Discussion:
Oscilloscope-based measurements of frequency stability
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Dana Whitlow
2018-10-01 12:45:31 UTC
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Permalink
I cheered when I saw Dave B's "silly question", for
then I realized that I'm not the only one who likes
to measure things with an o'scope.

I had purchased a GPSDO a few weeks before and
had been observing its behavior relative to a free-
running Rb by watching 10 MHz sinewaves drift with
respect to each other as an aid in setting the Rb's
frequency. However, I was seeing enough fairly
rapid random drift to limit the usefulness of this kind
of observation. It dawned on me that I was sometimes
seeing drifts of several ns over the course of just
several seconds, thus implying that sometimes the
relative frequency error between the two sources was
reaching as high as roughly 1E-9. I wanted to be able
to capture and plot a somewhat extended run of data
so I could try to understand this behavior better.

Being TIC-less, I decided to see what I could do with
my o'scope, which is a Chinese-made 2-channel DSO
with synchronous sampling by the two channels and
with a respectable trace memory depth (28 MSA per
channel).

I began this effort in earnest a couple of days before I
saw Dave's question, and have only now brought it to
a sufficient state of completion to feel justified in reporting
some results.

I am presently able to record about 45 minute's worth of
data as limited by the 'scope's trace memory, but my XP
computer's RAM space limits me to processing only about
35 minutes of that in a seamless run. Over that time
span I've seen a peak relative frequency discrepancy of
about 1.4E-9, with a handful reaching or exceeding 1E-9.
I've also measured average frequency differences between
the source's a a few parts in 10E11.

Most of the effort went into developing a C program to do
the processing and then correctly scaling and displaying
the results in a form which I considered useful to me. This
processing of course had to deal with an off-frequency and
drifting 'scope timebase, which is *horrible* compared to the
quantities under measurement (as expected from the outset).

Present indications are that at this level of GPSDO mis-
behavior, the results I'm viewing are about 20 dB higher
than the basic floor, which I am still characterizing. I
believe that the floor is limited primarily by uncorrelated
sampling jitter between the two 'scope channels.

If there is an expression of interest in this technique, I'll
publish a detailed description of the technique and some
plots showing results, probably in the form of an attachment
in pdf format.

Dana
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Christoph Kopetzky
2018-10-01 14:08:12 UTC
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Chris Burford
2018-10-01 13:20:30 UTC
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This sounds interesting enough and I would appreciate any notes or insight on doing this. I have a PRS10 and several GPSDOs that I would like to evaluate for performance on my scope.

Many thanks.


---- Dana Whitlow <***@gmail.com> wrote:
> I cheered when I saw Dave B's "silly question", for
> then I realized that I'm not the only one who likes
> to measure things with an o'scope.
>
> I had purchased a GPSDO a few weeks before and
> had been observing its behavior relative to a free-
> running Rb by watching 10 MHz sinewaves drift with
> respect to each other as an aid in setting the Rb's
> frequency. However, I was seeing enough fairly
> rapid random drift to limit the usefulness of this kind
> of observation. It dawned on me that I was sometimes
> seeing drifts of several ns over the course of just
> several seconds, thus implying that sometimes the
> relative frequency error between the two sources was
> reaching as high as roughly 1E-9. I wanted to be able
> to capture and plot a somewhat extended run of data
> so I could try to understand this behavior better.
>
> Being TIC-less, I decided to see what I could do with
> my o'scope, which is a Chinese-made 2-channel DSO
> with synchronous sampling by the two channels and
> with a respectable trace memory depth (28 MSA per
> channel).
>
> I began this effort in earnest a couple of days before I
> saw Dave's question, and have only now brought it to
> a sufficient state of completion to feel justified in reporting
> some results.
>
> I am presently able to record about 45 minute's worth of
> data as limited by the 'scope's trace memory, but my XP
> computer's RAM space limits me to processing only about
> 35 minutes of that in a seamless run. Over that time
> span I've seen a peak relative frequency discrepancy of
> about 1.4E-9, with a handful reaching or exceeding 1E-9.
> I've also measured average frequency differences between
> the source's a a few parts in 10E11.
>
> Most of the effort went into developing a C program to do
> the processing and then correctly scaling and displaying
> the results in a form which I considered useful to me. This
> processing of course had to deal with an off-frequency and
> drifting 'scope timebase, which is *horrible* compared to the
> quantities under measurement (as expected from the outset).
>
> Present indications are that at this level of GPSDO mis-
> behavior, the results I'm viewing are about 20 dB higher
> than the basic floor, which I am still characterizing. I
> believe that the floor is limited primarily by uncorrelated
> sampling jitter between the two 'scope channels.
>
> If there is an expression of interest in this technique, I'll
> publish a detailed description of the technique and some
> plots showing results, probably in the form of an attachment
> in pdf format.
>
> Dana
> _______________________________________________
> time-nuts mailing list -- time-***@lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.

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Bryan _
2018-10-01 18:40:13 UTC
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Interested as well

-=Bryan=-

________________________________
From: time-nuts <time-nuts-***@lists.febo.com> on behalf of Chris Burford <***@austin.rr.com>
Sent: October 1, 2018 6:20 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Oscilloscope-based measurements of frequency stability

This sounds interesting enough and I would appreciate any notes or insight on doing this. I have a PRS10 and several GPSDOs that I would like to evaluate for performance on my scope.

Many thanks.


---- Dana Whitlow <***@gmail.com> wrote:
> I cheered when I saw Dave B's "silly question", for
> then I realized that I'm not the only one who likes
> to measure things with an o'scope.
>
> I had purchased a GPSDO a few weeks before and
> had been observing its behavior relative to a free-
> running Rb by watching 10 MHz sinewaves drift with
> respect to each other as an aid in setting the Rb's
> frequency. However, I was seeing enough fairly
> rapid random drift to limit the usefulness of this kind
> of observation. It dawned on me that I was sometimes
> seeing drifts of several ns over the course of just
> several seconds, thus implying that sometimes the
> relative frequency error between the two sources was
> reaching as high as roughly 1E-9. I wanted to be able
> to capture and plot a somewhat extended run of data
> so I could try to understand this behavior better.
>
> Being TIC-less, I decided to see what I could do with
> my o'scope, which is a Chinese-made 2-channel DSO
> with synchronous sampling by the two channels and
> with a respectable trace memory depth (28 MSA per
> channel).
>
> I began this effort in earnest a couple of days before I
> saw Dave's question, and have only now brought it to
> a sufficient state of completion to feel justified in reporting
> some results.
>
> I am presently able to record about 45 minute's worth of
> data as limited by the 'scope's trace memory, but my XP
> computer's RAM space limits me to processing only about
> 35 minutes of that in a seamless run. Over that time
> span I've seen a peak relative frequency discrepancy of
> about 1.4E-9, with a handful reaching or exceeding 1E-9.
> I've also measured average frequency differences between
> the source's a a few parts in 10E11.
>
> Most of the effort went into developing a C program to do
> the processing and then correctly scaling and displaying
> the results in a form which I considered useful to me. This
> processing of course had to deal with an off-frequency and
> drifting 'scope timebase, which is *horrible* compared to the
> quantities under measurement (as expected from the outset).
>
> Present indications are that at this level of GPSDO mis-
> behavior, the results I'm viewing are about 20 dB higher
> than the basic floor, which I am still characterizing. I
> believe that the floor is limited primarily by uncorrelated
> sampling jitter between the two 'scope channels.
>
> If there is an expression of interest in this technique, I'll
> publish a detailed description of the technique and some
> plots showing results, probably in the form of an attachment
> in pdf format.
>
> Dana
> _______________________________________________
> time-nuts mailing list -- time-***@lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.

