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{ "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/2IOCSGZSQQL44M7X4537HYJVO42JJGKP/?format=api", "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api", "message_id": "CAHD9BgCCy14Rb2mMFoYKLN3dwnxu=TNpLycLqY90ZkFktNqKrw@mail.gmail.com", "message_id_hash": "2IOCSGZSQQL44M7X4537HYJVO42JJGKP", "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/6VKSY2YUOJBL374MDTP74B2LXFYTBD44/?format=api", "sender": { "address": "jmtrewitt (a) gmail.com", "mailman_id": "967d8763674b4978825e6fecd813ed3d", "emails": "https://mailman.amsat.org/hyperkitty/api/sender/967d8763674b4978825e6fecd813ed3d/emails/?format=api" }, "sender_name": "Jordan Trewitt", "subject": "[AMSAT-BB] Re: Helix for 1.2/2.4 GHz", "date": "2021-03-01T14:53:21Z", "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/B5YEHMQKGNQHUZCNWI5L6BINFJERIR6G/?format=api", "children": [], "votes": { "likes": 0, "dislikes": 0, "status": "neutral" }, "content": "You're almost tempting me to buy some of the fancier 3D printer filaments\nwith known dielectric values.\nhttps://www.preperm.com/webshop/product/preperm-3d-abs-ɛr-3-0-filament/\n\n*Dielectric constant* Loss tangent\n*2.4 GHz* *22 GHz* *60 GHz* *2.4 GHz* *22 GHz* *60 GHz*\nPPE260 2.60 2.60 2.58 0.0009 0.0022 0.0025\nPPE300 3.00 3.00 2.99 0.0009 0.0022 0.0025\nPPE320 3.20 3.20 3.19 0.0009 0.0024 0.0026\nPPE350 3.50 3.50 3.49 0.0009 0.0024 0.0026\n\nThe main reason I think I'd want to try helix on a pipe or 3D printed\ncylinder, is more because you can use flat copper tape, as I understand it\nshould increase the bandwidth if it's done right (big if?). I did get bored\none evening and at least tried to print the tallest helix I could make on\nmy printer a few weeks ago, but I still need to get around to finishing the\nSMA connection feed.\n\nI really need more excuses to buy one of those nanoVNAs anyways.\n\nregards,\n\nJordan\n\nKF5COQ\n\nOn Sun, Feb 28, 2021, 13:03 KENT BRITAIN <[email protected]> wrote:\n\n> Hi Jerry\n>\n> I have taken an antenna range to over 60 conferences. And done quite a\n> bit or work with Helix antennas at my lab. Of the 100 or so Helix's I have\n> tested, only about 10% were circularly polarized.\n> That's right, only about 1 in 10. I have proven many many times, HAMS\n> CANNOT BUILD CP HELIX ANTENNAS!\n>\n> It is amazing how a Helix Antenna can have an Axial Ratio of over 20 dB.\n> That's about the same axial ratio as you get from many Yagi's. The\n> few helix's that worked were usually built by a professional in the field.\n>\n> Unless you have actually tested your Helix on a range, the chances are\n> about 9 out of 10 is it not CP\n> (Yes, it is a valid statement that all antennas are ellipticaly polarized,\n> CP and Linear are just special cases.).\n>\n> As an example, the wave comes down the helix, hits the tip, them reflects\n> as a standing wave on the helix structure with an opposite CP sense.\n> You can put a helix antenna on an antenna range, then start trimming the\n> tip with some wire cutters a few millimeters at a time. The Axial ratio\n> will be constantly changing. You can, with some experimenting, find the CP\n> point, but statistics are against you without any testing.\n>\n> And the Kraus Formulas are about 3 dB Optmistic.\n>\n> Winding the helix on a plastic pipe creates all sorts of problems. In\n> free space the radio wave travels along the wire at about 95% the speed of\n> light. When you wrap the wire on a plastic tube, the velocity factor is\n> now about 60%.