Hi > On Jan 6, 2018, at 4:31 PM, Joseph Gwinn <[email protected]> wrote: > >> ------------------------------ >> >> Message: 2 >> Date: Sat, 6 Jan 2018 09:19:31 -0500 >> From: Bob kb8tq <[email protected]> >> To: Discussion of precise time and frequency measurement >> <[email protected]> >> Subject: Re: [time-nuts] AM vs PM noise of signal sources >> Message-ID: <[email protected]> >> Content-Type: text/plain; charset=utf-8 >> >> Hi >> >> The key point missing is the fact that any real oscillator must have >> a limiter >> in the loop. Otherwise it will “create one” by going over the max >> output of this or >> that amplifier. To the degree that the limiter has issues (limits >> poorly) you will get >> AM noise. > > Hmm. Not strictly true. One can also use an AGC loop, like a wein > bridge oscillator. That said, some kind of softish limiter is commonly > used. > > Joe Gwinn >
…. and a “soft” limiter (like an AGC) likely will result in some very interesting noise showing up on the output. Bob > > >> On a practical basis, loop Q is as significant as resonator Q . The various >> elements in the loop degrade the total Q by a significant amount. >> Getting 25 to >> 50% of the resonator Q is “doing well” with his or that common >> circuit. Yes, there >> are even more layers past this …. >> >> Bob >> >>> On Jan 6, 2018, at 1:53 AM, donald collie <[email protected]> wrote: >>> >>> So to be lowest noise, an oscillator should have the highest Q resonator >>> possible in its feedback loop, operate in class "A" [for maximum >>> linearity], and utilise active amplifier device(s) that contribute the >>> least noise [both amplitude, or 1/f], and phase. This latter implies >>> operating the active device at maximum output level [ie signal to noise]. >>> The quality of the power supply effects the amplifier SNR, so in the >>> persuit of superlative oscillator phase noise, the power supply should be >>> as good as possible. >>> Resistors in the oscillator carrying DC make 1/f noise - the best in this >>> respect are the metal type, I think - so use metal resistors or WW. >>> What are the other conciderations that come into the design, for lowest >>> noise of the oscillator itself >>> Split, then >>> lump...;-).................................................Cheers, de : Don >>> ZL4GX >>> > >> End of time-nuts Digest, Vol 162, Issue 10 >> ****************************************** > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
