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{ "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/BEMUG47ACRQ443HPMRFHGFPU3MUA5UHZ/", "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/", "message_id": "[email protected]", "message_id_hash": "BEMUG47ACRQ443HPMRFHGFPU3MUA5UHZ", "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/XQWPDYW4IQM7MHJCHPEJ37LNY77UCBJI/", "sender": { "address": "w5did (a) amsat.org", "mailman_id": "8da25cae70294f3687f590ebe6fded03", "emails": "https://mailman.amsat.org/hyperkitty/api/sender/8da25cae70294f3687f590ebe6fded03/emails/" }, "sender_name": "Louis McFadin", "subject": "[eagle] Re: Eagle Microwave Antenna Arrays -- mechanical concepts", "date": "2007-03-23T16:15:54Z", "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/Z5SBCVBK6TP3HI3UH4GXDPCKPHZJAS5J/", "children": [], "votes": { "likes": 0, "dislikes": 0, "status": "neutral" }, "content": "Tom,\nAs far as how to assemble the array IE whether it's made of \nindividual cups, milled out of a solid block or as some have \nsuggested milled from a casting, that should be left to the \nimplementor. What we need now is a solid foundation to build upon. If \nyou can show how you will be able to drive this array, we can figure \na way to build it.\nStan and I have had some experience building patches on S band and we \nbelieve we can build C band patches. It's obvious that putting the \npatches in a hex array gets more for the same amount of real estate \nand therefore gets you more gain. Do you think you can come up with a \nway to drive a hex array or not is the question. It would seem be be \nmore symmetrical around the Z axis and therefore have less spin \nmodulation.\n\nFred Parker has been experimenting with castings for an S band array. \nHis casting is still rough but has promise. It has 1/2 inch under the \narray to put the amplifiers and phasing harness. The array looks like \nthis. We made a test casting. It weighs .8 Kg.\nWe will put some patches in and see how they work.\n\nOn Mar 23, 2007, at 1:22 AM, Tom Clark, K3IO wrote:\n\n> Back in Feb, Bob Davis wrote:\n>> Jim,\n>> I would like to add to the agenda: top-level antenna \n>> configuration. I've begun to seriously consider what to build for \n>> the Eagle mockup at Dayton. Several people exchanged antenna \n>> configuration sketches late last year (September 2006), and don't \n>> know if there was resolution on A sketch. Something must be \n>> baselined soon (maybe by mid-March)), if we're to have the mockup \n>> ready for mid-May.\n>> bob\n>> Robert Davis\n>> KF4KSS\n> Bob -- I finally \"got a round tuit\" on this topic :-[\n>\n> This applies to both the C-band and S2 phased arrays. Instead of \n> drawing the possibilities, I figured it was easiest to build (spare \n> no expense!) simple models and three possibilities are attached. \n> When we computed the needed array gain, we came up wanting about \n> 35-40 individual patch antennas (15-16 dB of array gain added to \n> ~5-6 dB of element gain for a single patch). The individual patches \n> will need to be about 0.7 wavelengths in diameter; my guess is that \n> the patch itself will be about ½ wavelength in size and it will sit \n> inside a \"cup\" cavity that is about ¼ wavelength deep. This cavity \n> (a.k.a. choke ring) will help minimize the mutual coupling between \n> the antennas. For the two frequencies, we have\n> S2 = 3400 MHz = 8.8 cm wavelength. Therefore the \"cup\" will be ~6.2 \n> cm diameter and ~2.2 cm tall.\n> C = 5800 MHz = 5.2 cm wavelength. Therefore the \"cup\" will be ~3.6 \n> cm diameter and ~1.3 cm tall.\n> We will want good symmetry in the array to make the phasing as \n> painless as possible. This led me to the 3 models I've attached:\n> \"Square\" is a 6x6 array (36 elements). I think I have \"invented\" a \n> nice way to do the phasing for a square array based on the Butler \n> combiner matrix (the antenna analog of the Cooley-Tukey FFT) which \n> looks like it will work well (meaning easy to phase to \n> electronically de-spin the antenna) on an 8x8 array and I think it \n> can be trimmed down to 6x6. Since the rows/columns are spaces 0.7 \n> wavelengths, the diagonal element spacing will be just one \n> wavelength, so we won't have much power wasted in sidelobes.