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{ "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/CJSSQFG4TV4E5W7UJMYHGZQ5Q7ABJ7DL/?format=api", "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api", "message_id": "[email protected]", "message_id_hash": "CJSSQFG4TV4E5W7UJMYHGZQ5Q7ABJ7DL", "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/KK75DA42V2CVIKOT3KCXESRATCF6E3X2/?format=api", "sender": { "address": "w5did (a) amsat.org", "mailman_id": "8da25cae70294f3687f590ebe6fded03", "emails": "https://mailman.amsat.org/hyperkitty/api/sender/8da25cae70294f3687f590ebe6fded03/emails/?format=api" }, "sender_name": "Louis McFadin", "subject": "[eagle] Re: U-band receiver changes to reduce EMI and improve\tthermal regulation", "date": "2007-06-30T21:18:12Z", "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/NTVCX3OICHWZT7JSM42OOCHUATQDMPZR/?format=api", "children": [ "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/RJEZXVGCQGJBOI7JBSC3CES6TP7LXBSD/?format=api" ], "votes": { "likes": 0, "dislikes": 0, "status": "neutral" }, "content": "For a look at what is planned for the Eagle Power system, look at the \npresentation I prepared for Dayton this year. You can see it at \n\"http://homepage.mac.com/w5did\" Look in the w5did Eagle folder. The \nMax Solar Converter is a preliminary document annd not to be \npublished but it describes the converter very well.\n\n\nLou McFadin\nW5DID\[email protected]\n\n\nOn Jun 30, 2007, at 7:05 AM, Juan Rivera wrote:\n\n> John,\n>\n>\n>\n> For this particular application I think that approach might work, \n> but it forces others to make major concessions in terms of \n> utilization of space inside the enclosure to avoid CAN-Do radiated \n> EMI. Regardless of what happens to the CAN-Do EMI it looks like \n> you better plan on some nasty DC power and filter the DC input \n> accordingly.\n>\n>\n>\n> I can see a small PCB attached to the CAN-Do 40-pin connector that \n> contains DC filtering, the receiver’s switching power supply, and \n> lands for the signal lines that need to go back to the receiver \n> (not all 40 conductors – just the ones we actually use.) We’d \n> probably want to run those wires through to the other compartment \n> via feed-thru filters in the common bulkhead using a small wiring \n> harness, then another small harness on the other side to interface \n> to the receiver PCB. An alternate approach might be to use a \n> smaller ribbon cable and connectors to move the actual signals and \n> power back to the receiver, but that adds weight and doesn’t allow \n> for filtering through the bulkhead unless we found an EMI ribbon \n> cable bulkhead connector. I think I’d prefer the discrete wire \n> harness approach. I think it’s lighter, more reliable, and \n> eliminates one set of connectors.\n>\n>\n>\n> Before proceeding with another revision I’d like to see an EMI \n> requirement spec and a practical way to generate the expected noisy \n> DC power. This will also give the next group something to design \n> and test to.\n>\n>\n>\n> By the way, did you see my phase noise data? I went back and \n> tested again using another spectrum analyzer while mine is getting \n> calibrated. You’ll notice an interesting diversion between the \n> two. As the saying goes, “A man with a watch always knows what \n> time it is. A man with two watches can never be sure.” I’ll run \n> that again when I get the calibrated spec. a. back from the shop.