thoughts I\nthink you are looking at LMR400 or its equivalent or better if it is a\npermanent installation.\n\nJohn\n\n\nOn Mon, Dec 30, 2019 at 7:57 PM Cathryn Mataga via AMSAT-BB <\[email protected]> wrote:\n\n> Oh, thanks guys. This is eye-opening.  It looks like even circular\n> polarized antennas will work with metal masts, if you rotate them 45\n> degrees.\n>\n>\n> On 12/30/2019 2:31 PM, Gary wrote:\n> > The short answer is almost never. Here is a link to an AMSAT Symposium\n> paper form antenna guru Kent Britain, wa5vjb (inventor of the famous cheap\n> yagis). He actually measured the effects.\n> > http://www.kk0sd.net/metalboom/metalboom.htm\n> >\n> >\n> > 73,\n> > Joe kk0sd\n> >\n> >\n> > -----Original Message-----\n> > From: AMSAT-BB <[email protected]> On Behalf Of Cathryn Mataga\n> via AMSAT-BB\n> > Sent: Monday, December 30, 2019 3:27 PM\n> > To: [email protected]\n> > Subject: [amsat-bb] When exactly is a non-conductive mast necessary?\n> >\n> > I'm trying to understand, under what circumstances is a non-conductive\n> mast necessary at VHF/UHF frequencies. Thinking of the following installs.\n> >\n> > 1.  Circular polarized antenna mounted to the mast at the center of the\n> boom.    This is clear, see this advice all the time, fiberglass mast.\n> >\n> > 2. Same antenna but mounted at the rear end of the boom.\n> >\n> > 3.  Vertical Yagi, elements parallel to a vertical mast, mounted at the\n> center of the boom. I guess, non-conductive wold be required here.\n> >\n> > 4.  Same antenna but rear mounted.\n> >\n> > 5.  Horizontal Yagi, elements perpendicular to a vertical mast, mounted\n> at the center of the boom.  I think this is pretty normal install, so a\n> conductive mast would be okay?\n> >\n> > 6. Same antenna but mounted at the rear of the boom.\n> >\n> > _______________________________________________\n> > Sent via [email protected]. AMSAT-NA makes this open forum available\n> to all interested persons worldwide without requiring membership. Opinions\n> expressed are solely those of the author, and do not reflect the official\n> views of AMSAT-NA.\n> > Not an AMSAT-NA member? Join now to support the amateur satellite\n> program!\n> > Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb\n> _______________________________________________\n> Sent via [email protected]. AMSAT-NA makes this open forum available\n> to all interested persons worldwide without requiring membership. Opinions\n> expressed\n> are solely those of the author, and do not reflect the official views of\n> AMSAT-NA.\n> Not an AMSAT-NA member? Join now to support the amateur satellite program!\n> Subscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb\n>\n_______________________________________________\nSent via [email protected]. AMSAT-NA makes this open forum available\nto all interested persons worldwide without requiring membership. Opinions expressed\nare solely those of the author, and do not reflect the official views of AMSAT-NA.\nNot an AMSAT-NA member? Join now to support the amateur satellite program!\nSubscription settings: https://www.amsat.org/mailman/listinfo/amsat-bb\n  \n",
    "attachments": []
}