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{ "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/6OS3773LWSWWNAUSTPLOAYE6U2F3D672/?format=api", "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api", "message_id": "CACZz0S388LSC_TXCLqRA5GEYYUE8ZEH0K74dwpenGWSGB-xEZA@mail.gmail.com", "message_id_hash": "6OS3773LWSWWNAUSTPLOAYE6U2F3D672", "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/6OS3773LWSWWNAUSTPLOAYE6U2F3D672/?format=api", "sender": { "address": "ks1g04 (a) gmail.com", "mailman_id": "30590cddbe684a52a5c3c945059cdd06", "emails": "https://mailman.amsat.org/hyperkitty/api/sender/30590cddbe684a52a5c3c945059cdd06/emails/?format=api" }, "sender_name": "Stephan Greene", "subject": "[amsat-dc] Thank you & antenna links", "date": "2013-03-25T21:52:01Z", "parent": null, "children": [], "votes": { "likes": 0, "dislikes": 0, "status": "neutral" }, "content": "All:\n\nI had a great time at the AMSAT-DC meeting on Saturday. I greatly\nappreciated the contributions, ideas, and questions from all the\nparticipants. HUGE THANKS to Pat Kilroy and to NASA GSFC for hosting!\n\nSince I went on quite a bit about cheap antennas, here are some links to\ndesign & construction info and some related information.\n\nCheap Antennas for the AMSAT LEO's (WA5VJB)\nhttp://www.wa5vjb.com/references/Cheap%20Antennas-LEOs.pdf\nConstruction suggestions, tuning, diplexer design. Also discusses\nperformance of Arrow antenna.\n\nCheap Yagi for 70 cm (search Amsat.org or internet for the companion 2M\ndesign) - uses foam board!\nhttp://www.amsat.org/amsat-new/information/faqs/crow/JulAug06AmsatJournal.pdf\n\nControlled Impedance \"Cheap\" Antennas (WA5VJB)\nhttp://www.wa5vjb.com/yagi-pdf/cheapyagi.pdf\nThe original cheap yagi article. Designs for 2M, 220 MHz, 70cm, 902 MHz,\n1296 MHz, including AMSAT and FM sections on 70cm. Great ideas for\nterrestrial as well as satellite ground station antennas.\n\nThe 6 element 2M antenna I had with me on Saturday is VJB's 2M design and\nI've used it with reasonable success on 2M terrestrial (tropo, E-skip) and\nmeteor bounce (FSK441 using WJST software). It's probably about as large\nas I'd want to use for a VHF rover station or portable installation. It's\nlarger than necessary for use with LEO satellites; a much lighter boom & 3\nor 4 elements are more than sufficient. There have been several published\nhandheld designs that are 2 elements, and the Arrow (even with alleged\nperformance issues) is a 3 element design.\n\nWA5VJB Herringbone Log-Periodic for satellites:\nhttp://www.cq-vhf.com/vhf_highlights/2012_vhf/2012_spring_vhf/2012_spring_vhf_antennas.pdf\nInteresting design, simple, very portable (designed for hand-held).\n\nDK7ZB's designs. http://www.qsl.net/dk7zb/start1.htm\nHuge wealth of information here! Probably better performance than the\nWA5VJB designs, but more demanding of precise construction. Most of his\ndesigns are in metric units but some have English measurements as well.\n There are several standard inch dimension rods that are close enough to\nmetric sizes to work. And you can get metric-dimensioned components ,\ntoo. Many examples of ingenious construction techniques in the photos.\nHis area of interest in terrestrial weak-signal communications; many of his\ndesigns are VERY optimized for 144.2 MHz and 432.2 MHz, particularly the\nlower impedance designs. So stick with the smaller 50 ohm designs for\nsatellite use.\n\nThe 2M/70cm-Yagis Ultralight page is probably most useful for satellite\nantennas. http://www.qsl.net/dk7zb/PVC-Yagis/PVC-details.htm Many of the\ndesigns are available from SOTABeams (UK) http://www.sotabeams.co.uk and as\nkits from Attila Kocis DL1NUX, Nuxcom, http://www.nuxcom.de. Some\nsatellite-specific ideas & info:\nhttp://www.qsl.net/dk7zb/Cross-Yagi/crossyagi.htm\n\nUsing electric fence post insulators as element mounts (especially for\naluminum booms)\nhttp://www.qsl.net/dk7zb/images/Elementhalter/elementholder_fence.htm\nDK7ZB and WA5VJB both assume the antenna elements are insulated from the\nboom. If you use an aluminum boom (recycled antenna pieces, ¾\"x ¾\"\nextrusions from Lowes/Home Depot), you have to mount the elements above the\nboom or with insulated plugs through the boom (and worry about boom\ncorrection factors). These insulators are a good alternative. And I don't\nunderstand why the Europeans get all the cool design small parts. Less\nexotic looking ones are available on Ebay & Amazon (and probably at\nfarm/horse supply stores, Tractor Supply, etc.). I purchased a big bag of\nthem off Ebay and plan to experiment with this approach.