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Richard (Rick) Karlquist
2018-10-01 21:05:35 UTC
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No one mentioned using Lissajous patterns for comparing
frequencies if the scope has an XY mode. Google Lissajous
if interested.

Rick N6RK

On 10/1/2018 11:40 AM, Bryan _ wrote:
> Interested as well
>
> -=Bryan=-
>
> ________________________________
> From: time-nuts <time-nuts-***@lists.febo.com> on behalf of Chris Burford <***@austin.rr.com>
> Sent: October 1, 2018 6:20 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Oscilloscope-based measurements of frequency stability
>
> This sounds interesting enough and I would appreciate any notes or insight on doing this. I have a PRS10 and several GPSDOs that I would like to evaluate for performance on my scope.
>
> Many thanks.
>
>
> ---- Dana Whitlow <***@gmail.com> wrote:
>> I cheered when I saw Dave B's "silly question", for
>> then I realized that I'm not the only one who likes
>> to measure things with an o'scope.
>>
>> I had purchased a GPSDO a few weeks before and
>> had been observing its behavior relative to a free-
>> running Rb by watching 10 MHz sinewaves drift with
>> respect to each other as an aid in setting the Rb's
>> frequency. However, I was seeing enough fairly
>> rapid random drift to limit the usefulness of this kind
>> of observation. It dawned on me that I was sometimes
>> seeing drifts of several ns over the course of just
>> several seconds, thus implying that sometimes the
>> relative frequency error between the two sources was
>> reaching as high as roughly 1E-9. I wanted to be able
>> to capture and plot a somewhat extended run of data
>> so I could try to understand this behavior better.
>>
>> Being TIC-less, I decided to see what I could do with
>> my o'scope, which is a Chinese-made 2-channel DSO
>> with synchronous sampling by the two channels and
>> with a respectable trace memory depth (28 MSA per
>> channel).
>>
>> I began this effort in earnest a couple of days before I
>> saw Dave's question, and have only now brought it to
>> a sufficient state of completion to feel justified in reporting
>> some results.
>>
>> I am presently able to record about 45 minute's worth of
>> data as limited by the 'scope's trace memory, but my XP
>> computer's RAM space limits me to processing only about
>> 35 minutes of that in a seamless run. Over that time
>> span I've seen a peak relative frequency discrepancy of
>> about 1.4E-9, with a handful reaching or exceeding 1E-9.
>> I've also measured average frequency differences between
>> the source's a a few parts in 10E11.
>>
>> Most of the effort went into developing a C program to do
>> the processing and then correctly scaling and displaying
>> the results in a form which I considered useful to me. This
>> processing of course had to deal with an off-frequency and
>> drifting 'scope timebase, which is *horrible* compared to the
>> quantities under measurement (as expected from the outset).
>>
>> Present indications are that at this level of GPSDO mis-
>> behavior, the results I'm viewing are about 20 dB higher
>> than the basic floor, which I am still characterizing. I
>> believe that the floor is limited primarily by uncorrelated
>> sampling jitter between the two 'scope channels.
>>
>> If there is an expression of interest in this technique, I'll
>> publish a detailed description of the technique and some
>> plots showing results, probably in the form of an attachment
>> in pdf format.
>>
>> Dana
>> _______________________________________________
>> time-nuts mailing list -- time-***@lists.febo.com
>> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
>> and follow the instructions there.
>
> _______________________________________________
> time-nuts mailing list -- time-***@lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
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> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
>

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Dana Whitlow
2018-10-01 22:54:13 UTC
Reply
Permalink
I've done the Lissajous thing, but it takes an extra bit of effort to
work out the phase angle. I've always gone back to the sliding
waveforms display for simplicity.

But I'll admit the Lissajous pattern is a lot prettier, and looks great
in Sci Fi movies.

Dana


On Mon, Oct 1, 2018 at 4:06 PM Richard (Rick) Karlquist <
***@karlquist.com> wrote:

> No one mentioned using Lissajous patterns for comparing
> frequencies if the scope has an XY mode. Google Lissajous
> if interested.
>
> Rick N6RK
>
> On 10/1/2018 11:40 AM, Bryan _ wrote:
> > Interested as well
> >
> > -=Bryan=-
> >
> > ________________________________
> > From: time-nuts <time-nuts-***@lists.febo.com> on behalf of Chris
> Burford <***@austin.rr.com>
> > Sent: October 1, 2018 6:20 AM
> > To: Discussion of precise time and frequency measurement
> > Subject: Re: [time-nuts] Oscilloscope-based measurements of frequency
> stability
> >
> > This sounds interesting enough and I would appreciate any notes or
> insight on doing this. I have a PRS10 and several GPSDOs that I would like
> to evaluate for performance on my scope.
> >
> > Many thanks.
> >
> >
> > ---- Dana Whitlow <***@gmail.com> wrote:
> >> I cheered when I saw Dave B's "silly question", for
> >> then I realized that I'm not the only one who likes
> >> to measure things with an o'scope.
> >>
> >> I had purchased a GPSDO a few weeks before and
> >> had been observing its behavior relative to a free-
> >> running Rb by watching 10 MHz sinewaves drift with
> >> respect to each other as an aid in setting the Rb's
> >> frequency. However, I was seeing enough fairly
> >> rapid random drift to limit the usefulness of this kind
> >> of observation. It dawned on me that I was sometimes
> >> seeing drifts of several ns over the course of just
> >> several seconds, thus implying that sometimes the
> >> relative frequency error between the two sources was
> >> reaching as high as roughly 1E-9. I wanted to be able
> >> to capture and plot a somewhat extended run of data
> >> so I could try to understand this behavior better.
> >>
> >> Being TIC-less, I decided to see what I could do with
> >> my o'scope, which is a Chinese-made 2-channel DSO
> >> with synchronous sampling by the two channels and
> >> with a respectable trace memory depth (28 MSA per
> >> channel).
> >>
> >> I began this effort in earnest a couple of days before I
> >> saw Dave's question, and have only now brought it to
> >> a sufficient state of completion to feel justified in reporting
> >> some results.
> >>
> >> I am presently able to record about 45 minute's worth of
> >> data as limited by the 'scope's trace memory, but my XP
> >> computer's RAM space limits me to processing only about
> >> 35 minutes of that in a seamless run. Over that time
> >> span I've seen a peak relative frequency discrepancy of
> >> about 1.4E-9, with a handful reaching or exceeding 1E-9.
> >> I've also measured average frequency differences between
> >> the source's a a few parts in 10E11.
> >>
> >> Most of the effort went into developing a C program to do
> >> the processing and then correctly scaling and displaying
> >> the results in a form which I considered useful to me. This
> >> processing of course had to deal with an off-frequency and
> >> drifting 'scope timebase, which is *horrible* compared to the
> >> quantities under measurement (as expected from the outset).
> >>
> >> Present indications are that at this level of GPSDO mis-
> >> behavior, the results I'm viewing are about 20 dB higher
> >> than the basic floor, which I am still characterizing. I
> >> believe that the floor is limited primarily by uncorrelated
> >> sampling jitter between the two 'scope channels.
> >>
> >> If there is an expression of interest in this technique, I'll
> >> publish a detailed description of the technique and some
> >> plots showing results, probably in the form of an attachment
> >> in pdf format.
> >>
> >> Dana
> >> _______________________________________________
> >> time-nuts mailing list -- time-***@lists.febo.com
> >> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> >> and follow the instructions there.
> >
> > _______________________________________________
> > time-nuts mailing list -- time-***@lists.febo.com
> > To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> > _______________________________________________
> > time-nuts mailing list -- time-***@lists.febo.com
> > To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> >
> >
>
> _______________________________________________
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> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
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>
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John Franke
2018-10-02 01:30:45 UTC
Reply
Permalink
I like the sliding waveforms and a variation used by General Radio with their circular sweep 1109A comparison oscilloscope. I built a slightly different model:

Franke, John M.: “A Circular Sweep Frequency Calibrator,” The AMSAT Journal, Volume 31, No. 4, July/August 2008, pp. 4-7.

