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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/B5K3JKQZYHSDXJSNFPTUXBSAGVUNBMCS/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "B5K3JKQZYHSDXJSNFPTUXBSAGVUNBMCS",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/B5K3JKQZYHSDXJSNFPTUXBSAGVUNBMCS/?format=api",
    "sender": {
        "address": "AJ9N (a) aol.com",
        "mailman_id": "6748fe033a084371b465a1468321b4ea",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/6748fe033a084371b465a1468321b4ea/emails/?format=api"
    },
    "sender_name": "[email protected]",
    "subject": "[amsat-bb] Re: Help for Humber College Students with ISS Contact",
    "date": "2008-11-26T16:04:36Z",
    "parent": null,
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/PQYEL7AJEAH4HHNEKBBK7MLD7ISNTJWH/?format=api"
    ],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Hi all,\n \nLet me clear up a little bit of what ARISS wants for a school ground  \nstation.  What you do for your own home contact is your business but here  is what we \nwant for an ARISS school contact:\n \n1.  We require two complete radio stations, each one 75 watt  class or better \n(we actually prefer over 100).  RF amps are OK.  The  radios should have the \nability to go in frequency steps smaller than 5kHz so  that the Doppler shift \ncan be corrected (at 2 meters it goes about +/-3.5  kHz).\n2.  The primary radio is to have a circular polarized beam with  azimuth and \nelevation control rotors.  We prefer computer control of the  rotors.\n3.  The backup radio is to have a vertical and/or eggbeater style  antennas.\n \nNow for a short explanation of why for each:\n \n1.  The need for two complete radios is so that if one radio fails for  any \nreason, the school contact can carry on (it is recommended each radio be on  \nits own 120VAC circuit and UPS if possible).  The reason for the 75  watt class \nis that we want to have as much signal to reach the ISS as  possible.  The ISS \nis actually pretty noisy and the radio footprint is very  big and it picks up \nall sorts of interference.  So it helps to have as much  signal get to the \nastronaut.  Throw in the fact that the ISS superstructure  is so big now that we \nhave had schools have the signal dropout to almost nothing  and you can see \nthat every little bit helps.\n \n2.  The circular polarized beam helps because the signal to and from  the ISS \ncan be bouncing off of the superstructure itself and in some cases the  \nsurrounding ground terrain.  As I mentioned above, we have had some schools  where \nthe signal dropped out almost to zero.  Luckily the signal (sometimes  about a \nminute later) came back up as the ISS changed its orbital position  relative \nto the ground station and thus some of the blockage was reduced.   I have done \n4 school contacts as control op and I use 5x2  LHCP and 10x2 RHCP circular \npolarized beams with an antenna  switch.  Most of the ARISS telebridge stations \nare using something  similar.  The ISS antennas are basically vertical \nantennas but the signal  can be deflected all over the place because of the  \nsuperstructure.   I tend to run my contact on the RHCP beam (but  I am ready to \nswitch) but we at ARISS have had some reports where the signal did  come up a bit \nwhen using LHCP. Those who are really into satellite work know  that the RF \npattern does change during a contact so it makes sense to be able to  switch \npolarity.  And don't forget the ISS radio is running maybe 25 watts  (or maybe 5 \ndepending on the radio used) and can not do any Doppler  correction.\n \n3.  The backup radio is to have a non-directional antenna so that in  case of \nrotor or computer failure, the contact can carry on although it will be  with \na shortened contact time and the quality may suffer.  I have an  antenna \nswitch to switch between the 2 antennas during a pass as the RF pattern  between \nthe 2 antennas is completely different.\n \nThe biggest reason for doing what some may think is overkill is this.   The \nhams involved with a school contact are just the messengers.  The  school kids, \nteachers, and parents are the ones we have to satisfy and they  don't \nunderstand this ham radio business.  They do understand good audio  and no screw ups \non the part of the ham crew.  I always tell the schools  that I mentor to plan \non 600 to 800 people-hours for 10 minutes of contact  time.  They usually \nthink I am nuts until they do the contact and they  often tell me that my \nestimate was too low.  Think of a school contact as  your worst case Field Day; not \nso much because of the equipment issues but  because of the 600 or so kids \nwatching.\n \nHope this helps a little.\n \n73,\nCharlie Sufana AJ9N\nOne of the ARISS mentors\n \n \n \nIn a message dated 11/26/2008 4:15:52 A.M. Central Standard Time,  \[email protected] writes:\n\nKen 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 wondering if\n> I could ask for your  advice.  Well, you see, we've tested the transceiver\n> that we have  (the ICOM IC-V8000), and we can transmit and receive just fine\n> with it  on our circular-polarized HyGain 2m antenna.  Also, we did a  VSWR\n\nWhat kind of antenna?  Anything more than a 3-element Yagi  will be more \ntrouble than it's worth.  