\n> \"Hex\" is 37 element array that is the tightest possible packing. It \n> approximates a 4.2 wavelength dish in its properties. So far, I \n> have not yet \"invented\" a Butler-like matrix for a hexagonal array, \n> so I don't know how well it can be implemented.\n> \"Ehex\" extends the Hex geometry by adding 6 elements (total=43) for \n> a bit more gain, with a pattern more like a 4.6 wavelength dish.\n> Stan and Lew have suggested that the honeycomb structures might be \n> done on an NC mill, which could give us a good thermal radiating \n> surface. For the transmit phased array we have thought in terms of \n> a ~1 watt (RF) power amplifier at each patch. Depending on what \n> kind of DC => RF efficiency we can achieve, this will mean that we \n> will have 20-30 watts of heat to dump from the array.\n>\n> My idea, instead of milling a big block, was to use extruded \n> aluminum cups (something like http://www.zerocases.com/catalog/deep- \n> drawn-enclosures/round-precision-miniatures.html).\n>\n> Maybe we can chat about this Saturday at the DC AMSAT meeting --- \n> 73, Tom\n> <hex.jpg>\n> <Ehex.jpg>\n> <square.jpg>\n> _______________________________________________\n> Via the Eagle mailing list courtesy of AMSAT-NA\n> [email protected]\n> http://amsat.org/mailman/listinfo/eagle\n\n\n\n\n\n\n\n\n\n", "attachments": [ { "email": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/BEMUG47ACRQ443HPMRFHGFPU3MUA5UHZ/", "counter": 3, "name": "attachment.html", "content_type": "text/html", "encoding": "iso-8859-1", "size": 1364, "download": "https://mailman.amsat.org/hyperkitty/list/[email protected]/message/BEMUG47ACRQ443HPMRFHGFPU3MUA5UHZ/attachment/3/attachment.html" }, { "email": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/BEMUG47ACRQ443HPMRFHGFPU3MUA5UHZ/", "counter": 4, "name": "S1Arraycastingtop.JPG", "content_type": "image/jpeg", "encoding": null, "size": 92630, "download": "https://mailman.amsat.org/hyperkitty/list/[email protected]/message/BEMUG47ACRQ443HPMRFHGFPU3MUA5UHZ/attachment/4/S1Arraycastingtop.JPG" }, { "email": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/BEMUG47ACRQ443HPMRFHGFPU3MUA5UHZ/", "counter": 5, "name": "attachment.html", "content_type": "text/html", "encoding": "us-ascii", "size": 143, "download": "https://mailman.amsat.org/hyperkitty/list/[email protected]/message/BEMUG47ACRQ443HPMRFHGFPU3MUA5UHZ/attachment/5/attachment.html" }, { "email": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/BEMUG47ACRQ443HPMRFHGFPU3MUA5UHZ/", "counter": 6, "name": "S1ArrayBottom.JPG", "content_type": "image/jpeg", "encoding": null, "size": 110981, "download": "https://mailman.amsat.org/hyperkitty/list/[email protected]/message/BEMUG47ACRQ443HPMRFHGFPU3MUA5UHZ/attachment/6/S1ArrayBottom.JPG" }, { "email": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/BEMUG47ACRQ443HPMRFHGFPU3MUA5UHZ/", "counter": 7, "name": "attachment.html", "content_type": "text/html", "encoding": "us-ascii", "size": 193, "download": "https://mailman.amsat.org/hyperkitty/list/[email protected]/message/BEMUG47ACRQ443HPMRFHGFPU3MUA5UHZ/attachment/7/attachment.html" }, { "email": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/BEMUG47ACRQ443HPMRFHGFPU3MUA5UHZ/", "counter": 8, "name": "FredsS1antarray.pdf", "content_type": "application/pdf", "encoding": null, "size": 26362, "download": "https://mailman.amsat.org/hyperkitty/list/[email protected]/message/BEMUG47ACRQ443HPMRFHGFPU3MUA5UHZ/attachment/8/FredsS1antarray.pdf" }, { "email": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/BEMUG47ACRQ443HPMRFHGFPU3MUA5UHZ/", "counter": 9, "name": "attachment.html", "content_type": "text/html", "encoding": "iso-8859-1", "size": 4569, "download": "https://mailman.amsat.org/hyperkitty/list/[email protected]/message/BEMUG47ACRQ443HPMRFHGFPU3MUA5UHZ/attachment/9/attachment.html" } ] }
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