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/MUEKS64MQKGLX33KN7Z7P3GITAEFNEUB/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "MUEKS64MQKGLX33KN7Z7P3GITAEFNEUB",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/UADPJ2VQ2C65E6QYNMVNYV3YIMVTUMKU/?format=api",
    "sender": {
        "address": "broberts (a) mta.ca",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "Bruce Robertson",
    "subject": "[amsat-bb] Re: Digital modes and antenna questions",
    "date": "2007-04-28T19:27:18Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/UADPJ2VQ2C65E6QYNMVNYV3YIMVTUMKU/?format=api",
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/JUIXC5RCOOBMHKDFWN4T6MORIGGS4AUJ/?format=api"
    ],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Quoting Stargate <[email protected]>:\n\n> Hi,\n> \tCan someone point me to a website that explains the current digital\n> modes\n> and ways to use them?\n> Also decoding telemetry from the birds, is there a \"one size fits all\"\n> software or does each satellite\n> have specialized software for doing this?\n> Can you use Sound cards, TNC, specialized modems?\n> I keep seeing references to 9K6, 38k6, and the like and have no idea\n> what\n> they are.\n> \n> \tAlso, are TNC's really necessary anymore? I've been away from amateur\n> radio\n> for over 10 years\n> and things sure have changed.\n> \n> \tI'm still putting my satellite station together and am down to picking\n> antenna's and feed line.\n> I am trying to build the station up for the future HEO birds as well,\n> so\n> what kind of overall db\n> receiving level should I be shooting for?\n> \n> \tHas anyone used \"Gulf Alpha\" antenna's? The cross polarized antenna's\n> look\n> very good to me. It wouldn't\n> be circular polarization but I would be able to switch between vertical\n> or\n> horizontal with a flip\n> of the switch.\n> \n> All help appreciated,\n> TNX\n> 73's\n> RoD\n> KD0XX\n\nRod:\n\nYour questions are numerous enough that I'm of the impression you would \nenjoy general introductions. I've found that the books offered by Amsat, as\nwell as the ARRL's _Radio Amateur's Satellite Handbook_ are excellent\nstarting points.\n\nThe AMSAT webstore has its publications at\nhttp://www.amsat-na.com/category.php?c=Publications\nI own _Getting Started_ (you'll want the 2006 edition), and I suspect\nyou'll like the _Digital Satellite and Telemetry Guide_, too. Because AO-51\nis a super test-bed for all this stuff, I'd recommend the book on it. If\nyou want the latest on what's happening, get the Proceedings of the 2006\nsymposium. And if you haven't become a member yet, please do.\n\nWhile there are other more expert than I on the subjects addressed above,\nI'll take a stab at answering them briefly. For digital modes, you can\ndemodulate with a computer soundcard and appropriate software very easily\nat 1200 bps rate; the 9600 bps rate (short-form, 9k6) is more difficult to\ndo in software, partly because your average soundcard link box for, say\npsk32, will likely use devices that limit the audio so that the signal\ncannot be demodulated. Apparently nobody has yet written software that can\ndemodulate 38600 bps (or 38k6).  If you're using a TS-2000 as your rig,\nthere is more specific advice I'd be happy to give. So the need of a TNC is\ndetermined by what birds you aim to communicate with, and how.\n\nModulation schemes, alas, vary in satellite work, but you can do quite a\nbit with the FM modulation you might be familiar with from terrestrial\npacket, which I believe is designated AFSK.\n\nIf you're aiming for antennas that will work on future HEO's, such as P3E,\nI would look around the web for descriptions of systems that worked well on\nAO-13 and AO-10. My impression from such research is that you really will\nwant fully circularly polarized antennas when that day comes, especially on\nmode B downlink: it's 3 dB that would take a lot of boom length to buy\notherwise. Back in the day, it seems, people used 7 - 10 element circ.\npolarized antennas. Of course, it depends on how far the bird is: I just\nwas playing around with the preliminary keps for P3E, and noticed that the\ndistance can be as far as almost 50,000 km away, but much fun can be had at\ndistances under 20,000 km. Plug that into the formulas in the books\ndescribed above, and you have the makings of a wonderful night of system\ndesign!\n\nYou ask about a commercial antenna design. Might I recommend getting your\nfeet wet in satellite work first with very cheap home-made antennas, say\nfive elements on 145 MHz and eight on 435 MHz? I've had a blast with such\nunits on the LEOs. They require far less precise aiming (you can do away\nwith the elevation rotor), and are well-equipped for the job.  They'll let\nyou find the kinks in your system. You're also less likely to QRO the bird\nwith such antennas. If you want to follow this way of thinking, there are\nmany of us who can lead you to some dead-simple antenna designs that use\nHome Depot parts.\n\nEither way you go, I note that you don't mention preamps. They are crucial.\n My strong recommendation is that you buy a mast-mounted SSBUSA or ARR\nbrand preamp for each band that you plan to receive on. I think you'll have\nmore fun with one of these hooked up to a vertical, than with a 20 element\ncirc. polarized yagi that has no preamp. \n\nFinally, if you're thinking ahead to the launch of P3E, don't forget S-band. \n\n73, Bruce\nVE9QRP\n",
    "attachments": []
}