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    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/IE3TOMSY6MUSB327BYBGKWY546FVOW3K/",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/",
    "message_id": "000901c7c8f0$ed656560$0301a8c0@Shop",
    "message_id_hash": "IE3TOMSY6MUSB327BYBGKWY546FVOW3K",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/RQX4DLDIYY3MVVVNFRFO357N5UXLTUIQ/",
    "sender": {
        "address": "juan-rivera (a) sbcglobal.net",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "Juan Rivera",
    "subject": "[eagle] Re: Jim's comments",
    "date": "2007-07-18T04:05:48Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/3H2FYXIWU6IA2OXMEVBKQW2MRK2RHPOS/",
    "children": [
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/D5JYPAAXBN5PMM246M2EFOTB5ZH3N6AN/",
        "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/X6ABPZ7CIUAPAPYAEKSI5Z6I2IKPMPE4/"
    ],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
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    "content": "Jim and gang,\n\n \n\nI have a bit of new information for you regarding the CAN-Do step-down\nconverter:\n\n \n\nThe Maxim 1836 step-down converter is designed to deliver output currents of\nup to 125 milliamps, but in this circuit it is only supplying 11 mills.  The\nspec sheet shows that the efficiency and the switching frequency both drop\noff badly at that low output current.  It's pretty clear that this IC is not\nthe ideal choice for this very small load.  I can think of several\nalternatives:\n\n \n\n1)       Replace the noisy switching downconverter with a linear regulator\nand remove all traces of generated EMI\n\n2)      Find another more suitable step-down converter and design a new\ncircuit and a new PCB\n\n3)      At least for the 70 cm Receiver, disconnect the CAN-Do step-down\nconverter and power the CAN-Do module from the +5 volt receiver supply. It\nshouldn't even notice another 11 mills.\n\n \n\nLet's assume for the moment that we end up with a two-compartment enclosure.\nWhat if we just disable the CAN-Do module's step-down converter and create a\nsmall PCB that would attach to the 40-pin header and be the home for the\npower supplies for whatever was in the other side of the enclosure - in this\ncase the receiver analog circuitry.  The CAN-Do module would get its power\nfrom that little board and so would the receiver.  In the case of this\nreceiver we could put all the power supplies on a PCB about the size of a\nlarge postage stamp.\n\n \n\nDon, KD6IRE amplifies on my idea and suggests that the digital compartment\nbe placed off to the side - just wide enough to allow the existing CAN-Do\nmodule to fit.  The main compartment would then be an 'L' shape, but with\naccess to the front panel.  All RF and IF I/O from the rear compartment\nwould come up the leg on the \"L\", with SMA connectors all located on one\nside of the CAN-Do D connector.\n\n \n\nAgain speaking only from the perspective of the 70 cm receiver, I think this\nwould require the least amount of redesign and result in a pretty clean\npassband.  The benefits would be:\n\n \n\n1)       No major modifications to the CAN-Do module required (same PCB and\nsame connector)\n\n2)      No connectors out the side or the top creating wiring headaches\n\n3)      No more 5 kHz radiated or conducted CAN-Do EMI inside the enclosure\nor propagated back up the DC power lines (5 kHz spurs completely gone)\n\n4)      Moves the 157 kHz receiver switching power supply to the separate\ncompartment in the front on that little daughter board and gets rid of that\nspur in the passband\n\n5)      Minor modifications to the enclosure - just another internal sheet\nmetal piece\n\n6)      The Receiver PCB form factor could remain the same or it could\nchange to the \"L\" shape, depending on what works best.\n\n \n\nThis still leaves the issue of flex unresolved and this suggestion might not\nwork for every project but it seems like it might be worth trying.\n\n \n\n73,\n\n \n\nJuan\n\n \n\nP.S.  Maxim 1836 link -->\nhttp://datasheets.maxim-ic.com/en/ds/MAX1836-MAX1837.pdf\n\n \n\n\n\n",
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