I`m looking at the circuit of an H/P10544 oscillator - can anybody confirm, please, if the H'P transistor types : 53-20, and 54-215 have commercial equivalents? Thankyou.................................................... ............................................................ ............................................................ ...............................................Don.
On Mon, Jan 8, 2018 at 1:02 AM, donald collie <[email protected]> wrote: > Does any limiter, soft or hard, [and perhaps any nonlinearity of power > term 3 or greater in the amplifier of an oscillator] cause the "baseband > 1/f noise to translate up to the resonator frequency [a form of > crossmodulation]?. I wonder this because > phase noise vs freq plots look a bit like the 1/f plots of a resistor, or > active device, or power supply. Ceramic caps, and resonators [I`m thinking > of quartz crystals] don`t pass much DC, and as I understand it, 1/f noise > is associated with dc passing through resistors, or semiconductors. So the > best way to go might be to have a very linear amplifier, which exhibits > very low noise [perhaps 150dB below the operating level], with an AGC loop, > that sets the operating levela little below the level at which the amp > starts to clip - this could be done with a thermistor to avoid the AGC loop > altering the [optimised] operating conditions of the amp. Alternatively you > might be able to use a tetrode device like a dual gate MOSFET, and apply > the AGC to the second gate. Thus you could keep the extremely linear amp > extremely linear. [150dB below 1Volt RMS is 0.032uV RMS]. > Cheers!..................................................... > ............................................................ > .......................................................Don ZL4GX > > > <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> > Virus-free. > www.avg.com > <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail> > <#m_3433364989741243603_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> > > On Sun, Jan 7, 2018 at 3:12 PM, Dana Whitlow <[email protected]> > wrote: > >> One point about oscillator design I've not yet seen mentioned is this: the >> limiter >> must not degrade the resonator Q when in action. Hence, a pair of diodes >> connected in parallel back to back, across a shunt resonator, would be a >> bad >> thing to do from the perspective of low phase noise. A differential >> amplifier >> that limits by running out of current on peaks, driving a shunt resonator, >> is >> a much better way even though one pays a price in having more transistor >> noise in the circuit. >> >> I've long wondered if a very slow AGC might avoid the nonlinear mechanisms >> issue except, of course, for things happening within the AGC loop's >> bandwidth. >> Is anybody reading this aware of what the truth really is? >> >> Dana >> >> >> On Sat, Jan 6, 2018 at 4:29 PM, Magnus Danielson < >> [email protected] >> > wrote: >> >> > >> > >> > On 01/06/2018 10:31 PM, Joseph Gwinn 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. >> > >> > Regardless what non-linear mechanism in play, this remains a non-linear >> > mechanism that achieves the goal. Choose wisely. >> > >> > Cheers, >> > Magnus >> > _______________________________________________ >> > 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/m >> ailman/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.
