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GET /hyperkitty/api/list/[email protected]/email/7GSQEQUOKQZG25V3YJ55AVLY4LUWNVSO/?format=api
{ "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/7GSQEQUOKQZG25V3YJ55AVLY4LUWNVSO/?format=api", "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api", "message_id": "5C0D06C96B014D278A425293A13B2613@athlon", "message_id_hash": "7GSQEQUOKQZG25V3YJ55AVLY4LUWNVSO", "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/B5K3JKQZYHSDXJSNFPTUXBSAGVUNBMCS/?format=api", "sender": { "address": "ve4yz (a) mts.net", "mailman_id": null, "emails": null }, "sender_name": "Alan", "subject": "[amsat-bb] Re: Help for Humber College Students with ISS Contact", "date": "2008-11-27T02:16:27Z", "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/PQYEL7AJEAH4HHNEKBBK7MLD7ISNTJWH/?format=api", "children": [ "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/DWXAPPLBI4HITJ5UUZKIFFG5DN53SUNH/?format=api" ], "votes": { "likes": 0, "dislikes": 0, "status": "neutral" }, "content": "With all due respect to describing LHCP and RHCP which gives me a brain\ncrap... Here is a visualization of polarization.\n\nhttp://sv1bsx.50webs.com/antenna-pol/polarization.html\n\n\n... Alan\n\n\n-----Original Message-----\nFrom: [email protected] [mailto:[email protected]] On\nBehalf Of Roger Kolakowski\nSent: November 26, 2008 5:38 PM\nTo: [email protected]; [email protected]; [email protected];\[email protected]\nSubject: [amsat-bb] Re: Help for Humber College Students with ISS Contact\n\nNice explanation...Thank you!\n\nRoger\nWA1KAT\n\n----- Original Message -----\nFrom: <[email protected]>\nTo: <[email protected]>; <[email protected]>; <[email protected]>\nSent: Wednesday, November 26, 2008 11:04 AM\nSubject: [amsat-bb] Re: Help for Humber College Students with ISS Contact\n\n\n> Hi all,\n>\n> Let me clear up a little bit of what ARISS wants for a school ground \n> station. What you do for your own home contact is your business but \n> here\nis what we\n> want for an ARISS school contact:\n>\n> 1. We require two complete radio stations, each one 75 watt class or\nbetter\n> (we actually prefer over 100). RF amps are OK. The radios should \n> have\nthe\n> ability to go in frequency steps smaller than 5kHz so that the \n> Doppler\nshift\n> can be corrected (at 2 meters it goes about +/-3.5 kHz).\n> 2. The primary radio is to have a circular polarized beam with \n> azimuth\nand\n> elevation control rotors. We prefer computer control of the rotors.\n> 3. The backup radio is to have a vertical and/or eggbeater style\nantennas.\n>\n> Now for a short explanation of why for each:\n>\n> 1. The need for two complete radios is so that if one radio fails for\nany\n> reason, the school contact can carry on (it is recommended each radio \n> be\non\n> its own 120VAC circuit and UPS if possible). The reason for the 75 \n> watt\nclass\n> is that we want to have as much signal to reach the ISS as possible. \n> The\nISS\n> is actually pretty noisy and the radio footprint is very big and it \n> picks\nup\n> all sorts of interference. So it helps to have as much signal get to \n> the astronaut. Throw in the fact that the ISS superstructure is so \n> big now\nthat we\n> have had schools have the signal dropout to almost nothing and you \n> can\nsee\n> that every little bit helps.\n>\n> 2. The circular polarized beam helps because the signal to and from \n> the\nISS\n> can be bouncing off of the superstructure itself and in some cases the \n> surrounding ground terrain. As I mentioned above, we have had some\nschools where\n> the signal dropped out almost to zero. Luckily the signal (sometimes\nabout a\n> minute later) came back up as the ISS changed its orbital position\nrelative\n> to the ground station and thus some of the blockage was reduced. I have\ndone\n> 4 school contacts as control op and I use 5x2 LHCP and 10x2 RHCP \n> circular polarized beams with an antenna switch. Most of the ARISS \n> telebridge\nstations\n> are using something similar. The ISS antennas are basically vertical \n> antennas but the signal can be deflected all over the place because \n> of\nthe\n> superstructure. I tend to run my contact on the RHCP beam (but I am\nready to\n> switch) but we at ARISS have had some reports where the signal did \n> come\nup a bit\n> when using LHCP. Those who are really into satellite work know that \n> the\nRF\n> pattern does change during a contact so it makes sense to be able to\nswitch\n> polarity. And don't forget the ISS radio is running maybe 25 watts \n> (or\nmaybe 5\n> depending on the radio used) and can not do any Doppler correction.