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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/UMWUD5XV7BM53DCEXBY5ZBNDH5THMLWY/",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/",
    "message_id": "[email protected]",
    "message_id_hash": "UMWUD5XV7BM53DCEXBY5ZBNDH5THMLWY",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/UMWUD5XV7BM53DCEXBY5ZBNDH5THMLWY/",
    "sender": {
        "address": "pa3fym (a) amsat.org",
        "mailman_id": "5f42a625d6474192905b3f519de084db",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/5f42a625d6474192905b3f519de084db/emails/"
    },
    "sender_name": "Remco",
    "subject": "[amsat-bb] EsHail Microwave transponder satellite",
    "date": "2016-06-02T10:05:13Z",
    "parent": null,
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Having posted my setup at the end of last month and\nseeing that my mail program wrapped line feeds, decreasing\nreadibility, here again my description and perspective.\n\n\nEs'hail2 will not differ from any other geostationary broadcast satellite\nin a sense that it's a 'full duplex' repeater with some time delay. \n\n\nI reckon this time delay inhibits actual full duplex operation,\njust like the TV reporter for a 'live stand up' in the TV news via\na satellite link having an earplug with all audio except himself ('N-1'). \n\n\nFor us amateurs this means no (significant) Doppler shift, \nno LSB/USB issues etc.\n\n\nJust point your dish once to 25.5E like (more than) thousands of \nbroadcast satellite viewers do (without technical knowledge at all ;-)\n\n\nDownlink (10.5 GHz):\nFor narrow band usage frequency and stability is paramount. \nFor 10.5 GHz we're helped by the BC satellite industry, offering\ncheap PLL LNB's with 'HDTV precision'.\n\n\nImho this precision needs to be increased by injection locking\nthe LNB PLL with e.g. a GPSDO due to the large multiplification\nfactor inside the LNB (e.g. for Octagon 361.111111).\n\n\nNoise figures (NF) of these LNB's are somewhat higher on 10.5 GHz \ndue to (steep) wave guide cut off, but still usable, compared to \nthe ease and price.\n\n\nUplink (2.4 GHz):\nA 10W BUC (block up converter) suffices with published specs of \nthe 2.4 GHz receiver above in conjunction with a ca. 75cm dish here.\n\n\nI'm currenly developing a simple 2.4 GHz BUC and will use old UMTS pallets\nto amplify the desired 2400 MHz output.\nPicture of my UMTS pallets: http://remco.org/umts.jpg\n\n\nBear in mind, S-band power is cheap :-)\n\n\nAntenna:\nOne dish, the larger the better. Not for the uplink, but for improving\ndynamic range at the receiver (downlink) side.\n\n\nI will use a surplus Triax 88cm dish (for portable / 'umbrella' use ;-),\nf/D is around 0.6 (like most consumer BC satellite dishes).\n\n\nFeed:\nFrom my perspective the only challenge lies in the 2.4 GHz uplink.\nThat is, to make an S-band feed which phase center coincides with the\n10.5 GHz LNB (which has its own 'feed' ;-)\n\n\nI've no fear for isolation issues due to the large frequency difference.\n\n\nI am told that circular polarisation (CP) is 'mandatory' for S-band\nuplinks in general but can't find a verification for this, \nperhaps somebody else?\n\n\nAnyway, we're amateurs and creative. So when RHCP uplink is too\ndifficult we make a linear antenna and increase uplink power with 3 dB ;-)\n\n\nBut, I follow the published receiver specifications . . .\nLast week I made a 6 turn LHCP 2.4 GHz helix. \n(Rule of thumb seems to be 1 turn per 0.1 f/D)\nPhase center of such a helix is a bit 'foggy' but from what I read lies\nsomewhere between the first and second turn.\n\n\nI've some issues with matching it due to some mechanical boundary conditions\nof the helix feed point in conjunction with the mounted downlink LNB and\nrelative position of the helix. \nThere is an additional 'transmission line' involved and \na 'normal' 1/4-wave stub doesn't give me the desired return loss.\nSo, this needs some fiddling, perhaps with a gamma match or so.\n\n\nMy approach is, the downlink LNB is mounted in the dish 'as usual' and\nlooks through the centre of the uplink helix.\n\n\nPictures of the prototype feed arrangement can be provided soon. \nThey are on a camera not present here at this moment of writing.\n\n\nRemco PA3FYM\n\n\n\n\n\n",
    "attachments": []
}