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{ "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/NNZNRMEQZTGPI6Z7IXXF7XWNYR3U7YE6/?format=api", "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api", "message_id": "[email protected]", "message_id_hash": "NNZNRMEQZTGPI6Z7IXXF7XWNYR3U7YE6", "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/NNZNRMEQZTGPI6Z7IXXF7XWNYR3U7YE6/?format=api", "sender": { "address": "N2OEQ (a) aceweb.com", "mailman_id": "e63b1ea442884559874553314efaac46", "emails": "https://mailman.amsat.org/hyperkitty/api/sender/e63b1ea442884559874553314efaac46/emails/?format=api" }, "sender_name": "Patrick McGrane", "subject": "[amsat-bb] Re: P3E transponder and launch", "date": "2007-03-25T16:39:50Z", "parent": null, "children": [ "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/FD3DTITVAFE446DSQAYUTENSLZFWEYZE/?format=api" ], "votes": { "likes": 0, "dislikes": 0, "status": "neutral" }, "content": "Hello robert- thank you for a very well written explanation of the SDX system. I understand it better now.\nI'm still of the opinion that the satellites should be kept as simple as possible to increase reliability and life but I also believe in democracy and it sounds like it works well here. I dont agree with your \"outdated\" label of the old technology. Then again, I dont buy a new car every 5 years. Oscar 7 is a good example of the ruggedness of the old technology.\nYou're a very good tech writer, thanks for taking the time to explain, pat n2oeq\n\n\n\n\n------- Original Message -------\n>From : Robert McGwier[mailto:[email protected]]\nSent : 3/24/2007 11:54:26 AM\nTo : [email protected]\nCc : [email protected]; [email protected]; [email protected]\nSubject : RE: [amsat-bb] Re: P3E transponder and launch\n\n Thanks to everyone for the comments, concerns, and thoughtful remarks.\n\nSDX is no magic bullet. It cannot perform any better than the analog \nhardware around it and our careful work on doing the mixed signal work \nand even more careful work to make sure it survives the rigors of \ntraveling through Van Allan radiation belts four times a day!\n\nThat said, it provides us with several things. The DESIGN of the SDX \nwill allow us to use a high dynamic range receiver in comparison to \nthose we have flown before and to actually realize the potential \npresented to us by this receiver.\n\nIf we have this high dynamic range receiver, we can use a much lower \nnoise floor and wider dynamic range transmitter to provide cleaner \nsignals. This will be evidenced, if we do it right, by us no longer \nhearing the noise floor of the transponder. Next, if we have \nsufficient DSP horse power, we will be able to mitigate PAVE PAWS pulses \nby doing pulse detection and subtraction. THIS IS A LINEAR OPERATION. \nIt will be much nicer than clipping. If the pulses get so large that we \nare clipping then all bets are off but with an 80 dB dynamic range \nreceiver, this will be much less likely to happen. Stephensen has done \na detailed analysis of this and this is available on Eaglepedia.\n\nNext we are designing in the ability to provide the most capable HELAPS \nwe have ever done. HELAPS is high efficiency linear amplification by \nparametric synthesis. Technical papers by Karl are on both the AMSAT \nand AMSAT-DL web sites. It is envelope elimination and restoration \namplification. It allows us to use very high efficiency nonlinear \namplifiers in the transmit chain and then have the \"envelope\" of the \nhard limited signals from the transponder imposed on the signal just \nbefore it hits the antenna by modulating the voltage on the last or last \nfew stages. If we do the final transistors and the driver, we can get \nVERY high efficiency compared to what we have achieved in the past \nWITHOUT all of the poor IMD we lived with to get the efficiency. SDX is \n THE enabler in this.\n\nSDX provides us with the ability to easily find all alligators and \nimpose our will on them. There will simply be no benefit to running an \nEIRP that is larger than we decide to allow because YOUR INDIVIDUAL \nsignal will be suppressed!\n\n\nJuan Rivera, WA6HTP, and his team are building the fancy receiver which \nhas been designed by KD6OZH and peer reviewed to death by others. Parts \nare being purchased NOW and the goal is to have four soon. We are \nbuilding at least one to fit the P3E box shape.\n\nMarc Franco, N2UO, has designed, using modern parts that are very \ndifficult to get without connections, a serious 2 meter final stage. \nIt will provide the highest efficiency 2 meter transmitter we have ever \nflown for HELAPS.\n\nSteve Hendricksen, a TCNJ engineering student, design a S band \namplifier in a senior engineering project directed study for Marc, Al \nKatz (K2UYH), and I. He submitted this for competition in an amplifier \nefficiency contest. He received an honorable mention and came in very \nhigh in the rankings. However, his amplifier was the only one well in \nexcess of the minimum power, at 2.4 GHz rather than 1.0 GHz (the \ncontest minimum).\n\n\nAs always there is the balance between \"new with great promise but \nuntried\" and \"the old, standard but somewhat outdated\". We can have \nthis argument all year and it will never be easily resolved.\n\nAMSAT-UK has agreed to provide SDX software working with P3E and Eagle \nteams. They have agreed to copy the AO-13 RF if none of these fancier \nelements shows up and works. AMSAT-DL is planning for these contingencies.\n\nSo we have arranged for a small trial: Suisat-2 will carry a low power \nSDX with a few of these capabilities. We are planning a very large \nAMSAT engineering activity for this coming summer which you will hear \nmore about in the coming weeks.\n\n\nI could go on but what I want to promise is this: I have been extremely \nbusy both professionally, personally, and with AMSAT things and I have \nnot done an Engineering Notebook in a while. I will do a detailed paper \non this for the next journal and it will be in my engineering notebook. \n Following publication I will put the document with more backing \nmaterial on Eaglepeda as well and give it to AMSAT-DL for both our sites.\n\nBob\nN4H\n\n\nTony Langdon wrote:\n> At 10:46 AM 3/24/2007, John Champa wrote:\n>> Guys,\n>>\n>> The reports I have seen is that the SDX sounded BETTER than the\n>> traditional analog transponder. Bob, N4HY, can confirm that fact?\n> \n> I wouldn't be surprised at this one at all.\n> \n>> Anything other than SDX would be a step-backward for AMSAT.\n> \n> That's my viewpoint as well.\n> \n> 73 de VK3JED\n> http://vkradio.com \n> \n> \n\n-- \nAMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL,\nTAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair\n\"Taking fun as simply fun and earnestness in earnest shows\nhow thoroughly thou none of the two discernest.\" - Piet Hine\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", "attachments": [] }