\n>\n>\n>\n> 73,\n>\n> Juan\n>\n>\n>\n> From: John B. Stephensen [mailto:[email protected]]\n> Sent: Friday, June 29, 2007 10:38 PM\n> To: [email protected]; 'Louis McFadin'\n> Cc: 'Dave Black (Work)'; 'Dave Black (Home)'; 'David Smith'; \n> [email protected]; 'Samsonoff@Mac. Com'; 'Juan.Rivera (Work)'\n> Subject: Re: U-band receiver changes to reduce EMI and improve \n> thermal regulation\n>\n>\n>\n> If the CAN-Do module can be placed in a shielded compartment with \n> multi-pole filters on all wires leaving the shielded area, we can \n> get at least 80 dB of attenuation for conducted interference and \n> the electric field component of radiated interference. Magnetic \n> shielding is harder as it requires iron or mu-metal so a \n> magnetically shielded inductor should be used in the CAN-DO module.\n>\n>\n>\n> Synchronizing the switchers to a frequency with no harmonics at \n> 10.5-10.9 MHz would help with radiated interference, but a shielded \n> inductor may be sufficient if it can be moved far enough from the \n> RF circuitry -- especially the PLLS and VCOs.\n>\n>\n>\n> If we have only two adjacent sides available for connectors, the \n> CAN-Do module and power supply circuitry could attach to the \n> existing connector bracket. The RF and IF connectors would then \n> exit along one long side of the box as far from the CAN bus \n> connector as possible.\n>\n>\n>\n> 73,\n>\n>\n>\n> John\n>\n> KD6OZH\n>\n> ----- Original Message -----\n>\n> From: Juan Rivera\n>\n> To: 'John B. Stephensen' ; 'Louis McFadin'\n>\n> Cc: 'Dave Black (Work)' ; 'Dave Black (Home)' ; 'David Smith' ; \n> [email protected] ; 'Samsonoff@Mac. Com' ; 'Juan.Rivera (Work)'\n>\n> Sent: Saturday, June 30, 2007 04:32 UTC\n>\n> Subject: RE: U-band receiver changes to reduce EMI and improve \n> thermal regulation\n>\n>\n>\n> Hi John,\n>\n>\n>\n> I had a chat or two with Bob Davis about chassis and I think you \n> can bring SMA connectors out one side and the CAN-Do out the end, \n> but nothing out the back.\n>\n>\n>\n> Given the amount of conducted 5 kHz noise I’m seeing, do you think \n> you can filter it out? Don’t forget, I’m feeding the receiver with \n> bypassed clean DC from the bench supply at the moment. The CAN-Do \n> switched DC is nasty.\n>\n>\n>\n> In your next version why not raise the switching frequency up and \n> get it out of the passband completely? What do you think of \n> Howard’s idea of synching the switching supplies?\n>\n>\n>\n> Juan\n>\n>\n>\n> From: John B. Stephensen [mailto:[email protected]]\n> Sent: Friday, June 29, 2007 9:24 PM\n> To: Louis McFadin; [email protected]\n> Cc: Dave Black (Work); Dave Black (Home); David Smith; \n> [email protected]; Samsonoff@Mac. Com; Juan.Rivera (Work)\n> Subject: U-band receiver changes to reduce EMI and improve thermal \n> regulation\n>\n>\n>\n> For the next version of the 70 cm receiver, I'm thinking of an \n> arrangement where the CAN bus exits out of the opposite side of the \n> module from the RF and IF. Does this create any problems in the \n> wiring harness?\n>\n>\n>\n> The CAN-DO module would be mounted on a small PCB containing most \n> of the power supply circuitry. This PCB would contain the switcher \n> that generates 7 VDC for the receiver and some of the linear \n> regulators. It would be mounted at one end of the module and be \n> heat-sinked.\n>\n>\n>\n> The RF circuitry would be mounted on a separate PCB at the other \n> end of the module. This allows all RF and IF coax connectors to \n> mount on this PCB and attach directly to the connector mounting \n> bracket. It also eliminates the flying lead for the frequency \n> reference input. The power dissipation would be limited so that it \n> doesn't need to be heat-sinked. This protects the SAW filters from \n> rapid temperature excursions and keeps them above -30 C at all times.\n>\n>\n>\n> The two PCBs would be connected with a cable carrying DC power and \n> the signals being monitored. Each PCB would have filtering for \n> power and the signals being monitored by the IHU. The interconnect \n> cable would travel through a common-mode choke using high- \n> permiability ferrite.