\n> The effective length and turns ratio is completely different from the\n> calculations. And darn near impossible to even simulate What is the\n> dielectric constant of that plastic you got at the hardware store? And\n> If you did look up the Er, that value was measured at 1kHz, not 1269 MHz!\n> So unless you actually measured the Er at 1269 MHz, your CST, HFSS,\n> OPENEMS, etc simulation is not valid.\n>\n> Sam, G4DDK was the first to measure the effects of using just one\n> dielectric boom with the helix winds attached directly to the boom. i.e.\n> one boom and the helix turns attached to the boom at their 12 O'clock\n> position.\n> The dielectric effects of the boom tilts the beam in the direction of the\n> boom.and really reduces the gain of long helix antenna.\n>\n> The NASA way, central boom and spokes to support the helix is by far the\n> best way to go.\n>\n> 73 Kent WA5VJB\n>\n>\n>\n> On Sunday, February 28, 2021, 01:39:25 PM CST, <[email protected]> wrote:\n>\n>\n> Build one myself for 23cm years ago on 1268Mc. 2*19el fixed RHCP. The\n> tricky part was the DR environment because spacings are small on 23cm.\n> Made it with 1/4L mechanical spacing. It never lead me dwn, worked beter\n> then my 30t helix.\n> I hope my 4pol switch for this crossyagi will be finished in a month or 2,\n> but busy with building µwave EME setup.\n> Maybe i will try it first with my 70cm 4pol switch, but this will have\n> more loss.\n>\n> I've never seen commercial crossyagis for 23, but WIMO used to have helix\n> antennes for 23c,and 13cm, or try to make them yourself.\n>\n> best 73's\n>\n> Jerry,ON4CJQ\n>\n> ----- Oorspronkelijk bericht -----\n> Van: \"amsat-bb\" <[email protected]>\n> Aan: \"amsat-bb\" <[email protected]>\n> Verzonden: Zondag 28 februari 2021 11:41:35\n> Onderwerp: [AMSAT-BB] WTB: Circular Polarized Yagis for 1.2/2.4 GHz\n>\n> Trying to locate a good source for these. M2 doesn't have these. Ideas\n> pls?\n>\n> 73/Ed NI6S\n>\n> -----------------------------------------------------------\n>\n> Sent via AMSAT-BB(a)amsat.org. 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>\n> View archives of this mailing list at\n> https://mailman.amsat.org/hyperkitty/list/[email protected]\n> To unsubscribe send an email to amsat-bb-leave(a)amsat.org\n> Manage all of your AMSAT-NA mailing list preferences at\n> https://mailman.amsat.org\n>\n>\n> -----------------------------------------------------------\n>\n> Sent via AMSAT-BB(a)amsat.org. 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>\n> View archives of this mailing list at\n> https://mailman.amsat.org/hyperkitty/list/[email protected]\n> To unsubscribe send an email to amsat-bb-leave(a)amsat.org\n> Manage all of your AMSAT-NA mailing list preferences at\n> https://mailman.amsat.org\n>\n> -----------------------------------------------------------\n>\n> Sent via AMSAT-BB(a)amsat.org. 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>\n> View archives of this mailing list at\n> https://mailman.amsat.org/hyperkitty/list/[email protected]\n> To unsubscribe send an email to amsat-bb-leave(a)amsat.org\n> Manage all of your AMSAT-NA mailing list preferences at\n> https://mailman.amsat.org\n\n\n", "attachments": [ { "email": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/2IOCSGZSQQL44M7X4537HYJVO42JJGKP/?format=api", "counter": 2, "name": "attachment.html", "content_type": "text/html", "encoding": "utf-8", "size": 15430, "download": "https://mailman.amsat.org/hyperkitty/list/[email protected]/message/2IOCSGZSQQL44M7X4537HYJVO42JJGKP/attachment/2/attachment.html" } ] }