\n\nAntenna element materials: WA5VJB recommends welding rod (cheap, elements\nmay require splicing with hobby tubing to get lengths for 2M), #10 solid\ncopper wire ($$), solid aluminum guy wire (old versions - Radio Shack\ndiscontinued the product several years ago), hobby tubing/rods (can get\n$$). Several online vendors sell a variety of aluminum rod and brass rod,\nsome will cut to custom length at small additional cost if you are as inept\nas I am with hand tools! Watch shipping charges if you go over 48\" in\nlength. On the 6 element 2M antenna I displayed, I spliced the 2M driven\nelement for that reason. The local big box stores generally don't stock\nsmall enough diameters/long enough lengths but it's worth a look. Or hit\nTimonium or Manassas and see what's in the flea market.\n\nInternet Vendors:\nhttp://ww.speedymetals.com\nhttp://www.onlinemetals.com (I think I ordered from them)\nhttp://www.mcmaster.com/#standard-aluminum-rods/=m17g2q [Thank you to\nSambudra for reminding me of M-C] McMaster-Carr sells the rod stock in 6ft\nlengths; I haven't checked if they have oversize shipping charges. They\nsell a lot more than just metals.\n\nThe above designs can make circularly polarized antennas. The 2nd set of\nelements is mounted at 90 degrees on the boom and is offset by ¼ wavelength\n(free space, I believe). It's fed in parallel with the 1st set. Since\nboth antennas are 50 ohm designs, there are at least 2 solutions to deal\nwith the parallel impedance:\n\n1. Make a matching harness from coax of carefully cut and assembled\nlengths.\n2. Purchase or build a power divider (both Directive Systems and M2\nAntennas sell them), use IDENTICAL lengths of 50 ohm feedline to the\nantenna feedpoints.\n\nNote - According to the Directive Systems website, the company has been\nsold and is in the process of moving to HAYMARKET VIRGINIA this week!\nhttp://www.directivesystems.com\n\nRF Connection (therfc.com) in Gaithersubrg MD is an excellent local source\nof feedline, connectors, couplers, and associated parts. He can also make\ncustom harnesses (those phasing lines). Attends all the local hamfests, so\ngood way to save on shipping large amounts of coax across the country.\n\nI did not discuss omnidirectional antennas. The quadrafiller helix and\nLindenblad were mentioned at the meeting, and Pat had a Lindenblad on\ndisplay. These antennas have a reputation as difficult to build. A\npassive Lidenblad design was published in QST (or maybe AMSAT journal) a\nfew years ago and looks much easier to build. No idea how well they\nactually perform. The local RF noise level is high enough that higher-gain\nantennas may be a requirement around the DC area.\n\nWB4APR has recommended for years using a low-moderate gain yagi elevated 15\ndegrees (some folks go for 20). Rotate in azimuth and don't worry about\nelevation - most passes are not close to overhead and the satellite spends\nvery little time there. And when it is close, the shorter range and path\nloss make up for the loss in antenna gain (at least for smaller antennas -\na very tight EME array is a different matter!)\n\nPreamps - besides the wideband RX-only model AMSAT sells, there are several\nsources mentioned on Saturday. Advanced Receiver Research's product list\nis here http://www.advancedreceiver.com/page2.html\n\nHope this is of use to folks and look forward to the next meeting & meeting\nyou on the air locally, and on the birds!\n\n73\nSteve, KS1G\nFM18 Herndon, VA\n\n-- \n-----------------------------------------------------------------------------------------------------------------\nSteve Greene [email protected] <kay ess one gee zero four>@gmail.com\n-----------------------------------------------------------------------------------------------------------------\n", "attachments": [] }