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{ "url": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/7E4APU2MEKIR6ER2SDRHFRLWVBFPPUKA/?format=api", "mailinglist": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/?format=api", "message_id": "[email protected]", "message_id_hash": "7E4APU2MEKIR6ER2SDRHFRLWVBFPPUKA", "thread": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/thread/GVJ7SDRSJGMRHEZZRY74DVZPULRBRBPB/?format=api", "sender": { "address": "nate (a) natetech.com", "mailman_id": null, "emails": null }, "sender_name": "Nate Duehr", "subject": "[amsat-bb] Re: New Preamp", "date": "2007-09-20T21:14:59Z", "parent": "https://mailman.amsat.org/hyperkitty/api/list/[email protected]/email/ZZMZHT3HVZOQXVMUN3QR6WWHTOP672RZ/?format=api", "children": [], "votes": { "likes": 0, "dislikes": 0, "status": "neutral" }, "content": "Gary Memory wrote:\n\n> The only thing I would add to your comments is that to amplify signals\n> before an existing front, with a given antenna and feed line, can't help but\n> have a negative impact somewhere else. Maybe that negative is no big deal.\n\nI haven't jumped into this conversation, but really the issue is that a \nlot of hams seem to want to \"do it once, and never change it\" or they \nwant someone ELSE to do the experimentation, real measurements, and WORK \nfor them. They want \"Plug and Play\"... instant gratification.\n\nThis leads to endless online debates by those who WON'T go DO, and keeps \nthe rest of us who HAVE played with pre-amps and the resulting \nreal-world complexity from even commenting.\n\nYou might see a \"XYZ setup works great for me, but...\" from a few \npeople, but not many -- when these threads come up.\n\nThe reality is, designing an RF *SYSTEM* for a particular location, site \nnoise floor, receiver, transmitter power level, etc... and making it \nperform to the absolute best that it theoretically can -- is hard work, \n that many simply aren't willing to do.\n\nRF Engineers/Professional RF Technicians get paid big bucks to do this \nlevel of work in non-Amateur systems, and many are also Amateurs, so \nthey benefit from their knowledge and experience, and know WHICH \ntrade-offs they'd like to make... since every particular setup of any \ncomplete RF system, always has a few.\n\n> The less stages of anything before demodulation, the better chances you have\n> at a super receive chain. And with another stage of amplification or a\n> preamp, certainly you just have to hope that no strong signal will come up\n> anywhere nearby in frequency or distance to what your receiver is set to.\n> What about dynamic range....wouldn't a preamp toss that into the toilet?\n> Again, maybe it is no big deal to the end you are after.\n\nYep, you just HAVE to measure, make a theory, test that theory via \nexperimentation, and then wash-rinse-repeat until you're either happy \nwith the result, or you've run out of ideas.\n\n> My advice about advice is this: Listen to others, study and learn about it\n> yourself, and then go do whatever you want. In the world of radio, no\n> amount of paperwork, planning and talking beats trying it to see if it\n> works. I have several preamps of all kinds and I use them whenever\n> possible, but I realize their limitations.\n\nDepends on your knowledge level. Those who've \"been there done that\" \ncan always benefit from running the numbers ahead of time and planning, \nwhile taking their experience into account.\n\nSome *might* even share what \"works for them\" as some do, but your \nadvice is dead-on for newbies. Go try something, learn how to measure \nit properly, learn the math, and get hard numbers to see how YOUR \nstation works out.\n\n(And frankly, since a lot of us are \"just Amateurs\" one of the distinct \nreasons that some of us don't pipe up and say anything is because we \ndon't feel comfortable with the math, or whatever reason... we're not \n\"classically trained\" as they say, and people that are sometimes \naccidentally come across as harsh when they correct mistakes in online \nforums... I say accidental, because I've done it on other topics, and \ndidn't know I hurt someone's feelings.)\n\n> Finally, to those who sent some perty nasty comments via private mail re\n> this thread...Gee...I am sorry. Really I am. I had no idea my comments\n> were so flammable. I'm betting that stealing your wife or girlfriend\n> (boyfriend?) would not be as traumatic? What can I say? I didn't mean to\n> cause trouble. To me, this is a hobby. A fun pastime. I promise, I won't\n> make comments again. I rarely do make comments on this board...because\n> every time I do, there are those who take it so seriously. Geezzooo!\n\nThis is what really made me want to comment. Ignore the cowards behind \ntheir keyboards who can't be civil. So many people do this, that there \nare psychological studies about how people's personalities change when \nthey feel \"safe\" from retribution behind a keyboard and a screen. In \nany \"normal\" multiple-person conversation they'd either be shunned or \nsomeone would hit them upside the head with a clue-bat. But anyway, it \nreally isn't worth worrying about them.\n\nLet 'em be unhappy, that's their choice to be sour/mean/whatever, and \nhas no impact on you, if you don't allow it to. It's just an extension \nof their own reality, and once you realize that, you realize that some \npeople live in very drab/angry/sad worlds of their own creation. Not \nmuch fun.\n\nBack to the pre-amps and duplex operation, for those that have never \nworked on them, remember that people building repeaters do exactly \nthat... all the time. And most add pre-amps in some fashion or another \nto their repeater systems (as someone pointed out, many commercial FM \nrigs only do anywhere from .2uV - .3uV sensitivity for 12dB SINAD (since \nwe are talking about FM at the moment, you gotta have that 12dB SINAD \nreference point), and repeater owners/operators everywhere want better \nreceivers than THAT!\n\nThere's tons of information on the Net and in books about how to duplex \na repeater system, while maintaining high receiver sensitivity, and \npushing lots of power out the TX side... which are all similar goals to \nwhat Satellite ops are trying to do, perhaps.\n\nI only mention this as a reminder to those that hadn't thought about it, \nthat sites like http://www.repeater-builder.com and others have lots of \n\"basic starting point\" information about that type of setup and how to \nmeasure it... just change \"repeater transmitter\" to \"uplink\", and \n\"repeater receiver\" to \"downlink\" in your mind and keep in mind that \nyou're often not on the same BAND in satellite operations for those two \nfrequencies, so duplexer/filter stuff won't be \"quite right\"...\n\nBut, it gives your brain a frame of reference to get your head around \nthe measurements the super-smart folks are doing on their RF systems.\n\nAnd most of all, folks gotta remember to HAVE FUN with all this stuff... \nit's not a job, it's a hobby... And it's not even more important than \nthe family dog, when the dog is sick and needs to go to the vet.\n\nNate WY0X\n", "attachments": [] }