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{
    "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/VPU4MUJKVGTJGH6PZ6IUT7M67XYP7P55/",
    "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/",
    "message_id": "007501c6c50d$4e20b190$6701a8c0@Mike2",
    "message_id_hash": "VPU4MUJKVGTJGH6PZ6IUT7M67XYP7P55",
    "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/UJ4VXVB5CFN2EIPPF4VUPLWA5DBYCJOI/",
    "sender": {
        "address": "n1jez (a) verizon.net",
        "mailman_id": null,
        "emails": null
    },
    "sender_name": "Mike Seguin",
    "subject": "[amsat-bb] Re: Mirage Preamp Setting",
    "date": "2006-08-21T10:33:49Z",
    "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/UJ4VXVB5CFN2EIPPF4VUPLWA5DBYCJOI/",
    "children": [],
    "votes": {
        "likes": 0,
        "dislikes": 0,
        "status": "neutral"
    },
    "content": "Hi Rick,\n\nHere's a simple method for determining the proper amount of gain for a \npreamp. It does talk about preamps with continuously adjustable gain, but \nyou should at least be able to get in the ballpark with your Mirage..... \nI've actually gone inside of some ARR's I've used and added a T pad to set \nthe gain... YMMV.\n\n73,\nMike N1JEZ\nAMSAT #29649\n\"A closed mouth gathers no feet\"\n\n====\nHere's a method that requires no test equipment at all. It comes from\nG4DGU, who designed all the original muTek transverters and outboard\npreamps to have adjustable gain. This method uses the sharp threshold\neffect of FM detectors at low S/N ratios, and it allows you to optimize\nthe preamp/transverter gain for your local band noise conditions.\n\n1. Turn the transverter/preamp gain well up.\n\n2. Find a very weak but steady unmodulated carrier (off-air, not from a\nsignal generator or a local birdie). Rotate the antenna until you can\njust detect the signal in FM mode.\n\n3. Reduce the preamp/transverter gain until you hear the noise increase.\nThe FM threshold is sensitive to a small fraction of a dB in S/N.\n\n4. Increase the gain just a little,to the point where you can't hear the\nquieting improve much.\n\n5. Switch back to a real DX mode.\n\nRemember that every dB of unnecessary preamp/transverter gain will\nprobably subtract almost 1dB from your system intermod intercept!\n\nThe penalty of adjusting the gain correctly is that you're living just\nabove the \"knee\" where S/N will begin to deteriorate rapidly if\nsomething changes. It's worthwhile to repeat this test every few months\n- especially just before a contest.\n\n73 from Ian G3SEK          Editor, 'The VHF/UHF DX Book'\n                          'In Practice' columnist for RadCom (RSGB)\n\n\n\n----- Original Message ----- \nFrom: \"Richard Lawn\" <[email protected]>\nSubject: [amsat-bb] Mirage Preamp Setting\n\n\n> I'm about to mast mount a new Mirage 70cm preamp. It has a high/low \n> setting.\n> Any suggestions from the group as I'm sure many of you are using this\n> preamp. Is the high setting too much gain? I got tired of forgetting I had\n> the ARR preamp on an frying it by sending too much RF into it.\n> 73\n> Rick\n> W2JAZ\n>\n> Richard Lawn, Dean\n> College of Performing Arts\n> University of the Arts\n> 215-717-6125\n\n",
    "attachments": []
}