\n>\n>\n>\n> If necessary for thermal reasons, the RF amplifier and first mixer \n> would go on a third PCB with a heat sink. LO and IF would connect \n> to the second PCB via 2 coax cables. Once the new requirements \n> document is approved, the power dissipation can be calculated for \n> each of the 3 PCBs and a thermal analysis would determine whether 2 \n> or 3 PCBs are needed and how far apart they should be.\n>\n>\n>\n> Unless more problems are found during testing of the current \n> version of the receiver, the circuitry would be same as now, except \n> that an MCU is added to initialize the PLLs and the second mixer \n> and second IF amplifiers are changed to devices that dissipate less \n> power in line with the new requirements document. Bob has expressed \n> some interest in Peregrine PLLs that can have the frequency hard \n> wired so they could be inserted instead of adding the MCU.\n>\n>\n>\n> 73,\n>\n>\n>\n> John\n>\n> KD6OZH\n>\n> ----- Original Message -----\n>\n> From: Louis McFadin\n>\n> To: [email protected]\n>\n> Cc: Dave Black (Work) ; Dave Black (Home) ; David Smith ; \n> [email protected] ; Samsonoff@Mac. Com ; Juan.Rivera (Work)\n>\n> Sent: Saturday, June 30, 2007 02:36 UTC\n>\n> Subject: [eagle] Re: CAN-Do EMI - Let's Get Going on This!\n>\n>\n>\n> Juan,\n>\n> Why not think out of the box, Put the Can Do module outside the \n> box, perhaps on top of the module.\n>\n> I think that is a more likely solution than re building the Can-do \n> module.\n>\n>\n>\n> Lou McFadin\n> W5DID\n> [email protected]\n>\n>\n>\n>\n> On Jun 29, 2007, at 10:25 PM, Juan Rivera wrote:\n>\n>\n>\n> Bdale,\n>\n>\n>\n> I'm sorry to pick on you, but you seem like a good guy to complain \n> to...\n>\n>\n>\n> I seem to be having a problem stimulating a discussion. After \n> saying that I\n>\n> though the CAN-Do power supply needed to be completely scrapped and \n> replaced\n>\n> with one running at around 1 MHz I expected to be buried in email, \n> but I've\n>\n> only received one message referring to this so far, and it wasn't from\n>\n> anyone working on CAN-Do.\n>\n>\n>\n> The CAN-Do module is unique in that it is going to be an integral \n> component\n>\n> INSIDE of every payload, so any deficiencies it may have are going \n> to have a\n>\n> large impact.\n>\n>\n>\n> Let me restate my finding so far:\n>\n>\n>\n> There are 4 categories of EMI and the CAN-Do module / 70 cm Receiver\n>\n> combination is experiencing all four. They break down into \n> radiated and\n>\n> conducted emissions and susceptibility, and they are generally \n> referred to\n>\n> by a two-letter designation - RE, RS, CE, and CS.\n>\n>\n>\n> RE and RS go together - the CAN-Do module's switching power supply \n> inductor\n>\n> radiates the 5 kHz switching noise out the back directly towards the\n>\n> receiver (RE.) The Receiver's VCO's are both very sensitive to EMI \n> and are\n>\n> impacted by the CAN-Do module if they are within 4-1/2 inches of the\n>\n> inductor (RS.) I've had to move the CAN-Do module off of the \n> receiver PCB\n>\n> and interconnect it with a ribbon cable to deal with this problem. \n> The good\n>\n> news is that I am fairly confident that It can be fixed by going to a\n>\n> two-compartment chassis, with a bulkhead separating the CAN-Do \n> module from\n>\n> the analog Receiver to provide shielding. The bad news is that I \n> think this\n>\n> means we need a milled module chassis.\n>\n>\n>\n> CE and CS also go together, and this is the real problem I see \n> since you\n>\n> can't fix conducted EMI with a shielded enclosure. It requires \n> filtering.