Reprinted in Proceedings of Microwave Update 2008, Bloomington, Minnesota, October 17-18, pp. 167-170, published by the American Radio Relay League (ARRL), Inc.



> On October 1, 2018 at 6:54 PM Dana Whitlow <***@gmail.com> wrote:
>
>
> I've done the Lissajous thing, but it takes an extra bit of effort to
> work out the phase angle. I've always gone back to the sliding
> waveforms display for simplicity.
>
> But I'll admit the Lissajous pattern is a lot prettier, and looks great
> in Sci Fi movies.
>
> Dana
>
>
> On Mon, Oct 1, 2018 at 4:06 PM Richard (Rick) Karlquist <
> ***@karlquist.com> wrote:
>
> > No one mentioned using Lissajous patterns for comparing
> > frequencies if the scope has an XY mode. Google Lissajous
> > if interested.
> >
> > Rick N6RK
> >
> > On 10/1/2018 11:40 AM, Bryan _ wrote:
> > > Interested as well
> > >
> > > -=Bryan=-
> > >
> > > ________________________________
> > > From: time-nuts <time-nuts-***@lists.febo.com> on behalf of Chris
> > Burford <***@austin.rr.com>
> > > Sent: October 1, 2018 6:20 AM
> > > To: Discussion of precise time and frequency measurement
> > > Subject: Re: [time-nuts] Oscilloscope-based measurements of frequency
> > stability
> > >
> > > This sounds interesting enough and I would appreciate any notes or
> > insight on doing this. I have a PRS10 and several GPSDOs that I would like
> > to evaluate for performance on my scope.
> > >
> > > Many thanks.
> > >
> > >
> > > ---- Dana Whitlow <***@gmail.com> wrote:
> > >> I cheered when I saw Dave B's "silly question", for
> > >> then I realized that I'm not the only one who likes
> > >> to measure things with an o'scope.
> > >>
> > >> I had purchased a GPSDO a few weeks before and
> > >> had been observing its behavior relative to a free-
> > >> running Rb by watching 10 MHz sinewaves drift with
> > >> respect to each other as an aid in setting the Rb's
> > >> frequency. However, I was seeing enough fairly
> > >> rapid random drift to limit the usefulness of this kind
> > >> of observation. It dawned on me that I was sometimes
> > >> seeing drifts of several ns over the course of just
> > >> several seconds, thus implying that sometimes the
> > >> relative frequency error between the two sources was
> > >> reaching as high as roughly 1E-9. I wanted to be able
> > >> to capture and plot a somewhat extended run of data
> > >> so I could try to understand this behavior better.
> > >>
> > >> Being TIC-less, I decided to see what I could do with
> > >> my o'scope, which is a Chinese-made 2-channel DSO
> > >> with synchronous sampling by the two channels and
> > >> with a respectable trace memory depth (28 MSA per
> > >> channel).
> > >>
> > >> I began this effort in earnest a couple of days before I
> > >> saw Dave's question, and have only now brought it to
> > >> a sufficient state of completion to feel justified in reporting
> > >> some results.
> > >>
> > >> I am presently able to record about 45 minute's worth of
> > >> data as limited by the 'scope's trace memory, but my XP
> > >> computer's RAM space limits me to processing only about
> > >> 35 minutes of that in a seamless run. Over that time
> > >> span I've seen a peak relative frequency discrepancy of
> > >> about 1.4E-9, with a handful reaching or exceeding 1E-9.
> > >> I've also measured average frequency differences between
> > >> the source's a a few parts in 10E11.
> > >>
> > >> Most of the effort went into developing a C program to do
> > >> the processing and then correctly scaling and displaying
> > >> the results in a form which I considered useful to me. This
> > >> processing of course had to deal with an off-frequency and
> > >> drifting 'scope timebase, which is *horrible* compared to the
> > >> quantities under measurement (as expected from the outset).
> > >>
> > >> Present indications are that at this level of GPSDO mis-
> > >> behavior, the results I'm viewing are about 20 dB higher
> > >> than the basic floor, which I am still characterizing. I
> > >> believe that the floor is limited primarily by uncorrelated
> > >> sampling jitter between the two 'scope channels.
> > >>
> > >> If there is an expression of interest in this technique, I'll
> > >> publish a detailed description of the technique and some
> > >> plots showing results, probably in the form of an attachment
> > >> in pdf format.
> > >>
> > >> Dana
> > >> _______________________________________________
> > >> time-nuts mailing list -- time-***@lists.febo.com
> > >> To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > >> and follow the instructions there.
> > >
> > > _______________________________________________
> > > time-nuts mailing list -- time-***@lists.febo.com
> > > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > > and follow the instructions there.
> > > _______________________________________________
> > > time-nuts mailing list -- time-***@lists.febo.com
> > > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > > and follow the instructions there.
> > >
> > >
> >
> > _______________________________________________
> > time-nuts mailing list -- time-***@lists.febo.com
> > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> >
> _______________________________________________
> time-nuts mailing list -- time-***@lists.febo.com
> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.

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paul swed
2018-10-02 16:37:48 UTC
Reply
Permalink
I barely remember that article but recall it seemed like a very nice
approach.
Regards
Paul
WB8TSL

On Mon, Oct 1, 2018 at 9:32 PM John Franke <***@cox.net> wrote:

> I like the sliding waveforms and a variation used by General Radio with
> their circular sweep 1109A comparison oscilloscope. I built a slightly
> different model:
>
> Franke, John M.: “A Circular Sweep Frequency Calibrator,” The AMSAT
> Journal, Volume 31, No. 4, July/August 2008, pp. 4-7.
>
> Reprinted in Proceedings of Microwave Update 2008, Bloomington, Minnesota,
> October 17-18, pp. 167-170, published by the American Radio Relay League
> (ARRL), Inc.
>
>
>
> > On October 1, 2018 at 6:54 PM Dana Whitlow <***@gmail.com>
> wrote:
> >
> >
> > I've done the Lissajous thing, but it takes an extra bit of effort to
> > work out the phase angle. I've always gone back to the sliding
> > waveforms display for simplicity.
> >
> > But I'll admit the Lissajous pattern is a lot prettier, and looks great
> > in Sci Fi movies.
> >
> > Dana
> >
> >
> > On Mon, Oct 1, 2018 at 4:06 PM Richard (Rick) Karlquist <
> > ***@karlquist.com> wrote:
> >
> > > No one mentioned using Lissajous patterns for comparing
> > > frequencies if the scope has an XY mode. Google Lissajous
> > > if interested.
> > >
> > > Rick N6RK
> > >
> > > On 10/1/2018 11:40 AM, Bryan _ wrote:
> > > > Interested as well
> > > >
> > > > -=Bryan=-
> > > >
> > > > ________________________________
> > > > From: time-nuts <time-nuts-***@lists.febo.com> on behalf of
> Chris
> > > Burford <***@austin.rr.com>
> > > > Sent: October 1, 2018 6:20 AM
> > > > To: Discussion of precise time and frequency measurement
> > > > Subject: Re: [time-nuts] Oscilloscope-based measurements of frequency
> > > stability
> > > >
> > > > This sounds interesting enough and I would appreciate any notes or
> > > insight on doing this. I have a PRS10 and several GPSDOs that I would
> like
> > > to evaluate for performance on my scope.
> > > >
> > > > Many thanks.
> > > >
> > > >
> > > > ---- Dana Whitlow <***@gmail.com> wrote:
> > > >> I cheered when I saw Dave B's "silly question", for
> > > >> then I realized that I'm not the only one who likes
> > > >> to measure things with an o'scope.
> > > >>
> > > >> I had purchased a GPSDO a few weeks before and
> > > >> had been observing its behavior relative to a free-
> > > >> running Rb by watching 10 MHz sinewaves drift with
> > > >> respect to each other as an aid in setting the Rb's
> > > >> frequency. However, I was seeing enough fairly
> > > >> rapid random drift to limit the usefulness of this kind
> > > >> of observation. It dawned on me that I was sometimes
> > > >> seeing drifts of several ns over the course of just
> > > >> several seconds, thus implying that sometimes the
> > > >> relative frequency error between the two sources was
> > > >> reaching as high as roughly 1E-9. I wanted to be able
> > > >> to capture and plot a somewhat extended run of data
> > > >> so I could try to understand this behavior better.
> > > >>
> > > >> Being TIC-less, I decided to see what I could do with
> > > >> my o'scope, which is a Chinese-made 2-channel DSO
> > > >> with synchronous sampling by the two channels and
> > > >> with a respectable trace memory depth (28 MSA per
> > > >> channel).
> > > >>
> > > >> I began this effort in earnest a couple of days before I
> > > >> saw Dave's question, and have only now brought it to
> > > >> a sufficient state of completion to feel justified in reporting
> > > >> some results.
> > > >>
> > > >> I am presently able to record about 45 minute's worth of
> > > >> data as limited by the 'scope's trace memory, but my XP
> > > >> computer's RAM space limits me to processing only about
> > > >> 35 minutes of that in a seamless run. Over that time
> > > >> span I've seen a peak relative frequency discrepancy of
> > > >> about 1.4E-9, with a handful reaching or exceeding 1E-9.
> > > >> I've also measured average frequency differences between
> > > >> the source's a a few parts in 10E11.
> > > >>
> > > >> Most of the effort went into developing a C program to do
> > > >> the processing and then correctly scaling and displaying
> > > >> the results in a form which I considered useful to me. This
> > > >> processing of course had to deal with an off-frequency and
> > > >> drifting 'scope timebase, which is *horrible* compared to the
> > > >> quantities under measurement (as expected from the outset).
> > > >>
> > > >> Present indications are that at this level of GPSDO mis-
> > > >> behavior, the results I'm viewing are about 20 dB higher
> > > >> than the basic floor, which I am still characterizing. I
> > > >> believe that the floor is limited primarily by uncorrelated
> > > >> sampling jitter between the two 'scope channels.
> > > >>
> > > >> If there is an expression of interest in this technique, I'll
> > > >> publish a detailed description of the technique and some
> > > >> plots showing results, probably in the form of an attachment
> > > >> in pdf format.
> > > >>
> > > >> Dana
> > > >> _______________________________________________
> > > >> time-nuts mailing list -- time-***@lists.febo.com
> > > >> To unsubscribe, go to
> > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > > >> and follow the instructions there.
> > > >
> > > > _______________________________________________
> > > > time-nuts mailing list -- time-***@lists.febo.com
> > > > To unsubscribe, go to
> > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > > > and follow the instructions there.
> > > > _______________________________________________
> > > > time-nuts mailing list -- time-***@lists.febo.com
> > > > To unsubscribe, go to
> > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > > > and follow the instructions there.
> > > >
> > > >
> > >
> > > _______________________________________________
> > > time-nuts mailing list -- time-***@lists.febo.com
> > > To unsubscribe, go to
> > > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > > and follow the instructions there.
> > >
> > _______________________________________________
> > time-nuts mailing list -- time-***@lists.febo.com
> > To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
>
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Ralph Devoe
2018-10-01 22:05:05 UTC
Reply
Permalink
This is just what I was trying to do with my paper on "sine-wave
fitting", which can be found at arXiv:1711.07911 . Look at the relative
phase of two frequency sources using a scope and then plot it versus time.
With a digital scope (Digilent Analog Discovery) , there's no reason to
take a screen shot, all you have to do is write the ADC outputs to files.
The paper was written for a peer-reviewed journal, so I had to write
it in a tedious style, but it's basically the same as what is suggested
here. I used a least-square fitting routine to calculate the phase
difference in the paper, but eyeballing the phases also works.
I've been measuring the drift and aging of a pair of HP 5065a's
versus a 5071a for the last ten months and have over 200 GB of data on
disk. I'm a lousy programmer but the Python analysis routine is short (
about 100 lines) and works fine.

Ralph
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Tim Shoppa
2018-10-02 17:03:24 UTC
Reply
Permalink
Dana, the short term few-ns jitter of the two phases, I think in a digital
instrument is most likely data acquisition glitches.

Even on a good old analog scope, jitter in the trigger circuit or jitter in
amplitudes (with resulting changes in harmonic content and thus the shape
of the curves) can cause the apparent zoomed in zero crossing to shift very
similarly.

In days of old the telco standards for frequency stability also included
requirements for amplitude stability noise, directly related to making
repeatable measurements using scopes. I'm gonna see if I can find some of
those. I remember some crazy looking telco standard that required measuring
amplitude noise on time scales measured in weeks.

