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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/HQJKFTFNZIFGY4MSAA5U3K6UFX7T2EZI/?format=api",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api",
    "message_id": "[email protected]",
    "message_id_hash": "HQJKFTFNZIFGY4MSAA5U3K6UFX7T2EZI",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/TKENCMNBU36DZDVATSKIAGAZOYZM3WVK/?format=api",
    "sender": {
        "address": "stanw1le (a) verizon.net",
        "mailman_id": "cde59a7de6874af3b354fb231df89b4c",
        "emails": "https://mailman.amsat.org/hyperkitty/api/sender/cde59a7de6874af3b354fb231df89b4c/emails/?format=api"
    },
    "sender_name": "Stan, W1LE",
    "subject": "[amsat-bb] Re: fun with preamps",
    "date": "2010-03-16T00:02:54Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/TKENCMNBU36DZDVATSKIAGAZOYZM3WVK/?format=api",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Hello Bob,\n\nDoes the preamplifier have a internal gain control ?\n\nIf it does, back it off at ~ 6 S units.\n\nExcess gain only reduces the system dynamic range.\n\nThe real test is with a SINAD meter or a NF meter, injecting a test \nsignal up at the preamplifier input,\nand reducing gain until NF or SINAD sensitivity is just barely degraded.\nThat will be the point of best S/N, (best sensitivity).\n\nMost of the S7 reading you have is just noise, not signal.\n\nThe preamplifier could be defective and performance is out of spec.\nWhatever that spec is, I do not recall ever seeing a ICOM AG-25/35 \nperformance spec.\n\nIf the preamplifier is a multi stage unit, the first stage which sets \nthe system noise figure\ncould be defective/soft and the second stage just amplifies the noise \nahead of it.\n\nMost convincing would be a NF test with professional meter.\n\nSend it to me and I will test for free. I will NOT repair. I will NOT \nopen it.\nInclude return postage if you want it returned (HI).\n\nI will provide you a plot of the NF and gain performance using\na HP-8970B Noise Figure Meter and HP-346C Noise source.\n\nOf course, this offer is open to any other AMSAT member.\nE-mail me for details.\n\nWhat do you say ?\n\nStan, W1LE    Cape Cod     FN41sr\n\n\n\n\nBob- W7LRD wrote:\n> Hello \n>\n> Just installed a AG-25 (Icom preamp) on my 2M cp yagi.  No preamp noise Smeter=0, preamp on Smeter=7.  Signals \"appear\" better after backing down the volume with the preamp.  I have 8-10 feet of LMR400uf from antenna to preamp, 50 feet of LMR400 to shack.  I suppose I was expecting more \"dramatic\" results, I realize the AG-25 isn't the greatest and best, but it works well with the 910.  Are these real world results for what I have.  S7 noise level seems a bit high. \n>\n> as always-thanks \n>\n> 73 Bob W7LRD \n> _______________________________________________\n> Sent via [email protected]. Opinions expressed are those of the author.\n> Not an AMSAT-NA member? Join now to support the amateur satellite program!\n> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb\n>   \n\n",
    "attachments": []
}