Not necessarily so.. My HP Z3815A here (desktop unit) has horrible phase noise and massive spurs. Really to cry over since I know what the internal OCXO (1938A type) is capable of generating. See the attached plot. bye, Said In a message dated 11/26/2010 16:37:26 Pacific Standard Time, GandalfG8@aol.com writes: So if I want a really souped-up freq standard for my lab, then I should concentrate on finding the best oxco I can (which may be disciplined by the GPS or manually occasionally calibrated to GPS), and use the best power supply I can find. These seem to be what I should concentrate on rather than more channels. I do believe that I read some stuff on the internet that the HP GPS DO's do seem to have very good power supplies (or converters) which contribute to low spurs. So it seems the HP's do have a real advantage (not just the name).

Those switch mode regulator modules under the finned heatsinks in the Z3815A are likely responsible for most of the spurs. The ECL/CML logic dividers and the various ouputs like 19.6608MHz also contribute. Since the E1938A output is only +4dBm, its very easy to degrade the phase noise in the buffer chain if one isnt careful. With careful design a discrete buffer amp phase noise floor below -170dBc/Hz should be possible with a + 4dBm input. Bruce SAIDJACK@aol.com wrote: > Not necessarily so.. > > My HP Z3815A here (desktop unit) has horrible phase noise and massive > spurs. Really to cry over since I know what the internal OCXO (1938A type) is > capable of generating. > > See the attached plot. > > bye, > Said > > > In a message dated 11/26/2010 16:37:26 Pacific Standard Time, > GandalfG8@aol.com writes: > > So if I want a really souped-up freq standard for my lab, then I should > concentrate on finding the best oxco I can (which may be disciplined by > the > GPS or manually occasionally calibrated to GPS), and use the best power > supply I can find. These seem to be what I should concentrate on rather > than more channels. > > I do believe that I read some stuff on the internet that the HP GPS DO's > do > seem to have very good power supplies (or converters) which contribute to > low spurs. So it seems the HP's do have a real advantage (not just the > name). > > > > > > _______________________________________________ > 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.

I wonder if the 19.6608 isn't needed, if one could unsolder the logic divider chips and reduce noise? 73 Eugene W2HX -----Original Message----- From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Bruce Griffiths Sent: Saturday, November 27, 2010 12:44 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] ok, newbie questions Those switch mode regulator modules under the finned heatsinks in the Z3815A are likely responsible for most of the spurs. The ECL/CML logic dividers and the various ouputs like 19.6608MHz also contribute. Since the E1938A output is only +4dBm, its very easy to degrade the phase noise in the buffer chain if one isnt careful. With careful design a discrete buffer amp phase noise floor below -170dBc/Hz should be possible with a + 4dBm input. Bruce SAIDJACK@aol.com wrote: > Not necessarily so.. > > My HP Z3815A here (desktop unit) has horrible phase noise and massive > spurs. Really to cry over since I know what the internal OCXO (1938A type) is > capable of generating. > > See the attached plot. > > bye, > Said > > > In a message dated 11/26/2010 16:37:26 Pacific Standard Time, > GandalfG8@aol.com writes: > > So if I want a really souped-up freq standard for my lab, then I should > concentrate on finding the best oxco I can (which may be disciplined by > the > GPS or manually occasionally calibrated to GPS), and use the best power > supply I can find. These seem to be what I should concentrate on rather > than more channels. > > I do believe that I read some stuff on the internet that the HP GPS DO's > do > seem to have very good power supplies (or converters) which contribute to > low spurs. So it seems the HP's do have a real advantage (not just the > name). > > > > > > _______________________________________________ > 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.

On 11/27/2010 06:22 PM, W2HX wrote: > I wonder if the 19.6608 isn't needed, if one could unsolder the logic > divider chips and reduce noise? True, it would not be too hard, but I don't think it would explain the wood of spikes in that phase noise graph. There are many other sources of noise in there. Right now my Z3815A is borrowed to Björn, so I can't sniff around like I would do. For a box like this there should be a number of possible noise sources, so no single fix will be the cure. Cheers, Magnus

Said - Hope you had a great Thanksgiving. I would think that buffer better be real good. Otherwise it could impact the loop characteristics, since the OCXO output is sampled and fed back. Regards - mike Mike B. Feher, EOZ Inc. 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 office 908-901-9193 cell -----Original Message----- From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On Behalf Of Said Jackson Sent: Saturday, November 27, 2010 1:22 PM To: w2hx@w2hx.com; Discussion of precise time and frequency measurement Cc: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] ok, newbie questions I was thinking to tap-off the Ocxo itself with a small buffer and bypass all of the internal stuff. Will report on that later.. Sent from my iPad

I was thinking to tap-off the Ocxo itself with a small buffer and bypass all of the internal stuff. Will report on that later.. Sent from my iPad On Nov 27, 2010, at 9:22, "W2HX" <w2hx@w2hx.com> wrote: > I wonder if the 19.6608 isn't needed, if one could unsolder the logic > divider chips and reduce noise? > > 73 Eugene W2HX > > > -----Original Message----- > From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On > Behalf Of Bruce Griffiths > Sent: Saturday, November 27, 2010 12:44 AM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] ok, newbie questions > > Those switch mode regulator modules under the finned heatsinks in the > Z3815A are likely responsible for most of the spurs. > The ECL/CML logic dividers and the various ouputs like 19.6608MHz also > contribute. > > Since the E1938A output is only +4dBm, its very easy to degrade the > phase noise in the buffer chain if one isnt careful. > With careful design a discrete buffer amp phase noise floor below > -170dBc/Hz should be possible with a + 4dBm input. > > Bruce > > SAIDJACK@aol.com wrote: >> Not necessarily so.. >> >> My HP Z3815A here (desktop unit) has horrible phase noise and massive >> spurs. Really to cry over since I know what the internal OCXO (1938A type) > is >> capable of generating. >> >> See the attached plot. >> >> bye, >> Said >> >> >> In a message dated 11/26/2010 16:37:26 Pacific Standard Time, >> GandalfG8@aol.com writes: >> >> So if I want a really souped-up freq standard for my lab, then I should >> concentrate on finding the best oxco I can (which may be disciplined by >> the >> GPS or manually occasionally calibrated to GPS), and use the best power >> supply I can find. These seem to be what I should concentrate on rather >> than more channels. >> >> I do believe that I read some stuff on the internet that the HP GPS DO's >> do >> seem to have very good power supplies (or converters) which contribute > to >> low spurs. So it seems the HP's do have a real advantage (not just the >> name). >> >> >> >> >> >> _______________________________________________ >> 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.