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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/ZMRGR3XMEA52BMY7G5OMET7KFSI5H5EU/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "ZMRGR3XMEA52BMY7G5OMET7KFSI5H5EU",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/ZMRGR3XMEA52BMY7G5OMET7KFSI5H5EU/?format=api",
    "sender": {
        "address": "K3IO (a) verizon.net",
        "mailman_id": "79a9b3ddaa4b44baae47f92374974ac4",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/79a9b3ddaa4b44baae47f92374974ac4/emails/?format=api"
    },
    "sender_name": "Tom Clark, K3IO",
    "subject": "[amsat-bb] Re: S band and Eagle: an appeal for a higher level\tdiscussion",
    "date": "2006-09-08T05:04:15Z",
    "parent": null,
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/GNVX4FPY5O4IEQSA4GGRST2EJMUXWUOV/?format=api",
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/OCY6ZJNXN2C642XW52FHD3RNKHXN5ZCS/?format=api"
    ],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "At the risk of bodily attack, let me offer some comments on the topic\nthat has produced so much AMSAT-BB traffic. The Eagle Mode-S decision\nwas made at the conclusion of an intense, but very productive design\nmeeting held in San Diego, just 2 months ago, at the end of June.\n\nIn case you feel that we haven't told you what went on and why the\nradical changes, please refer to the very latest (July/August) AMSAT\nJOURNAL for some of the details of the meeting. In particular, I ask you\nto read Rick's (W2GPS) editorial on Page 3, and Bob's (N4HY)\n\"Engineering Notebook\" beginning with \"Warning: Honesty Follows\" on\npages 9/10, and the Jim's (WB4GCS) Eagle Update on pages 24/25. Also,\nyou can glean some details of the meeting and its conclusions in the\nK3IO/N4HY presentation at the Central States VHF Society (CSVHFS)\nMeeting in July; that material is on my personal website at\nhttp://mysite.verizon.net/~w3iwi/EAGLE_CSVHFS.pdf\n<http://mysite.verizon.net/%7Ew3iwi/EAGLE_CSVHFS.pdf> (~3.9 MB in size)\nor in its full-blown (a huge 19MB in size) PowerPoint version as\nhttp://mysite.verizon.net/~w3iwi/EAGLE_CSVHFS.ppt\n<http://mysite.verizon.net/%7Ew3iwi/EAGLE_CSVHFS.ppt>.\n\nAs you can see from the pictures in Bob's Engineering Notebook, the\nmeeting included your AMSAT President (W2GPS), VP of Engineering (N4HY),\nEagle Project Manager (WB4GCS) and two Board members (W2GPS & K3IO). To\nanswer one oft-posed question, the entire Board has not met since the\nJune meeting; the material constitutes the current \"best guess\"\nengineering forecast, and the Board has been told of the conclusions\n(and they have read the Journal); but as of now no votes have been\ntaken. Feel free to contact the Board members if you feel that your\ndesires have not been taken into consideration. A full list appears on\nPage 3 of the Journal, and all can be reached by Email addressed to\[email protected].\n\nAfter the design group went through careful estimates of the link\nbudgets for each of the classes of users we considered (see Jim's paper\non Page 24 and/or my CSVHFS presentation), and considered the\nfeasibility of making the spacecraft work, we came to the conclusion\nthat my C-C Rider concept wouldn't fly; there was no way we could obtain\nenough T/R isolation for full-duplex operation, and using half-duplex\nwith the time delays associated with a satellite 40,000 km away was\nimpractical. C'est la vie.\n\nWe considered the RFI environment carefully (see my CSVHFS paper for\ndetails) as it would exist 10 years from now. Why 10 years? Well, it\nwill take us 3-4 years to fly Eagle, and then we hope it will last and\nbe useful for at least a decade, so a 10 year forecast seemed about\nright. In that time frame, many of us (me especially) feel that the\nEuropean Galileo GNSS (Global Navigation Satellite System, i.e. GPS)\n(and possibly similar systems being designed in Japan & China) will have\nprime DOWNLINK signals overlaying our 1260-1270 MHz UPLINK band. The\nsignals being sent down may well be deemed critical for \"Safety of Life\"\nservices; it is not unlikely (double negative used intentionally) that\nadministrations may cancel out our L-band uplink so those \"damned Hams\ncan't cause an A380 with 500 people on board to crash!\". Since weight,\npower and volunteer engineering talent are all finite resources, we came\nto the conclusion that it was not prudent for us to invest in an L-band\nuplink.  C'est la vie.\n\nWe  then considered the S1 (13 cm) and S2 (9 cm) allocations.  It's a\npity that amateurs cannot use the S2 = 9 cm (3400 MHz) band in Region 1;\nit would be PERFECT as an alternate to L-band. I argued long and hard\nfor it and was beaten down. However, it might find some use for\ntelemetry downlinks. The 10 GHz = X-band and higher microwave\nfrequencies were considered as possible interesting channels for\nexperimental use, but not really practical for \"heavy lifting\"\ntransponders. C'est la vie. I'll come back to S1 & C-band in a bit.