Yes, that is what I figured regarding the 12V. For me, it has more or less been a rule of thumb, but, I think at 10 MHz the best you could do, due to Q and transistor noise and gain, was about - 155 dBc/Hz at about 100 Hz from the carrier. I do not recall from your earlier post what you are actually measuring. I would think anything close to - 150 dBc/Hz would be very good. That is of course if you can even measure it at its fundamental frequency. - Mike
Mike B. Feher, N4FS 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Henk ten Pierick Sent: Tuesday, January 01, 2008 9:20 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] xtal oscillator phase noise On Jan 1, 2008, at 14:13, Mike Feher wrote: > The emitter follower should have a very low output impedance, so, I > would > not be too concerned about it's driving capabilities. If you must > have 50 > ohms, well, then just connect a 47 ohm resistor after the 1 nf > capacitor and > measure it there, without U1. Yes > The confusing thing about the ADR455 is that > above, on the schematic, you claimed you derived the 12V from the > ADR455. I > am not familiar with it, but, in that case, how did you get the 12 > V from > the 5 volt reference? - Mike Sorry for the confusion. The 12 volt is derived from the 5 volt reference by a simple circuit, the usual series regulator build with discrete transistors. It will add some noise to the noise of the ADR455. > Mike B. Feher, N4FS > 89 Arnold Blvd. > Howell, NJ, 07731 > 732-886-5960 > > > > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:time-nuts- > [EMAIL PROTECTED] On > Behalf Of Henk ten Pierick > Sent: Tuesday, January 01, 2008 8:03 AM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] xtal oscillator phase noise > > On Jan 1, 2008, at 13:42, Mike Feher wrote: > >> Henk - >> >> Did you try to measure the PN out of the oscillator directly >> without the >> buffer amp (U1)? > > No, but I will do it. I have to find a way, the emitter follower is > not expected to drive 50 ohm. > >> Also, what is the voltage from V1? Is it also 12V? > > The ADR455 is a 5volt reference. > >> HNY - > > Same to you all. > > Henk > >> Mike >> >> >> >> Mike B. Feher, N4FS >> 89 Arnold Blvd. >> Howell, NJ, 07731 >> 732-886-5960 >> >> >> -----Original Message----- >> From: [EMAIL PROTECTED] [mailto:time-nuts- >> [EMAIL PROTECTED] On >> Behalf Of Henk ten Pierick >> Sent: Tuesday, January 01, 2008 7:25 AM >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] xtal oscillator phase noise >> >> >> On Dec 30, 2007, at 3:42, Bruce Griffiths wrote: >> >>> Henk >>> >>> The 30dB/decade phase noise slope could be the result of the >>> effect of >>> low pass filtering a power supply or reference source that has >>> significant flicker noise. >> >> The reference used is an ADR455. I have not seen references >> significant better. Suggestions? >> >>> Lack of local RF feedback and /or high dc gain from base to >>> collector in >>> BJT buffer stages can produce significant flicker phase noise. >> >> I have now doubled the dc voltage for the oscillating transistor for >> the reduction of junction capacitances. It had no result on phase >> noise. >> >> Is low hfe better for phase noise? >> >> Henk >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ >> time-nuts >> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/ > time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.