Tim N3QE

On Mon, Oct 1, 2018 at 8:47 AM Dana Whitlow <***@gmail.com> wrote:

> I cheered when I saw Dave B's "silly question", for
> then I realized that I'm not the only one who likes
> to measure things with an o'scope.
>
> I had purchased a GPSDO a few weeks before and
> had been observing its behavior relative to a free-
> running Rb by watching 10 MHz sinewaves drift with
> respect to each other as an aid in setting the Rb's
> frequency. However, I was seeing enough fairly
> rapid random drift to limit the usefulness of this kind
> of observation. It dawned on me that I was sometimes
> seeing drifts of several ns over the course of just
> several seconds, thus implying that sometimes the
> relative frequency error between the two sources was
> reaching as high as roughly 1E-9. I wanted to be able
> to capture and plot a somewhat extended run of data
> so I could try to understand this behavior better.
>
> Being TIC-less, I decided to see what I could do with
> my o'scope, which is a Chinese-made 2-channel DSO
> with synchronous sampling by the two channels and
> with a respectable trace memory depth (28 MSA per
> channel).
>
> I began this effort in earnest a couple of days before I
> saw Dave's question, and have only now brought it to
> a sufficient state of completion to feel justified in reporting
> some results.
>
> I am presently able to record about 45 minute's worth of
> data as limited by the 'scope's trace memory, but my XP
> computer's RAM space limits me to processing only about
> 35 minutes of that in a seamless run. Over that time
> span I've seen a peak relative frequency discrepancy of
> about 1.4E-9, with a handful reaching or exceeding 1E-9.
> I've also measured average frequency differences between
> the source's a a few parts in 10E11.
>
> Most of the effort went into developing a C program to do
> the processing and then correctly scaling and displaying
> the results in a form which I considered useful to me. This
> processing of course had to deal with an off-frequency and
> drifting 'scope timebase, which is *horrible* compared to the
> quantities under measurement (as expected from the outset).
>
> Present indications are that at this level of GPSDO mis-
> behavior, the results I'm viewing are about 20 dB higher
> than the basic floor, which I am still characterizing. I
> believe that the floor is limited primarily by uncorrelated
> sampling jitter between the two 'scope channels.
>
> If there is an expression of interest in this technique, I'll
> publish a detailed description of the technique and some
> plots showing results, probably in the form of an attachment
> in pdf format.
>
> Dana
> _______________________________________________
> time-nuts mailing list -- time-***@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
_______________________________________________
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To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.
ew via time-nuts
2018-10-02 18:44:37 UTC
Reply
Permalink
We see the glitches all the time, they exist and with proper equipment are very visible. These are telecom timing devices and the way they correct the 1 pps is by changing the frequency. Even LH shows it and it is very visible when you eliminate the other traces.What we call the Tbolt 2, the nicely packaged Trimle that also was part of the fraud listing does the correction once an hour. It is exact an hour function of when you powered it up.In my case night time spikes where mostly negative Air conditioner. Recovery is a function of the accumulated error. Standing next to it in front of my 19 year old M300 it did effect the recovery  since my legs where within a foot. One picture shows the analog trace to.Original Tbolt does it constantly. We have spend a couple of years on this, hoping to optimize a clean up loop.so far no good results.Bert Kehren
In a message dated 10/2/2018 1:04:50 PM Eastern Standard Time, ***@gmail.com writes:

Dana, the short term few-ns jitter of the two phases, I think in a digital
instrument is most likely data acquisition glitches.

Even on a good old analog scope, jitter in the trigger circuit or jitter in
amplitudes (with resulting changes in harmonic content and thus the shape
of the curves) can cause the apparent zoomed in zero crossing to shift very
similarly.

In days of old the telco standards for frequency stability also included
requirements for amplitude stability noise, directly related to making
repeatable measurements using scopes. I'm gonna see if I can find some of
those. I remember some crazy looking telco standard that required measuring
amplitude noise on time scales measured in weeks.

Tim N3QE

On Mon, Oct 1, 2018 at 8:47 AM Dana Whitlow <***@gmail.com> wrote:

> I cheered when I saw Dave B's "silly question", for
> then I realized that I'm not the only one who likes
> to measure things with an o'scope.
>
> I had purchased a GPSDO a few weeks before and
> had  been observing its behavior relative to a free-
> running Rb by watching 10 MHz sinewaves drift with
> respect to each other as an aid in setting the Rb's
> frequency.  However, I was seeing enough fairly
> rapid random drift to limit the usefulness of this kind
> of observation.  It dawned on me that I was sometimes
> seeing drifts of several ns over the course of just
> several seconds, thus implying that sometimes the
> relative frequency error between the two sources was
> reaching as high as roughly 1E-9.  I wanted to be able
> to capture and plot a somewhat extended run of data
> so I could try to understand this behavior better.
>
> Being TIC-less, I decided to see what I could do with
> my o'scope, which is a Chinese-made 2-channel DSO
> with synchronous sampling by the two channels and
> with a respectable trace memory depth (28 MSA per
> channel).
>
> I began this effort  in earnest a couple of days before I
> saw Dave's question, and have only now brought it to
> a sufficient state of completion to feel justified in reporting
> some results.
>
> I am presently able to record about 45 minute's worth of
> data as limited by the 'scope's trace memory, but my XP
> computer's RAM space limits me to processing only about
> 35 minutes of that in a seamless run.  Over that time
> span I've seen a peak relative frequency discrepancy of
> about 1.4E-9, with a handful reaching or exceeding 1E-9.
> I've also measured average frequency differences between
> the source's a a few parts in 10E11.
>
> Most of the effort went into developing a C program to do
> the processing and then correctly scaling and displaying
> the results in a form which I considered useful to me.  This
> processing of course had to deal with an off-frequency and
> drifting 'scope timebase, which is *horrible* compared to the
> quantities under measurement (as expected from the outset).
>
> Present indications are that at this level of GPSDO mis-
> behavior, the results I'm viewing are about 20 dB higher
> than the basic floor, which I am still characterizing.  I
> believe that the floor is limited primarily by uncorrelated
> sampling jitter between the two 'scope channels.
>
> If there is an expression of interest in this technique, I'll
> publish a detailed description of the technique and some
> plots showing results, probably in the form of an attachment
> in pdf format.
>
> Dana
> _______________________________________________
> time-nuts mailing list -- time-***@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
_______________________________________________
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To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
and follow the instructions there.
Dana Whitlow
2018-10-02 19:28:49 UTC
Reply
Permalink
Hello Bert,

What is the cyan-colored trace seen in these screen shots? And is
"1 ppt" the same as 1E-12 (just to be sure)?

Are these from LH?

Thanks,

Dana




On Tue, Oct 2, 2018 at 1:46 PM ew via time-nuts <time-***@lists.febo.com>
wrote:

> We see the glitches all the time, they exist and with proper equipment are
> very visible. These are telecom timing devices and the way they correct the
> 1 pps is by changing the frequency. Even LH shows it and it is very visible
> when you eliminate the other traces.What we call the Tbolt 2, the nicely
> packaged Trimle that also was part of the fraud listing does the correction
> once an hour. It is exact an hour function of when you powered it up.In my
> case night time spikes where mostly negative Air conditioner. Recovery is a
> function of the accumulated error. Standing next to it in front of my 19
> year old M300 it did effect the recovery since my legs where within a
> foot. One picture shows the analog trace to.Original Tbolt does it
> constantly. We have spend a couple of years on this, hoping to optimize a
> clean up loop.so far no good results.Bert Kehren
> In a message dated 10/2/2018 1:04:50 PM Eastern Standard Time,
> ***@gmail.com writes:
>
> Dana, the short term few-ns jitter of the two phases, I think in a digital
> instrument is most likely data acquisition glitches.
>
> Even on a good old analog scope, jitter in the trigger circuit or jitter in
> amplitudes (with resulting changes in harmonic content and thus the shape
> of the curves) can cause the apparent zoomed in zero crossing to shift very
> similarly.
>
> In days of old the telco standards for frequency stability also included
> requirements for amplitude stability noise, directly related to making
> repeatable measurements using scopes. I'm gonna see if I can find some of
> those. I remember some crazy looking telco standard that required measuring
> amplitude noise on time scales measured in weeks.
>
> Tim N3QE
>
> On Mon, Oct 1, 2018 at 8:47 AM Dana Whitlow <***@gmail.com> wrote:
>
> > I cheered when I saw Dave B's "silly question", for
> > then I realized that I'm not the only one who likes
> > to measure things with an o'scope.
> >
> > I had purchased a GPSDO a few weeks before and
> > had been observing its behavior relative to a free-
> > running Rb by watching 10 MHz sinewaves drift with
> > respect to each other as an aid in setting the Rb's
> > frequency. However, I was seeing enough fairly
> > rapid random drift to limit the usefulness of this kind
> > of observation. It dawned on me that I was sometimes
> > seeing drifts of several ns over the course of just
> > several seconds, thus implying that sometimes the
> > relative frequency error between the two sources was
> > reaching as high as roughly 1E-9. I wanted to be able
> > to capture and plot a somewhat extended run of data
> > so I could try to understand this behavior better.
> >
> > Being TIC-less, I decided to see what I could do with
> > my o'scope, which is a Chinese-made 2-channel DSO
> > with synchronous sampling by the two channels and
> > with a respectable trace memory depth (28 MSA per
> > channel).
> >
> > I began this effort in earnest a couple of days before I
> > saw Dave's question, and have only now brought it to
> > a sufficient state of completion to feel justified in reporting
> > some results.
> >
> > I am presently able to record about 45 minute's worth of
> > data as limited by the 'scope's trace memory, but my XP
> > computer's RAM space limits me to processing only about
> > 35 minutes of that in a seamless run. Over that time
> > span I've seen a peak relative frequency discrepancy of
> > about 1.4E-9, with a handful reaching or exceeding 1E-9.
> > I've also measured average frequency differences between
> > the source's a a few parts in 10E11.
> >
> > Most of the effort went into developing a C program to do
> > the processing and then correctly scaling and displaying
> > the results in a form which I considered useful to me. This
> > processing of course had to deal with an off-frequency and
> > drifting 'scope timebase, which is *horrible* compared to the
> > quantities under measurement (as expected from the outset).
> >
> > Present indications are that at this level of GPSDO mis-
> > behavior, the results I'm viewing are about 20 dB higher
> > than the basic floor, which I am still characterizing. I
> > believe that the floor is limited primarily by uncorrelated
> > sampling jitter between the two 'scope channels.
> >
> > If there is an expression of interest in this technique, I'll
> > publish a detailed description of the technique and some
> > plots showing results, probably in the form of an attachment
> > in pdf format.
> >
> > Dana
> > _______________________________________________
> > time-nuts mailing list -- time-***@lists.febo.com
> > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> >
> _______________________________________________
> time-nuts mailing list -- time-***@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
> _______________________________________________
> time-nuts mailing list -- time-***@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
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Bryan _
2018-10-02 19:36:16 UTC
Reply
Permalink
The number of satellites. Yes, from LH

-=Bryan=-

________________________________
From: time-nuts <time-nuts-***@lists.febo.com> on behalf of Dana Whitlow <***@gmail.com>
Sent: October 2, 2018 12:28 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Oscilloscope-based measurements of frequency stability

Hello Bert,

What is the cyan-colored trace seen in these screen shots? And is
"1 ppt" the same as 1E-12 (just to be sure)?

Are these from LH?

Thanks,

Dana




On Tue, Oct 2, 2018 at 1:46 PM ew via time-nuts <time-***@lists.febo.com>
wrote:

> We see the glitches all the time, they exist and with proper equipment are
> very visible. These are telecom timing devices and the way they correct the
> 1 pps is by changing the frequency. Even LH shows it and it is very visible
> when you eliminate the other traces.What we call the Tbolt 2, the nicely
> packaged Trimle that also was part of the fraud listing does the correction
> once an hour. It is exact an hour function of when you powered it up.In my
> case night time spikes where mostly negative Air conditioner. Recovery is a
> function of the accumulated error. Standing next to it in front of my 19
> year old M300 it did effect the recovery since my legs where within a
> foot. One picture shows the analog trace to.Original Tbolt does it
> constantly. We have spend a couple of years on this, hoping to optimize a
> clean up loop.so far no good results.Bert Kehren
> In a message dated 10/2/2018 1:04:50 PM Eastern Standard Time,
> ***@gmail.com writes:
>
> Dana, the short term few-ns jitter of the two phases, I think in a digital
> instrument is most likely data acquisition glitches.
>
> Even on a good old analog scope, jitter in the trigger circuit or jitter in
> amplitudes (with resulting changes in harmonic content and thus the shape
> of the curves) can cause the apparent zoomed in zero crossing to shift very
> similarly.
>
> In days of old the telco standards for frequency stability also included
> requirements for amplitude stability noise, directly related to making
> repeatable measurements using scopes. I'm gonna see if I can find some of
> those. I remember some crazy looking telco standard that required measuring
> amplitude noise on time scales measured in weeks.
>
> Tim N3QE
>
> On Mon, Oct 1, 2018 at 8:47 AM Dana Whitlow <***@gmail.com> wrote:
>
> > I cheered when I saw Dave B's "silly question", for
> > then I realized that I'm not the only one who likes
> > to measure things with an o'scope.
> >
> > I had purchased a GPSDO a few weeks before and
> > had been observing its behavior relative to a free-
> > running Rb by watching 10 MHz sinewaves drift with
> > respect to each other as an aid in setting the Rb's
> > frequency. However, I was seeing enough fairly
> > rapid random drift to limit the usefulness of this kind
> > of observation. It dawned on me that I was sometimes
> > seeing drifts of several ns over the course of just
> > several seconds, thus implying that sometimes the
> > relative frequency error between the two sources was
> > reaching as high as roughly 1E-9. I wanted to be able
> > to capture and plot a somewhat extended run of data
> > so I could try to understand this behavior better.
> >
> > Being TIC-less, I decided to see what I could do with
> > my o'scope, which is a Chinese-made 2-channel DSO
> > with synchronous sampling by the two channels and
> > with a respectable trace memory depth (28 MSA per
> > channel).
> >
> > I began this effort in earnest a couple of days before I
> > saw Dave's question, and have only now brought it to
> > a sufficient state of completion to feel justified in reporting
> > some results.
> >
> > I am presently able to record about 45 minute's worth of
> > data as limited by the 'scope's trace memory, but my XP
> > computer's RAM space limits me to processing only about
> > 35 minutes of that in a seamless run. Over that time
> > span I've seen a peak relative frequency discrepancy of
> > about 1.4E-9, with a handful reaching or exceeding 1E-9.
> > I've also measured average frequency differences between
> > the source's a a few parts in 10E11.
> >
> > Most of the effort went into developing a C program to do
> > the processing and then correctly scaling and displaying
> > the results in a form which I considered useful to me. This
> > processing of course had to deal with an off-frequency and
> > drifting 'scope timebase, which is *horrible* compared to the
> > quantities under measurement (as expected from the outset).
> >
> > Present indications are that at this level of GPSDO mis-
> > behavior, the results I'm viewing are about 20 dB higher
> > than the basic floor, which I am still characterizing. I
> > believe that the floor is limited primarily by uncorrelated
> > sampling jitter between the two 'scope channels.
> >
> > If there is an expression of interest in this technique, I'll
> > publish a detailed description of the technique and some
> > plots showing results, probably in the form of an attachment
> > in pdf format.
> >
> > Dana
> > _______________________________________________
> > time-nuts mailing list -- time-***@lists.febo.com
> > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> >
> _______________________________________________
> time-nuts mailing list -- time-***@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
> _______________________________________________
> time-nuts mailing list -- time-***@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
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ew via time-nuts
2018-10-02 19:38:20 UTC
Reply
Permalink
yes and 1 ppt is 1 E-12
In a message dated 10/2/2018 3:30:31 PM Eastern Standard Time, ***@gmail.com writes:

Hello Bert,

What is the cyan-colored trace seen in these screen shots?  And is
"1 ppt" the same as 1E-12 (just to be sure)?

