For those that have Timelab the link to the E1938A PN measurement data is: https://dl.dropbox.com/u/59708595/E1938A.tim Bruce

On 09/29/2012 02:45 PM, Bruce Griffiths wrote: > For those that have Timelab the link to the E1938A PN measurement data is: > > https://dl.dropbox.com/u/59708595/E1938A.tim Thank you. I will measure mine so that we can compare them. Cross-correlation with a pair of BVAs should do it. Cheers, Magnus

Magnus Danielson wrote: > On 09/29/2012 02:45 PM, Bruce Griffiths wrote: >> For those that have Timelab the link to the E1938A PN measurement >> data is: >> >> https://dl.dropbox.com/u/59708595/E1938A.tim > > Thank you. I will measure mine so that we can compare them. > > Cross-correlation with a pair of BVAs should do it. > > Cheers, > Magnus > > I'm still a little suspicious of the result, although measuring a second E1938A removed from a Z3815A produced similar results. I'll measure one of them again with an isolation transformer to eliminate an LF earth loop to see if the earth loop was an issue. Using a single reference (PN floor < -170dBc/Hz) should suffice for this. I didnt have RF isolation transformers available at the time. I have since found that using a single point LF ground (rather than floating the entire interferometer) reduces the interferometer PN floor substantially. Bruce

Bruce Griffiths wrote: > Magnus Danielson wrote: >> On 09/29/2012 02:45 PM, Bruce Griffiths wrote: >>> For those that have Timelab the link to the E1938A PN measurement >>> data is: >>> >>> https://dl.dropbox.com/u/59708595/E1938A.tim >> >> Thank you. I will measure mine so that we can compare them. >> >> Cross-correlation with a pair of BVAs should do it. >> >> Cheers, >> Magnus >> >> > I'm still a little suspicious of the result, although measuring a > second E1938A removed from a Z3815A produced similar results. > I'll measure one of them again with an isolation transformer to > eliminate an LF earth loop to see if the earth loop was an issue. > Using a single reference (PN floor < -170dBc/Hz) should suffice for this. > I didnt have RF isolation transformers available at the time. > I have since found that using a single point LF ground (rather than > floating the entire interferometer) reduces the interferometer PN > floor substantially. > > Bruce > > > _______________________________________________ > 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. > Measuring the E1938A with a single point LF ground produces substantially the same result. A PN measurement using a different technique (classical mixer and low BW PLL) may be useful. Bruce

For those that don't have Timelab the attached image illustrates the artifacts in the E1938A phase noise plot. Bruce

The E1938A uses a crystal that is basically the same as the 10811 crystal except that it is in a reduced height package. However the phase noise is not as good as a 10811 due to broadband noise in the automatic frequency control circuit. By the time I discovered this, it was too late to try to fix it. Rick Karlquist N6RK E1938A designer

Hi Close in, it looks like it's pretty much the crystal and the loading of the bridge oscillator. Bob On Sep 29, 2012, at 11:46 PM, Richard (Rick) Karlquist <richard@karlquist.com> wrote: > The E1938A uses a crystal that is basically the same as > the 10811 crystal except that it is in a reduced height > package. However the phase noise is not as good as a > 10811 due to broadband noise in the automatic frequency > control circuit. By the time I discovered this, it > was too late to try to fix it. > > Rick Karlquist N6RK > E1938A designer > > _______________________________________________ > 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 recently modified an old 10811 to bring out the crystal leads on miniature coax (instead of having them connect to the oscillator circuit). This allowed me to measure the crystal's inherent flicker noise of frequency. The measurements indicate that the 10811 phase noise out to at least 100 Hz is entirely due to the crystal. An interesting aspect of flicker noise of frequency is that Allan deviation is independent of tau. Thus, just one number describes the crystal noise. Rick On 9/30/2012 4:44 AM, Bob Camp wrote: > Hi > > Close in, it looks like it's pretty much the crystal and the loading of the bridge oscillator. > > Bob > > On Sep 29, 2012, at 11:46 PM, Richard (Rick) Karlquist <richard@karlquist.com> wrote: > >> The E1938A uses a crystal that is basically the same as >> the 10811 crystal except that it is in a reduced height >> package. However the phase noise is not as good as a >> 10811 due to broadband noise in the automatic frequency >> control circuit. By the time I discovered this, it >> was too late to try to fix it. >> >> Rick Karlquist N6RK >> E1938A designer >> >> _______________________________________________ >> 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. > >