\n>\n> 3. The backup radio is to have a non-directional antenna so that in \n> case\nof\n> rotor or computer failure, the contact can carry on although it will \n> be\nwith\n> a shortened contact time and the quality may suffer. I have an \n> antenna switch to switch between the 2 antennas during a pass as the \n> RF pattern\nbetween\n> the 2 antennas is completely different.\n>\n> The biggest reason for doing what some may think is overkill is this.\nThe\n> hams involved with a school contact are just the messengers. The \n> school\nkids,\n> teachers, and parents are the ones we have to satisfy and they don't \n> understand this ham radio business. They do understand good audio \n> and no\nscrew ups\n> on the part of the ham crew. I always tell the schools that I mentor \n> to\nplan\n> on 600 to 800 people-hours for 10 minutes of contact time. They \n> usually think I am nuts until they do the contact and they often tell \n> me that my estimate was too low. Think of a school contact as your \n> worst case Field\nDay; not\n> so much because of the equipment issues but because of the 600 or so \n> kids watching.\n>\n> Hope this helps a little.\n>\n> 73,\n> Charlie Sufana AJ9N\n> One of the ARISS mentors\n>\n>\n>\n> In a message dated 11/26/2008 4:15:52 A.M. Central Standard Time, \n> [email protected] writes:\n>\n> Ken Owen wrote:\n> <snip>\n> > From: Paul Je [mailto:[email protected]]\n> > Sent: Monday, November 24, 2008 1:17 PM\n> > To: Ken Owen\n> > Subject: RE: ISS contact\n> >\n> > Say Ken, we've set up our primary station just fine, but I was\nwondering if\n> > I could ask for your advice. Well, you see, we've tested the\ntransceiver\n> > that we have (the ICOM IC-V8000), and we can transmit and receive \n> > just\nfine\n> > with it on our circular-polarized HyGain 2m antenna. Also, we did \n> > a\nVSWR\n>\n> What kind of antenna? Anything more than a 3-element Yagi will be \n> more trouble than it's worth. Bear in mind that I've successfully \n> sent and received APRS with the ISS using a homebrew vertical. The \n> higher the gain of your Yagi, the more directional it is, and the \n> more accurately it needs to be pointed. I find that a 3-element beam \n> is okay for handheld use when working portable, and has more than \n> enough gain to hit the amateur satellites with 5W from an HT.\n>\n> > test and our loss is minimal with the 75W transceiver that the ICOM\n>\n> 75W sounds a bit much, especially into a very directional antenna.\n> You're trying to talk to the ISS, not etch your name on the side.\n>\n> > produces. Ok, so here's the problem. Even with all the proper \n> > testing done, we still can't seem to pick up or hear the 166MHz \n> > beacon that the\nISS\n> > produces.\n>\n> Are you using a 166MHz aerial for this? Are you sure the beacon is \n> even transmitting when you think it is? Your high gain Yagi might \n> well be very very deaf outside its intended band. Try making a \n> simple dipole or even a two-element beam for 166MHz. With two \n> elements, it will have a more-or-less cardioid pattern, so you \n> shouldn't really even need to steer it much ;-)\n>\n> > My classmates and I are a bit worried/stressed out. I mean, just \n> > on\nlast\n> > Friday, we did a test and someone drove at least 5km away from out\ncollege\n> > and heard us fine with the handheld radio he had. We had a signal\nstrength\n> > of 3+ out of 5. He could've drove out even further, but we felt \n> > that\nwe\n> did\n> > enough testing to know that any attenuation losses were very minimal.\n>\n> The ISS is pretty much the classic case of line-of-sight. There's \n> nothing in the way, and it's only 200 miles away. There's nothing to \n> stop the signal anywhere.\n>\n> > Well, do you know what the problem could be? Have you heard the\nbeacon?\n> > What does it sound like? Maybe we should delay or advance the \n> > rotor by\na\n> > few seconds? We're using NOVA software, and it allows us to send our\n> > transmission a few seconds ahead or behind.\n>\n> Use a wider beamwidth.