\n>\n> The CAN-Do module is trashing the DC input from the power source \n> and also\n>\n> feeding noisy power to the Receiver. The outgoing noise is the bigger\n>\n> concern because it will add to the CS problems for everything \n> connected to\n>\n> the power source. In the other direction, the switched power from the\n>\n> CAN-Do module shows up in the IF output as 5 kHz spurs. Moving the \n> CAN-Do\n>\n> module physically away from the Receiver only dealt with the RE/RS \n> issue. I\n>\n> had to bypass the CAN-Do module and run clean power directly from \n> the lab\n>\n> bench supply to deal with the CE/CS problem. This means that there \n> is no\n>\n> current monitoring and no power control.\n>\n>\n>\n> The 5 kHz switching frequency is bad for two reasons - it makes \n> filtering\n>\n> this noise a much larger problem than it needs to be, and the \n> impact is more\n>\n> severe since it is putting spurs all over the passband of the IF at \n> 5 kHz\n>\n> intervals.\n>\n>\n>\n> If you sit back and think about the impact of a dozen noisy power \n> supplies\n>\n> all feeding EMI back to the common power source where they all mix \n> together\n>\n> and make their way back to each payload, it starts to look nasty. \n> All these\n>\n> supplies will be drifting around and beating with each other to \n> produce sum\n>\n> and difference noise on the power bus. 5 kHz noise is hard enough \n> to get\n>\n> rid of but what if there are difference components at a few hundred \n> Hz? How\n>\n> can you design a filter when you won't know what to expect until \n> you hook\n>\n> everything up and turn it on? And by then you're out of time.\n>\n>\n>\n> I'm not making this stuff up. People I know have run into this exact\n>\n> problem before and the result was very bad.\n>\n>\n>\n> A while ago Howard Long made a suggestion that I think has great \n> potential.\n>\n> Here's what he had to say:\n>\n>\n>\n> ...in the original SDX PSU design I had in San Francisco last year \n> is an\n>\n> SMPS using the LM2672 device. These can be fitted with an AC \n> coupled SYNC\n>\n> signal to override the internal default SMPS frequency. I selected \n> 375kHz\n>\n> for my unit (6MHz divided by 16) to ensure its harmonics were \n> outside the\n>\n> 10.7MHz IF passband. If the external SYNC fails the internal SMPS \n> oscillator\n>\n> takes over.\n>\n>\n>\n> My Suggestions:\n>\n>\n>\n> 1) Revise the CAN-Do module to move the switching frequency up as \n> far as\n>\n> possible to move spurs out of the passband of sensitive analog \n> circuitry,\n>\n> and to ease the burden on EMI filtering.\n>\n> 2) The power and grounds must be filtered in both directions to \n> minimize CE\n>\n> back to the power source and to the payload.\n>\n> 3) The switching inductor should be a shielded to reduce RE inside the\n>\n> module chassis.\n>\n> 4) A power supply capable of synching to a master oscillator should be\n>\n> strongly considered.\n>\n>\n>\n> This topic needs to be elevated to the top of the queue. The EMI\n>\n> environment surrounding the CAN-Do module impacts the design of the \n> next\n>\n> revision of the 70 cm Receiver, and also directly impacts the chassis\n>\n> design. What do we need to do to get going on this?\n>\n>\n>\n> 73,\n>\n>\n>\n> Juan - WA6HTP\n>\n>\n>\n>\n>\n>\n>\n>\n>\n>\n>\n> _______________________________________________\n>\n> Via the Eagle mailing list courtesy of AMSAT-NA\n>\n> [email protected]\n>\n> http://amsat.org/mailman/listinfo/eagle\n>\n>\n>\n> _______________________________________________\n> Via the Eagle mailing list courtesy of AMSAT-NA\n> [email protected]\n> http://amsat.org/mailman/listinfo/eagle\n>\n>\n\n\n\n", "attachments": [ { "email": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/CJSSQFG4TV4E5W7UJMYHGZQ5Q7ABJ7DL/?format=api", "counter": 2, "name": "attachment.html", "content_type": "text/html", "encoding": "windows-1252", "size": 97793, "download": "https://mailman.amsat.org/hyperkitty/list/[email protected]/message/CJSSQFG4TV4E5W7UJMYHGZQ5Q7ABJ7DL/attachment/2/attachment.html" } ] }