Rick it is really fantastic to see Time Nuts occasionally discuse different aspects of products they actually designed. This form is really a treasure. In the future it would be interesting to here how you would approach the next quartz industry standard. The next generation Blue-Top or BVA. Thanks; Thomas Knox > Date: Sun, 30 Sep 2012 10:03:03 -0700 > From: richard@karlquist.com > To: time-nuts@febo.com > Subject: Re: [time-nuts] E1938A PN measurments > > I recently modified an old 10811 to bring out the crystal > leads on miniature coax (instead of having them connect > to the oscillator circuit). This allowed me to measure > the crystal's inherent flicker noise of frequency. > The measurements indicate that the 10811 phase noise out > to at least 100 Hz is entirely due to the crystal. > An interesting aspect of flicker noise of frequency > is that Allan deviation is independent of tau. Thus, > just one number describes the crystal noise. > > Rick > > On 9/30/2012 4:44 AM, Bob Camp wrote: > > Hi > > > > Close in, it looks like it's pretty much the crystal and the loading of the bridge oscillator. > > > > Bob > > > > On Sep 29, 2012, at 11:46 PM, Richard (Rick) Karlquist <richard@karlquist.com> wrote: > > > >> The E1938A uses a crystal that is basically the same as > >> the 10811 crystal except that it is in a reduced height > >> package. However the phase noise is not as good as a > >> 10811 due to broadband noise in the automatic frequency > >> control circuit. By the time I discovered this, it > >> was too late to try to fix it. > >> > >> Rick Karlquist N6RK > >> E1938A designer > >> > >> _______________________________________________ > >> 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.

Hi ….. any bets on it being a triple oven? :) Bob On Sep 30, 2012, at 1:26 PM, Tom Knox <actast@hotmail.com> wrote: > > Rick it is really fantastic to see Time Nuts occasionally discuse different aspects of products they actually designed. This form is really a treasure. > In the future it would be interesting to here how you would approach the next quartz industry standard. The next generation Blue-Top or BVA. > Thanks; > Thomas Knox > > > >> Date: Sun, 30 Sep 2012 10:03:03 -0700 >> From: richard@karlquist.com >> To: time-nuts@febo.com >> Subject: Re: [time-nuts] E1938A PN measurments >> >> I recently modified an old 10811 to bring out the crystal >> leads on miniature coax (instead of having them connect >> to the oscillator circuit). This allowed me to measure >> the crystal's inherent flicker noise of frequency. >> The measurements indicate that the 10811 phase noise out >> to at least 100 Hz is entirely due to the crystal. >> An interesting aspect of flicker noise of frequency >> is that Allan deviation is independent of tau. Thus, >> just one number describes the crystal noise. >> >> Rick >> >> On 9/30/2012 4:44 AM, Bob Camp wrote: >>> Hi >>> >>> Close in, it looks like it's pretty much the crystal and the loading of the bridge oscillator. >>> >>> Bob >>> >>> On Sep 29, 2012, at 11:46 PM, Richard (Rick) Karlquist <richard@karlquist.com> wrote: >>> >>>> The E1938A uses a crystal that is basically the same as >>>> the 10811 crystal except that it is in a reduced height >>>> package. However the phase noise is not as good as a >>>> 10811 due to broadband noise in the automatic frequency >>>> control circuit. By the time I discovered this, it >>>> was too late to try to fix it. >>>> >>>> Rick Karlquist N6RK >>>> E1938A designer >>>> >>>> _______________________________________________ >>>> 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.