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{ "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/PQYEL7AJEAH4HHNEKBBK7MLD7ISNTJWH/?format=api", "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api", "message_id": "001701c95020$09088a60$0200a8c0@Tanguray", "message_id_hash": "PQYEL7AJEAH4HHNEKBBK7MLD7ISNTJWH", "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/B5K3JKQZYHSDXJSNFPTUXBSAGVUNBMCS/?format=api", "sender": { "address": "rogerkola (a) aol.com", "mailman_id": "8323dbe496014835b5bd2be9b5ff6f66", "emails": "https://mailman.amsat.org/hyperkitty/api/sender/8323dbe496014835b5bd2be9b5ff6f66/emails/?format=api" }, "sender_name": "Roger Kolakowski", "subject": "[amsat-bb] Re: Help for Humber College Students with ISS Contact", "date": "2008-11-26T23:38:06Z", "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/B5K3JKQZYHSDXJSNFPTUXBSAGVUNBMCS/?format=api", "children": [ "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/7GSQEQUOKQZG25V3YJ55AVLY4LUWNVSO/?format=api", "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/RCU6I7JYOWV3VKO2WDNI227JFMN5RZNN/?format=api" ], "votes": { "likes": 0, "dislikes": 0, "status": "neutral" }, "content": "Nice 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 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 have\nthe\n> ability to go in frequency steps smaller than 5kHz so that the 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 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 be\non\n> its own 120VAC circuit and UPS if possible). The reason for the 75 watt\nclass\n> is that we want to have as much signal to reach the ISS as possible. The\nISS\n> is actually pretty noisy and the radio footprint is very big and it picks\nup\n> all sorts of interference. So it helps to have as much signal get to the\n> astronaut. Throw in the fact that the ISS superstructure is so big now\nthat we\n> have had schools have the signal dropout to almost nothing and you can\nsee\n> that every little bit helps.\n>\n> 2. The circular polarized beam helps because the signal to and from 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 circular\n> polarized beams with an antenna switch. Most of the ARISS 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 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 come\nup a bit\n> when using LHCP. Those who are really into satellite work know that 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 (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 case\nof\n> rotor or computer failure, the contact can carry on although it will be\nwith\n> a shortened contact time and the quality may suffer. I have an antenna\n> switch to switch between the 2 antennas during a pass as the 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 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 and no\nscrew ups\n> on the part of the ham crew. I always tell the schools that I mentor to\nplan\n> on 600 to 800 people-hours for 10 minutes of contact time. They usually\n> think I am nuts until they do the contact and they often tell me that my\n> estimate was too low. Think of a school contact as your worst case Field\nDay; not\n> so much because of the equipment issues but because of the 600 or so kids\n> 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 just\nfine\n> > with it on our circular-polarized HyGain 2m antenna. Also, we did a\nVSWR\n>\n> What kind of antenna? Anything more than a 3-element Yagi will be more\n> trouble than it's worth. Bear in mind that I've successfully sent and\n> received APRS with the ISS using a homebrew vertical. The higher the\n> gain of your Yagi, the more directional it is, and the more accurately\n> it needs to be pointed. I find that a 3-element beam is okay for\n> handheld use when working portable, and has more than enough gain to hit\n> 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 testing\n> > done, we still can't seem to pick up or hear the 166MHz beacon that the\nISS\n> > produces.\n>\n> Are you using a 166MHz aerial for this? Are you sure the beacon is even\n> transmitting when you think it is? Your high gain Yagi might well be\n> very very deaf outside its intended band. Try making a simple dipole or\n> even a two-element beam for 166MHz. With two elements, it will have a\n> more-or-less cardioid pattern, so you shouldn't really even need to\n> steer it much ;-)\n>\n> > My classmates and I are a bit worried/stressed out. I mean, just 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 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 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 should\nbe\n> > right hand circular polarized or left hand circular polarized? Is 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 polarised\n> antenna for ISS and amateur satellite work, but it seemed more trouble\n> than it was worth. If you've got the polarisation wrong, it will be\n> incredibly deaf!\n>\n> > I'm trying to research this, but I'm having the hardest time to find\nthis\n> > information out. Oh, also, since our antenna is circular-polarized,\ndoes\n> > the way we set our antenna have an effect on our transmission? I 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 all\nthe\n> > dipoles/elements both vertically and horizontally to your view, 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 other,\n> > however, instead of being a perfect cross to your view, the elements\nare\n> > more like an \"X\" to your point of view (even though both are perfectly\n> > 90degrees to each other).\n>\n> That shouldn't make much of a difference. Imagine the signal arriving\n> like a big corkscrew - the key to the circular polarisation is that the\n> signal arrives at one set of elements and then a quarter wavelength\n> later arrives at the second. Now, let's imagine we've made our\n> 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 to\n> 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 advance\n> button on our Worldivo (it's like a Tivo for the fundamental nature of\n> the Universe), we'll step through - tick, tick, tick, tick - until a\n> quarter wavelength has passed. Now the vertical peak is somewhere above\n> the centre of the horizontal dipole - it's picking up no signal - and\n> there's a horizontal peak about the centre of the vertical dipole - no\n> 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 the\n> hot side of the antenna connection - loads of signal!\n>\n> If we reversed the direction of the corkscrew, or reversed the phase 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 that's\n> not entirely true, or at least terribly inaccurate. It's still a useful\n> model for getting your head around what seems at first to be a very\n> 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 NEW\n> 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", "attachments": [] }