Are these from LH?

Thanks,

Dana




On Tue, Oct 2, 2018 at 1:46 PM ew via time-nuts <time-***@lists.febo.com>
wrote:

> We see the glitches all the time, they exist and with proper equipment are
> very visible. These are telecom timing devices and the way they correct the
> 1 pps is by changing the frequency. Even LH shows it and it is very visible
> when you eliminate the other traces.What we call the Tbolt 2, the nicely
> packaged Trimle that also was part of the fraud listing does the correction
> once an hour. It is exact an hour function of when you powered it up.In my
> case night time spikes where mostly negative Air conditioner. Recovery is a
> function of the accumulated error. Standing next to it in front of my 19
> year old M300 it did effect the recovery  since my legs where within a
> foot. One picture shows the analog trace to.Original Tbolt does it
> constantly. We have spend a couple of years on this, hoping to optimize a
> clean up loop.so far no good results.Bert Kehren
> In a message dated 10/2/2018 1:04:50 PM Eastern Standard Time,
> ***@gmail.com writes:
>
> Dana, the short term few-ns jitter of the two phases, I think in a digital
> instrument is most likely data acquisition glitches.
>
> Even on a good old analog scope, jitter in the trigger circuit or jitter in
> amplitudes (with resulting changes in harmonic content and thus the shape
> of the curves) can cause the apparent zoomed in zero crossing to shift very
> similarly.
>
> In days of old the telco standards for frequency stability also included
> requirements for amplitude stability noise, directly related to making
> repeatable measurements using scopes. I'm gonna see if I can find some of
> those. I remember some crazy looking telco standard that required measuring
> amplitude noise on time scales measured in weeks.
>
> Tim N3QE
>
> On Mon, Oct 1, 2018 at 8:47 AM Dana Whitlow <***@gmail.com> wrote:
>
> > I cheered when I saw Dave B's "silly question", for
> > then I realized that I'm not the only one who likes
> > to measure things with an o'scope.
> >
> > I had purchased a GPSDO a few weeks before and
> > had  been observing its behavior relative to a free-
> > running Rb by watching 10 MHz sinewaves drift with
> > respect to each other as an aid in setting the Rb's
> > frequency.  However, I was seeing enough fairly
> > rapid random drift to limit the usefulness of this kind
> > of observation.  It dawned on me that I was sometimes
> > seeing drifts of several ns over the course of just
> > several seconds, thus implying that sometimes the
> > relative frequency error between the two sources was
> > reaching as high as roughly 1E-9.  I wanted to be able
> > to capture and plot a somewhat extended run of data
> > so I could try to understand this behavior better.
> >
> > Being TIC-less, I decided to see what I could do with
> > my o'scope, which is a Chinese-made 2-channel DSO
> > with synchronous sampling by the two channels and
> > with a respectable trace memory depth (28 MSA per
> > channel).
> >
> > I began this effort  in earnest a couple of days before I
> > saw Dave's question, and have only now brought it to
> > a sufficient state of completion to feel justified in reporting
> > some results.
> >
> > I am presently able to record about 45 minute's worth of
> > data as limited by the 'scope's trace memory, but my XP
> > computer's RAM space limits me to processing only about
> > 35 minutes of that in a seamless run.  Over that time
> > span I've seen a peak relative frequency discrepancy of
> > about 1.4E-9, with a handful reaching or exceeding 1E-9.
> > I've also measured average frequency differences between
> > the source's a a few parts in 10E11.
> >
> > Most of the effort went into developing a C program to do
> > the processing and then correctly scaling and displaying
> > the results in a form which I considered useful to me.  This
> > processing of course had to deal with an off-frequency and
> > drifting 'scope timebase, which is *horrible* compared to the
> > quantities under measurement (as expected from the outset).
> >
> > Present indications are that at this level of GPSDO mis-
> > behavior, the results I'm viewing are about 20 dB higher
> > than the basic floor, which I am still characterizing.  I
> > believe that the floor is limited primarily by uncorrelated
> > sampling jitter between the two 'scope channels.
> >
> > If there is an expression of interest in this technique, I'll
> > publish a detailed description of the technique and some
> > plots showing results, probably in the form of an attachment
> > in pdf format.
> >
> > Dana
> > _______________________________________________
> > time-nuts mailing list -- time-***@lists.febo.com
> > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> >
> _______________________________________________
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> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
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> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
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ew via time-nuts
2018-10-02 19:36:46 UTC
Reply
Permalink
Yes they are LH and the blue? is satelite
In a message dated 10/2/2018 3:30:31 PM Eastern Standard Time, ***@gmail.com writes:

Hello Bert,

What is the cyan-colored trace seen in these screen shots?  And is
"1 ppt" the same as 1E-12 (just to be sure)?

Are these from LH?

Thanks,

Dana




On Tue, Oct 2, 2018 at 1:46 PM ew via time-nuts <time-***@lists.febo.com>
wrote:

> We see the glitches all the time, they exist and with proper equipment are
> very visible. These are telecom timing devices and the way they correct the
> 1 pps is by changing the frequency. Even LH shows it and it is very visible
> when you eliminate the other traces.What we call the Tbolt 2, the nicely
> packaged Trimle that also was part of the fraud listing does the correction
> once an hour. It is exact an hour function of when you powered it up.In my
> case night time spikes where mostly negative Air conditioner. Recovery is a
> function of the accumulated error. Standing next to it in front of my 19
> year old M300 it did effect the recovery  since my legs where within a
> foot. One picture shows the analog trace to.Original Tbolt does it
> constantly. We have spend a couple of years on this, hoping to optimize a
> clean up loop.so far no good results.Bert Kehren
> In a message dated 10/2/2018 1:04:50 PM Eastern Standard Time,
> ***@gmail.com writes:
>
> Dana, the short term few-ns jitter of the two phases, I think in a digital
> instrument is most likely data acquisition glitches.
>
> Even on a good old analog scope, jitter in the trigger circuit or jitter in
> amplitudes (with resulting changes in harmonic content and thus the shape
> of the curves) can cause the apparent zoomed in zero crossing to shift very
> similarly.
>
> In days of old the telco standards for frequency stability also included
> requirements for amplitude stability noise, directly related to making
> repeatable measurements using scopes. I'm gonna see if I can find some of
> those. I remember some crazy looking telco standard that required measuring
> amplitude noise on time scales measured in weeks.
>
> Tim N3QE
>
> On Mon, Oct 1, 2018 at 8:47 AM Dana Whitlow <***@gmail.com> wrote:
>
> > I cheered when I saw Dave B's "silly question", for
> > then I realized that I'm not the only one who likes
> > to measure things with an o'scope.
> >
> > I had purchased a GPSDO a few weeks before and
> > had  been observing its behavior relative to a free-
> > running Rb by watching 10 MHz sinewaves drift with
> > respect to each other as an aid in setting the Rb's
> > frequency.  However, I was seeing enough fairly
> > rapid random drift to limit the usefulness of this kind
> > of observation.  It dawned on me that I was sometimes
> > seeing drifts of several ns over the course of just
> > several seconds, thus implying that sometimes the
> > relative frequency error between the two sources was
> > reaching as high as roughly 1E-9.  I wanted to be able
> > to capture and plot a somewhat extended run of data
> > so I could try to understand this behavior better.
> >
> > Being TIC-less, I decided to see what I could do with
> > my o'scope, which is a Chinese-made 2-channel DSO
> > with synchronous sampling by the two channels and
> > with a respectable trace memory depth (28 MSA per
> > channel).
> >
> > I began this effort  in earnest a couple of days before I
> > saw Dave's question, and have only now brought it to
> > a sufficient state of completion to feel justified in reporting
> > some results.
> >
> > I am presently able to record about 45 minute's worth of
> > data as limited by the 'scope's trace memory, but my XP
> > computer's RAM space limits me to processing only about
> > 35 minutes of that in a seamless run.  Over that time
> > span I've seen a peak relative frequency discrepancy of
> > about 1.4E-9, with a handful reaching or exceeding 1E-9.
> > I've also measured average frequency differences between
> > the source's a a few parts in 10E11.
> >
> > Most of the effort went into developing a C program to do
> > the processing and then correctly scaling and displaying
> > the results in a form which I considered useful to me.  This
> > processing of course had to deal with an off-frequency and
> > drifting 'scope timebase, which is *horrible* compared to the
> > quantities under measurement (as expected from the outset).
> >
> > Present indications are that at this level of GPSDO mis-
> > behavior, the results I'm viewing are about 20 dB higher
> > than the basic floor, which I am still characterizing.  I
> > believe that the floor is limited primarily by uncorrelated
> > sampling jitter between the two 'scope channels.
> >
> > If there is an expression of interest in this technique, I'll
> > publish a detailed description of the technique and some
> > plots showing results, probably in the form of an attachment
> > in pdf format.
> >
> > Dana
> > _______________________________________________
> > time-nuts mailing list -- time-***@lists.febo.com
> > To unsubscribe, go to
> > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> > and follow the instructions there.
> >
> _______________________________________________
> time-nuts mailing list -- time-***@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
> _______________________________________________
> time-nuts mailing list -- time-***@lists.febo.com
> To unsubscribe, go to
> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com
> and follow the instructions there.
>
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and follow the in
Dana Whitlow
2018-10-07 21:03:30 UTC
Reply
Permalink
Hello,

Here is the promised discussion (from about a week ago) of my scheme for
using a DSO to capture the information needed to produce detailed plots of
phase and frequency modulations of a noisy source under test.

Alas, the method is apparently inadequate for characterizing a source as
quiet as I feel I need for some future experiments, but I felt that the
method
itself (if implemented with better equipment) could be of interest as an
alternative to TIC-based methods. The text file also includes some
discussion
of a different method that I feel will probably be better suited to my
future
needs.

Look for two attached files: a text file bearing the method's description
and
discussion, and a pdf file (~102 kB) showing a sample plot of relative phase
and frequency versus time.

Dana Whitlow K8YUM
10/7/2018

On Mon, Oct 1, 2018 at 7:45 AM Dana Whitlow <***@gmail.com> wrote:

> I cheered when I saw Dave B's "silly question", for
> then I realized that I'm not the only one who likes
> to measure things with an o'scope.
>
> I had purchased a GPSDO a few weeks before and
> had been observing its behavior relative to a free-
> running Rb by watching 10 MHz sinewaves drift with
> respect to each other as an aid in setting the Rb's
> frequency. However, I was seeing enough fairly
> rapid random drift to limit the usefulness of this kind
> of observation. It dawned on me that I was sometimes
> seeing drifts of several ns over the course of just
> several seconds, thus implying that sometimes the
> relative frequency error between the two sources was
> reaching as high as roughly 1E-9. I wanted to be able
> to capture and plot a somewhat extended run of data
> so I could try to understand this behavior better.
>
> Being TIC-less, I decided to see what I could do with
> my o'scope, which is a Chinese-made 2-channel DSO
> with synchronous sampling by the two channels and
> with a respectable trace memory depth (28 MSA per
> channel).
>
> I began this effort in earnest a couple of days before I
> saw Dave's question, and have only now brought it to
> a sufficient state of completion to feel justified in reporting
> some results.
>
> I am presently able to record about 45 minute's worth of
> data as limited by the 'scope's trace memory, but my XP
> computer's RAM space limits me to processing only about
> 35 minutes of that in a seamless run. Over that time
> span I've seen a peak relative frequency discrepancy of
> about 1.4E-9, with a handful reaching or exceeding 1E-9.
> I've also measured average frequency differences between
> the source's a a few parts in 10E11.
>
> Most of the effort went into developing a C program to do
> the processing and then correctly scaling and displaying
> the results in a form which I considered useful to me. This
> processing of course had to deal with an off-frequency and
> drifting 'scope timebase, which is *horrible* compared to the
> quantities under measurement (as expected from the outset).
>
> Present indications are that at this level of GPSDO mis-
> behavior, the results I'm viewing are about 20 dB higher
> than the basic floor, which I am still characterizing. I
> believe that the floor is limited primarily by uncorrelated
> sampling jitter between the two 'scope channels.
>
> If there is an expression of interest in this technique, I'll
> publish a detailed description of the technique and some
> plots showing results, probably in the form of an attachment
> in pdf format.
>
> Dana
>
>
Christoph Kopetzky
2018-10-10 13:50:51 UTC
Reply
Permalink
Hello Dana,

thank you for your detailied description. I will try this out in the
next days.
Scopes became a right normal permanent instrument in the electronics lab
of time-nuts
like a multimeter for the electrician.
Before I connect a counter onto a signalsource which I want to
characterize I am first looking with the scope on it.
A few month ago I built an dual card for a quarz ofen oscillator from Eb...
After measuring the output frequency on both channels I was wondering
why this one gave absolute nonsense instead of the expected 10 MHz count.
After some experiments I hooked on the scope and looked on the signaltrace.
Instead of a pure sinusoidal signal which I assumed the scope showed a
totally
distorted multisinusoidal signal which had no definitive wavelength but
a overlapped
form with several peaks like a modulated sinusoidal carrier wave mixed
with with another sinusoidal signal with a frequency relation of 10 : 1.
After rerouting some circuit tracks and optimizing the shielding the
effect was gone.
So this was the reason why my scope became an every time instrument in
my lab.

--

mit freundlichen Gruessen - with best Regards

Christoph Kopetzky


Am 07.10.2018 um 23:03 schrieb Dana Whitlow:
> Hello,
>
> Here is the promised discussion (from about a week ago) of my scheme for
> using a DSO to capture the information needed to produce detailed plots of
> phase and frequency modulations of a noisy source under test.
>
> Alas, the method is apparently inadequate for characterizing a source as
> quiet as I feel I need for some future experiments, but I felt that the
> method
> itself (if implemented with better equipment) could be of interest as an
> alternative to TIC-based methods. The text file also includes some
> discussion
> of a different method that I feel will probably be better suited to my
> future
> needs.
>

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