Email Detail
Show an email
GET /hyperkitty/api/list/[email protected]/email/QONVA6E7ZCE33UOQINGJUQT4DV5BUWDF/
{ "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/QONVA6E7ZCE33UOQINGJUQT4DV5BUWDF/", "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/", "message_id": "[email protected]", "message_id_hash": "QONVA6E7ZCE33UOQINGJUQT4DV5BUWDF", "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/AMZGDYJTDVRYUX2WF3QHR6TONUWEXQPV/", "sender": { "address": "wb4gcs (a) amsat.org", "mailman_id": "87014499e012476c8198fad186f7f963", "emails": "https://mailman.amsat.org/hyperkitty/api/sender/87014499e012476c8198fad186f7f963/emails/" }, "sender_name": "Jim Sanford", "subject": "[eagle] Re: [Fwd: [amsat-bb] Re: S band downlink on P3E]", "date": "2006-09-09T01:09:02Z", "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/QBIE4P4HVO2VOIYOEOS2UON4MPIV34AU/", "children": [], "votes": { "likes": 0, "dislikes": 0, "status": "neutral" }, "content": "Emily:\nGo look at the article on EaglePedia discussing the SD meeting.\n\nIn the appendix you will see spectrum analyzer plots.\n\nThanks & 73,\nJim\[email protected]\n\n\nEmily Clarke wrote:\n\n>I rarely post to this list but I hope you will accept my apologies \n>for doing so on this topic.\n>\n>At 05:31 PM 9/7/2006, Matt Ettus wrote:\n>\n> \n>\n>>I have a few problems with this.\n>>\n>>1 - It has bad selection bias. Amateurs who are already on satellites\n>>and who use S-band downlinks are the ones who don't have problems with\n>>interference. If they had interference, they wouldn't be on those\n>>bands.\n>> \n>>\n>\n>This is IMHO a very bad assumption. If this was a problem with AO-40 \n>or AO-51 (since the assumption is the problem grew expotentially \n>since 2003) then I think we would have heard volumes about it. We \n>haven't. I would be the first to defend that AO-51 is not the best \n>example to use, but I swept my yagi and downconverter around 360 \n>degrees with my spectrum analyzer attached. The spikes were s1 or \n>below. It's not a calibrated measurement, but I'd have to side with \n>the \"this isn't a problem\" folks. So I feel strongly more tests are needed.\n>\n> \n>\n>>Additionally, people currently on satellites tend to be those\n>>with lots of space for big dishes.\n>> \n>>\n>\n>I live in a townhouse - this is again a bad assumption. I work AO-51 \n>with a Yagi for 2.4G. If the wind conditions here in San Mateo are \n>light (which they generally aren't) I might put put up a 60CM dish, \n>but generally I won't. Even with the Yagi - WiFi is not a problem.\n>\n> \n>\n>> The point here is to open this up to\n>>people who won't, and would have more interference problems, since they\n>>live in denser areas and can't put up big dishes with lots of\n>>directional gain.\n>> \n>>\n>\n>San Mateo has almost a million people in a 12 mile radius. I get no \n>little inteference in the lower S band, and only a very small amount \n>of popping (that my DSP removes completely) in the upper S band. So \n>I personally need more convincing that this isn't a problem. At \n>worse we may have to convince our members to buy better \n>downconverters or add on notch filters so that their wideband \n>downconverters don't suck up noise from outside the band. But \n>telling people to get a filter isn't a big inconvenience. It's been \n>done before.\n>\n> \n>\n>>2 - Anecdotal \"evidence\" is pointless, especially since it is 5 years\n>>old. WiFi is a lot more popular now than it was 5 years ago.\n>> \n>>\n>\n>Matt, I don't want to seem confrontational, but so far all I've seen \n>is anecdotal eveidence from the Eagle team. I will admit I don't \n>read everything, but I do read things more closely when I see things \n>like camera shots from spectrum analyzers that are real \n>experiments. I haven't seen it.\n>\n>It is important to provide empirical data. I have a very open mind, \n>but so far the only thing I've seen are predictions of impending doom \n>and statistics, not hard data.\n>\n> \n>\n>>3 - Could you justify putting up an X million dollar satellite that uses\n>>a band which is questionable at best, just because some complainers who\n>>don't actually volunteer to do anything say that it works for them?\n>> \n>>\n>\n>I think this is a very good question - so if that is the argument, \n>why would you put up a mode U/V transponder? It's as usable as mud \n>in a gas tank.\n>\n> \n>\n>>4 - Why should we have to justify why we're not using a band?\n>> \n>>\n>\n>There are several reasons. The first is because we have spectrum \n>allocated there, and if we don't use it we simply lose it. In the \n>future we may need to rely upon it.\n>\n>The other reason is because the people who bought into the technology \n>5-10 years ago have an investment that hasn't yet been fully \n>realized. I don't want to go down the road questioning the judgement \n>of people who told our customer base to go down the road, but if it \n>was flawed we haven't told people we are sorry. It's also why none \n>of the commercial broadcasters cut off analog TV transmissions when \n>the FCC set the 2006 deadline. People hang on to technology.\n>\n> \n>\n>> As we\n>>agreed at the SD meeting, we are looking at providing _services_ and the\n>>best way to do that, not how to best make use of old hardware, which\n>>wouldn't be usable anyway.\n>> \n>>\n>\n>I wasn't invited to that meeting, but can you tell me why you don't \n>think it wouldn't be usable? I think that is a very bad assumption.\n>\n> \n>\n>>X-band is usable too. Why isn't anyone\n>>asking us to justify not using it?\n>> \n>>\n>\n>I'm not an expert at that level of microwave technology, but I think \n>that the biggest hurdle (and I could be slammed here) is that if we \n>were to try to launch an X-Band satellite I'm not sure the baseband \n>oscillator technology would be stable in space at a price we can \n>afford. Rick can comment on that - he's the GPS expert and I'm \n>commenting with only terrestrial experience. But putting a GPS \n>corrected clock for X-Band stabilization is something we haven't \n>tried before. However, perhaps we should, and I think the membership \n>would get behind that experiment.\n>\n>73,\n>\n>Emily\n>\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", "attachments": [ { "email": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/QONVA6E7ZCE33UOQINGJUQT4DV5BUWDF/", "counter": 2, "name": "attachment.html", "content_type": "text/html", "encoding": "us-ascii", "size": 6501, "download": "https://mailman.amsat.org/hyperkitty/list/[email protected]/message/QONVA6E7ZCE33UOQINGJUQT4DV5BUWDF/attachment/2/attachment.html" } ] }