\n\nDuring the discussions we put in hard numbers for each of the possible\nbands for each of the classes of users we envisioned (See Jim's article\non Page 23 and my slides). We were already planning on the use of a\nMode-B (70 cm up, 2M down) Software Defined Transponder (SDX) which\nwould be PERFECT for the legacy \"Class-0\" users. We then discussed our\ndesire for a new Class-1 service. This is envisioned as a service which\ncan send short text messages from portable hand-held terminals, rather\nlike the SMS messaging service in wide use by teen-agers and similar to\nBob Bruninga's APRS messaging. The idea is based in a desire to have\nAmateur Radio ready for the next Katrina or Christmas Tsunami disaster.\nWhen we put in the link budget numbers for hand-held terminals\n(including antennas) with a satellite at 40,000 km range, it also\ndictated the use of Mode-B. (Detailed spreadsheets justifying this\nconclusion are posted on EaglePedia). In fact, Fran Brickle (AB2KT) is\nalready hard at work on the protocol and SDX code and plans to present a\npaper at San Diego.\n\nNow let's turn our attention to the controversial S-band topic. Jan King\n(W3GEY/VK4GEY) presented quantitative results that he and Kerry Banke\n(N6IZW) had obtained in San Diego, Palo Alto & Queensland on the 2.4 GHz\nRFI environment. He indicated that, even in the midst of a field\nhundreds of meters from the nearest building, the RFI levels were 20+ dB\nabove thermal as seen with a non-directional antenna. Others in the\nmeeting reported anecdotal data that noise levels in some small towns\nhad increased 60+ dB in three years since WiFi systems were installed.\nSeveral people in the meeting told the effects of the newer (802.11G and\n802.11DraftN) 50-100 Mbit/s systems and discussed plans that they new\nindustry had in the pipeline that will make the situation even worse.\nThis is especially true on the 10+ year time scales that Eagle must be\ndesigned for. In my CSVHFS paper, you will see a slide that says \"S-Band\nis a Sewer\". Part of this is our own inadvertent fault. With AO-40 &\nAO-51, we use S-Band in a receive mode. The non-licensed users have no\nidea that we are occupying the frequency. What better way to clear them\nout (now here's a radical thought) than by TRANSMITTING instead of\nreceiving! And we noted the easy availability of surplus S-band power\namplifiers at the 5-30 watt level. Thus S-band lost its \"beauty\" for\ndownlink and became a band for uplinks. And we noted that in locations\nwhere a fairly high power ATV repeater was operating on S-band, the QRM\nwas a LOT less.\n\nYes, this decision was based on incomplete data. It would be wonderful\nif many of you took the challenge to make quantitative measurements of\nthe S-band RFI levels in multiple locations. Just take your S-band LNA,\nput on a low-gain antenna and measure the difference in background noise\nlevel between that antenna and a 50 ohm dummy load as accurately as you\ncan. You will get better accuracy if you can  use a wide measurement\nbandwidth (10-100 kHz or so). Remember to disable your receiver's AGC. A\ngood spectrum analyzer would be an excellent choice to use as the\ndetector. Please feel free to send me any such measurements along with\nnotes on the equipment you used and the environment where you made the\ntests (urban, rural, etc). My Email address is mailto:[email protected].\n\nSince L and S2 had been ruled out for reasons described above, this left\nus with the possibility of using C-band as a DOWNLINK. There are some\nconcerns about the 802.11A/cordless phone/etc QRM, but we noted that the\nAmateur Satellite DOWNLINK band is above most of the crap (5830-5850\nMHz). The work I had done on C-C Rider had shown that, with a phased\narray antenna and a power amplifier at each element, we could generate\nadequate power so that a Class-A user with a 50 cm diameter (i.e.\nDirecTV) dish would have good performance.\n\nThe S/C links were designed as digital links. The uplink signals would\nhave error correction coding that would be decoded at the spacecraft,\nand then sent down with \"fresh\" codes on the downlink. This makes the\nsatellite links much easier (by tens of dB) than if they were \"bent\npipe\" linear links. The users would be able to use any type of signal\nthey desire (Voice, SSTV or even CW). In all this design work, we took\ninto account that the typical user does not have the digital and S/C RF\nwidgets. The plan is to develop the user's hardware at the same time, in\nparallel with the spacecraft hardware; AMSAT would then make this\navailable to all. We envisioned using the TAPR TNC-2 model -- TAPR\n\"seeded\" the community by distributing a few hundred kits, and then\nlicensed the design to commercial manufacturers.\n\nIn conclusion, I ask you, the satellite users to consider what will be\nthe state-of-the-art and the state of amateur radio in the window 5-15\nyears from now. It may be painful to admit that you invested in an\nS-band down converted and barbecue grill dish for a now-defunct AO-40.\nJust consider the big picture -- I've been around long enough to think\nback on the early 70s: People had cobbled together 2M CW transmitters\nfor use on Mode-A with AO-6. Then AO-7 came along with Mode-B and the\nloud cry went up \"Now we have to throw away our 2M transmitters and then\nfigure out how to make a transmitter that can work on UHF!!\". And when\nthe lower frequency transmitters failed on AO-40, people had to listen\non S-band. Admit it -- it wasn't all that hard to accept new technology.\n\n73 de Tom, K3IO\n\n",
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