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. 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
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 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.