\n>\n> > Ok, so we have a circular polarized HyGain antenna hooked up to our\nYaesu\n> > G5500. Uhm, this might sound dumb but do you know whether we \n> > should\nbe\n> > right hand circular polarized or left hand circular polarized? Is \n> > the\nISS\n> > right hand or left hand on 144.490MHz?\n>\n> This I'm not sure about. I thought about building a circular \n> polarised antenna for ISS and amateur satellite work, but it seemed \n> more trouble than it was worth. If you've got the polarisation \n> wrong, it will be incredibly deaf!\n>\n> > I'm trying to research this, but I'm having the hardest time to \n> > find\nthis\n> > information out. Oh, also, since our antenna is \n> > circular-polarized,\ndoes\n> > the way we set our antenna have an effect on our transmission? I \n> > know\nthis\n> > sounds confusing, but let me explain:\n> >\n> > If you looked at our antenna from the front so that you could see \n> > all\nthe\n> > dipoles/elements both vertically and horizontally to your view, \n> > well,\n> should\n> > they be perfectly aligned with one set horizontal and one vertical?\nBoth\n> > the vertical and the horizontal are perfectly 90degrees to each \n> > other, however, instead of being a perfect cross to your view, the \n> > elements\nare\n> > more like an \"X\" to your point of view (even though both are \n> > perfectly 90degrees to each other).\n>\n> That shouldn't make much of a difference. Imagine the signal \n> arriving like a big corkscrew - the key to the circular polarisation \n> is that the signal arrives at one set of elements and then a quarter \n> wavelength later arrives at the second. Now, let's imagine we've \n> made our circular-polarised aerial by putting two dipoles on a boom, 1/4\n> wavelength apart, and connected them by two equal-length lines. The\n> vertical one is at the \"front\" of the boom and the horizontal one is \n> to the \"back\", and the up and left elements of the dipoles are \"hot\".\n>\n> Let's pause reality just as a \"vertical\" peak hits the vertical dipole.\n> That dipole now has some signal. Using the single-Planck-time \n> advance button on our Worldivo (it's like a Tivo for the fundamental \n> nature of the Universe), we'll step through - tick, tick, tick, tick \n> - until a quarter wavelength has passed. Now the vertical peak is \n> somewhere above the centre of the horizontal dipole - it's picking up \n> no signal - and there's a horizontal peak about the centre of the \n> vertical dipole - no signal there either.\n>\n> Step forwards another quarter wave, and there's a vertical dip at the \n> cold end of the vertical antenna, and the horizontal peak we just saw \n> came in is at the hot end on the horizontal antenna. We now have a \n> negative signal on the cold side of the antenna connection (remember, \n> both dipoles are effectively in parallel) and a positive signal on \n> the hot side of the antenna connection - loads of signal!\n>\n> If we reversed the direction of the corkscrew, or reversed the phase \n> of\n> *one* of the dipoles, then the two signals would cancel out almost \n> completely. You can have two signals transmitted in left and right \n> circular polarisation on the same frequency, and have *phenomenal* \n> rejection between the two.\n>\n> I should point out that there's quite a lot in that explanation \n> that's not entirely true, or at least terribly inaccurate. It's \n> still a useful model for getting your head around what seems at first \n> to be a very confusing polarisation mode.\n>\n> HTH,\n> Gordon\n> _______________________________________________\n> Sent via [email protected]. Opinions expressed are those of the author.\n> Not an AMSAT-NA member? Join now to support the amateur satellite\nprogram!\n> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb\n>\n>\n> **************Life should be easier. So should your homepage. Try the \n> NEW AOL.com.\n>\n(http://www.aol.com/?optin=new-dp&icid=aolcom40vanity&ncid=emlcntaolcom00000\n002)\n> _______________________________________________\n> Sent via [email protected]. Opinions expressed are those of the author.\n> Not an AMSAT-NA member? Join now to support the amateur satellite program!\n> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb\n>\n\n_______________________________________________\nSent via [email protected]. Opinions expressed are those of the author.\nNot an AMSAT-NA member? Join now to support the amateur satellite program!\nSubscription settings: http://amsat.org/mailman/listinfo/amsat-bb\n\n", "attachments": [] }