Path: csiph.com!eternal-september.org!feeder.eternal-september.org!mx02.eternal-september.org!.POSTED!not-for-mail From: jimp@specsol.spam.sux.com Newsgroups: sci.physics Subject: Re: long antenna Date: Sun, 22 Nov 2015 23:16:22 -0000 Organization: A noiseless patient Spider Lines: 131 Sender: Jim Pennino Message-ID: <6vu9ic-bgi.ln1@mail.specsol.com> References: <4736856.kWDMch3Bm0@PointedEars.de>

<2a30ic-rud.ln1@mail.specsol.com> <0th1ic-34j.ln1@mail.specsol.com> Injection-Info: mx02.eternal-september.org; posting-host="db4120ef82bbc153014637d4cd15a795"; logging-data="8822"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18OoQHd1ZVwFd0kKHLOS8AI" User-Agent: tin/2.2.1-20140504 ("Tober an Righ") (UNIX) (SunOS/5.10 (i86pc)) Cancel-Lock: sha1:7q3GeSN/hBswhN2I2RHswmbesuo= Xref: csiph.com sci.physics:534639 gilber34 wrote: > On 11/19/2015 12:44 PM, jimp@specsol.spam.sux.com wrote: >> gilber34 wrote: >>> On 11/18/2015 11:29 PM, jimp@specsol.spam.sux.com wrote: >>>> gilber34 wrote: >>>>> On 11/18/2015 5:15 PM, jimp@specsol.spam.sux.com wrote: >>>>>> gilber34 wrote: >>>>>>> On 11/18/2015 3:56 PM, Thomas 'PointedEars' Lahn wrote: > > >>>>> one can use an antenna with a preamp and forget matching, however the >>>>> preamp will be a mixer, with the LO supplied by FM, TV stations or other >>>>> if around, providing inteference. >>>> >>>> Total nonnsense. >>> >>> not at all, the typical tradeoff in designing preamps, how much gain, in >>> how much selectivity (bandwidth), how much NF. >>> Typical in the below 30MHz RF preamps is no antenna matching, other >>> factors dominate. >> >> Nope. > > have to match transmitter, below 30 MHz receiver preamps not much need > at all. Preamps have nothing to do with transmitters. A switchable preamp is very handy; switch in it when signal levels are low and out when there are strong signals that would cause overload. >>>> >>>> Mixing requires a non-linear device and preamps are built to be linear >>>> devices. >>> >>> preamps are linear only in a range, outside this range all preamps are >>> mixers. And even in their linear range, they also provide gain to other >>> signals in their bandwidth, which also cause following stages to be over >>> driven, to become mixers. >> >> Arm waving. > > this is stuff experienced RF designers know, not the Hams, or amateur > radio people what is left of them. This is very basic RF that you can find in the Radio Amateurs Handbook. I suggest you read it. >>> >>> If you put a +20dB preamp on your FM radio, it will trash it out totally. >> >> This just shows you haven't a clue why one would use a preamp. >> > > so you are recommending using +20dB preamp for FM radios ? No, I am saying you don't know what you are talking about. >>>> Matchins still important to preamps. >>> >>> and so is intentional mis-matching, important to provide stability, and >>> loading for front end filters, and finding best NF, a tradeoff >>> typically. Depends on the band and application. >> >> Nope. > > well, that is RF design, not amateur radio sandbox tinkering. Nope, it is babbling word salad. >>>> >>>> Most of that is just nonsense. >>> >>> I see you are unfamiliar with FM radio. >>> "Capture" is also closely related to "takeover gain" >>> That is why FM sounds so much better than AM. >> >> Nope. >> >> Clueless. >> >> FYI, FM sounds better than AM (for broadcast) because the allowed bandwidth >> is much higher. It has little to nothing to do with the modulation other >> than FM is static resistant. > > Why is FM "static resistant" ? Capture effect. Nope, it is because static is primarily AM. > Guess you should take some time and refresh yourself. Guess you still haven't a clue what you are talking about. >> >>> https://www.physicsforums.com/threads/fm-modulation-capture-effect.747206/ >>> >>>> >>>>> he said he was listening to FM, so he is in a city, >>>> >>>> There are lots of FM stations outside major cities these days. >>> >>>>> but break out your spectrum analyser and see how huge the FM station >>>>> power is, larger than any other, except for some TV channels >>>>> >>>>> I would do it and send a photo, but my analyser when last turned on, let >>>>> out some smoke in the back, and no workie now. (smoked a resistor in the >>>>> power section somewhere) >>>> >>>> >>>> Not surprising given your level of RF knowledge. >>> >>> no it is a nice but older 10KHz to 22GHz Unit, easy to fix smoked >>> resistor, but a 100#der almost a boat anker. >>> but Troll on if you must, but you could contribute too. >> >> OK. >> >> Go buy a copy of the Radio Amateurs Handbook and read it. >> > > that is for Amateurs, 1960's stuff, and didn't they quit printing that > a while back ? Nope, it is kept up to date and is far above your demonstrated technical level. -- Jim Pennino