Bear in mind that I've  successfully sent and \nreceived APRS with the ISS using a homebrew  vertical.  The higher the \ngain of your Yagi, the more directional it  is, and the more accurately \nit needs to be pointed.  I find that a  3-element beam is okay for \nhandheld use when working portable, and has  more than enough gain to hit \nthe amateur satellites with 5W from an  HT.\n\n> test and our loss is minimal with the 75W transceiver that the  ICOM\n\n75W sounds a bit much, especially into a very directional antenna.  \nYou'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 ISS\n> produces.\n\nAre you using a 166MHz  aerial for this?  Are you sure the beacon is even \ntransmitting when  you think it is?  Your high gain Yagi might well be \nvery very deaf  outside its intended band.  Try making a simple dipole or \neven a  two-element beam for 166MHz.  With two elements, it will have a  \nmore-or-less cardioid pattern, so you shouldn't really even need to  \nsteer it much ;-)\n\n> My classmates and I are a bit  worried/stressed out.  I mean, just on last\n> Friday, we did a test  and someone drove at least 5km away from out college\n> and heard us fine  with the handheld radio he had.  We had a signal strength\n> of 3+  out of 5.  He could've drove out even further, but we felt that we  \ndid\n> enough testing to know that any attenuation losses were very  minimal.  \n\nThe ISS is pretty much the classic case of  line-of-sight.  There's \nnothing in the way, and it's only 200 miles  away.  There's nothing to \nstop the signal anywhere.\n\n> Well,  do you know what the problem could be?  Have you heard the  beacon?\n> What does it sound like?  Maybe we should delay or  advance the rotor by a\n> few seconds?   We're using NOVA  software, and it allows us to send our\n> transmission a few seconds  ahead or behind.  \n\nUse a wider beamwidth.\n\n> Ok, so we  have a circular polarized HyGain antenna hooked up to our Yaesu\n>  G5500.  Uhm, this might sound dumb but do you know whether we should  be\n> right hand circular polarized or left hand circular  polarized?  Is the ISS\n> right hand or left hand on  144.490MHz?  \n\nThis I'm not sure about.  I thought about  building a circular polarised \nantenna for ISS and amateur satellite work,  but it seemed more trouble \nthan it was worth.  If you've got the  polarisation wrong, it will be \nincredibly deaf!\n\n> I'm trying to  research this, but I'm having the hardest time to find this\n>  information out.  Oh, also, since our antenna is circular-polarized,  does\n> the way we set our antenna have an effect on our  transmission?  I know this\n> sounds confusing, but let me  explain:\n>  \n> If you looked at our antenna from the front so  that you could see all the\n> dipoles/elements both vertically and  horizontally to your view, well, \nshould\n> they be perfectly aligned with  one set horizontal and one vertical?  Both\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 are\n> more like an \"X\"  to your point of view (even though both are perfectly\n> 90degrees to  each other).\n\nThat shouldn't make much of a difference.  Imagine  the signal arriving \nlike a big corkscrew - the key to the circular  polarisation is that the \nsignal arrives at one set of elements and then a  quarter wavelength \nlater arrives at the second.  Now, let's imagine  we've made our \ncircular-polarised aerial by putting two dipoles on a boom,  1/4 \nwavelength apart, and connected them by two equal-length lines.   The \nvertical one is at the \"front\" of the boom and the horizontal one is  to \nthe \"back\", and the up and left elements of the dipoles are  \"hot\".\n\nLet's pause reality just as a \"vertical\" peak hits the vertical  dipole. \nThat dipole now has some signal.  Using the  single-Planck-time advance \nbutton on our Worldivo (it's like a Tivo for  the fundamental nature of \nthe Universe), we'll step through - tick, tick,  tick, tick - until a \nquarter wavelength has passed.  Now the vertical  peak is somewhere above \nthe centre of the horizontal dipole - it's picking  up no signal - and \nthere's a horizontal peak about the centre of the  vertical dipole - no \nsignal there either.\n\nStep forwards another  quarter wave, and there's a vertical dip at the \ncold end of the vertical  antenna, and the horizontal peak we just saw \ncame in is at the hot end on  the horizontal antenna.  We now have a \nnegative signal on the cold  side of the antenna connection (remember, \nboth dipoles are effectively in  parallel) and a positive signal on the \nhot side of the antenna connection  - loads of signal!\n\nIf 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 \ncompletely.  You can have two signals transmitted  in left and right \ncircular polarisation on the same frequency, and have  *phenomenal* \nrejection between the two.\n\nI should point out that  there's quite a lot in that explanation that's \nnot entirely true, or at  least terribly inaccurate.  It's still a useful \nmodel for getting  your head around what seems at first to be a very \nconfusing polarisation  mode.\n\nHTH,\nGordon\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\n**************Life should be easier. So should your homepage. Try the NEW \nAOL.com. \n(http://www.aol.com/?optin=new-dp&icid=aolcom40vanity&ncid=emlcntaolcom00000002)\n",
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