Email Detail

HTTP 200 OK
Allow: GET, HEAD, OPTIONS
Content-Type: application/json
Vary: Accept

{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/YM6HZUC7ET3DP2HXCOEAOVRMQ3LNPGT6/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "YM6HZUC7ET3DP2HXCOEAOVRMQ3LNPGT6",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/YM6HZUC7ET3DP2HXCOEAOVRMQ3LNPGT6/?format=api",
    "sender": {
        "address": "nsp25 (a) cornell.edu",
        "mailman_id": "013b724c0f5242a785b441fc3ae1038c",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/013b724c0f5242a785b441fc3ae1038c/emails/?format=api"
    },
    "sender_name": "Nathaniel S. Parsons",
    "subject": "[amsat-ne]  Cornell Satellite Team Needs Help",
    "date": "2008-04-21T01:32:33Z",
    "parent": null,
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Hello everyone,\n\nI am a student at Cornell University, and a member of the Cornell\nUniversity Satellite Project Team (http://cusat.cornell.edu).  We are\npreparing for a launch in June, but problems were found with our RF\nsystem, so I'm trying to solicit help from those with experience,\nexpertise, and/or equipment related to spacecraft\ncommunication/antenna design on the amateur 70-cm band. If you have\nany or all of this, please read on.\n\nSome backstory: last year, we won the University Nanosat-4\ncompetition, and the prize was a free launch.  Right now, we are\naiming to be put on the next launch of the Falcon 1 rocket by SpaceX.\nBoth parts of the satellites have been assembled, and are undergoing\nfurther testing with the AFRL in Albuquerque.  While that seems to be\ngoing along well, our latest test of the RF system doesn't look good,\nand we don't have the equipment or expertise to correctly diagnose the\nproblem or find a solution, nor do we have much time.  So, I apologize\nif this email is rather disjointed, but there are many things going on\nat once. I'll be glad to clarify anything I can. Also, I think it\nwould be best if you assumed that we don't know anything about\nanything, because something that is obvious to you may not be very\nobvious to us.\n\nThe problem surfaced on Friday, when we performed a ridge test to\nverify that our RF system was adequate, and found out that it is not.\nWe had a the satellite's antenna attached to a structural prototype of\nthe satellite, and brought it to a hill roughly 4km from our ground\nantenna. We stuck attenuators on the ground station, between the\nantenna and the pre-amp in order to simulate the path loss we would\nexperience in space (LEO, 330x685, 9.1 degree inclination), and\ntransmitted from the satellite.  By our calculations, we needed\nroughly 57 dB of attenuation in order to be confident that we could\nhear the satellite while it was at the edge of the horizon, but we\nlost signal after 10 dB. It is possible we made mistakes in the design\nor construction of the satellite's antenna, or in the configuration of\nthe ground station, so I would greatly appreciate if you could look\nover what we have and did, and see if you could point out what we've\ndone wrong, what we can do to further test this, and what potential\nsolutions are. If anyone is in the Ithaca area, I would be more than\nwilling to show you our setup.\n\nOn each satellite, we have two square loop antennas made of 12-gauge\ncopper wire, 8.3125 cm per side, corner fed.  At the feed point of the\nantenna, we have a matching circuit as follows:\n\n(antenna)-----------------------+----C2---+--------------TX/RX\n     |_________________C1______L________Ground\n\nC1=56uF\nC2=33uF\nL=10.7nH\n\nAccording to our EZNEC model, this comes pretty close to matching\nimpedence with our 50-ohm, RG316  coax, 1/2 wavelength long, which\nfeeds into a Kenwood TH-D7AG, modified to fit in a metal box suitable\nfor flight. For the test, we didn't use the flight radio, but\nconnected the same antenna to an unmodified TH-D7 held outside the\nprototype structure (if that has any significance). Since the best SWR\nmeter we have is an MFJ 269 we don't really know how to use, we have\nnot been able to verify that the antenna + matching circuit perform\nthe same as in the simulation, or have the same impedance.  I just now\nfound someone at Cornell with a network analyzer, and I hope he will\nlet me use it. What else should we do to test the antenna? Did we even\nchoose the 'right' kind of antenna for what we want to do?\n\nOn the ground station side, we have the following equipment:\n\nAntenna: M2 436CP30 70-cm, circularly polarized Yagi\nCoax: RG-8, 50 ohm\nPre-amp: KP-1-440 70 cm in-shack GaSa FET Pre-amplifier (Oops, just\nfound out from ARRL Handbook we need a mast-mounted one. What\nmast-mounted pre-amps are available for 70-cm? Can we simply weather\nproof what we have and stick it on the antenna's mast?)\nTransceiver: Kenwood TS-2000\nTNC: Kantronics KAM-XL\nRotator: G-5500 with GS-232B controller\nRotator control software: NOVA for Windows\nRadio control software: Ham Radio Deluxe\n\nUnfortunately we're not entirely sure about how to fully use all of\nour equipment, or if we're using them correctly.  It's possible that\nwe have something off and we aren't able to fully step back and see\nall the 'little things.'  Would it be possible for someone to take a\nlook at what we have and show us best practices and/or help us with a\nsanity check?  We can flip through several different manuals and check\ndifferent websites for help but it might be better to have some\ngrizzled experience working alongside us.\n\nThanks for any advice or help you can provide.  We're excited to be\nworking on this and learning as we go along, but we could really use a\nguided push towards success.\n\n73\n-Nate Parsons\nKC2SVI\n",
    "attachments": []
}