Re: [time-nuts] General questions about making measurements with time interval counter.

[Bob Camp]

Hi


> On Jan 12, 2017, at 4:06 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> Hi Bob,
> OK, like Bugs Bunny, I'll venture out on the limb, cut the limb, and see 
> whether I fall or the tree falls:
> Wouldn't it take 1801 samples to get 18 seconds at 100S tau?  Maybe I didn't 
> state that properly, but I think you get my meaning.  Also, I've never 
> actually taken the time to look at the formula or the code to see how the 
> ADEV is calculated.  But doesn't it use a sliding boxcar type of calculation? 
>  

Nope, the proper approach for ADEV is to decimate the sample set.

Bob

> Or is that some other *DEV?  My point is that for 1801 seconds, aren't there 
> a lot more than 18 samples put in the 100S bin?  And I've probably stated 
> that incorrectly, too.  
> 
> Bob
> 
> 
>  From: Bob Camp <kb...@n1k.org>
> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
> measurement <time-nuts@febo.com> 
> Sent: Thursday, January 12, 2017 2:38 PM
> Subject: Re: [time-nuts] General questions about making measurements with 
> time interval counter.
> 
> Hi
> 
> Keep in mind that when you do 1800 samples at 1 second, that data will only 
> meet the 
> 100 sample requirement out to tau = 18 seconds. Past that you are in the 
> “under 100 samples
> region”.
> 
> Bob
> 
>> On Jan 12, 2017, at 2:32 PM, Bob Stewart <b...@evoria.net> wrote:
>> 
>> Hi Bob,
>> OK, thanks for explaining.  When you and others use highly technical terms 
>> like "small number of samples" it's not always clear to me what you mean.  
>> =)  Ten samples?  That's not enough for anything.  Normally I run at least 
>> 1800 samples; at least if I plan to share them with someone.
>> 
>> Bob -
>> AE6RV.com
>> 
>> GFS GPSDO list:
>> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>> 
>>   From: Bob Camp <kb...@n1k.org>
>> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
>> measurement <time-nuts@febo.com> 
>> Sent: Thursday, January 12, 2017 1:03 PM
>> Subject: Re: [time-nuts] General questions about making measurements with 
>> time interval counter.
>> 
>> Hi
>> 
>> It varies from 5370 to 5370. You see a lot of plots that run out to 10 
>> samples or less. Anything below 100 samples
>> is risky in some senses.
>> 
>> Bob
>> 
>>> On Jan 12, 2017, at 12:25 PM, Bob Stewart <b...@evoria.net> wrote:
>>> 
>>> Hi Bob,
>>> OK, what's a small number of data points?  Attached is a screencap of 
>>> captures for 25, 50, 75, 100, and 150 seconds.  Yeah, at 25 seconds, the 1S 
>>> tau is up at 4.56E-11, but it falls pretty quickly.  I will mention that 
>>> this particular 5370 is much better than my other one.  So, maybe this one 
>>> is an exceptional example?
>>> 
>>> Just for grins, I also included a screencap of the phase points.
>>> 
>>> Bob ---------
>>> AE6RV.com
>>> 
>>> GFS GPSDO list:
>>> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>>> 
>>>   From: Bob Camp <kb...@n1k.org>
>>> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
>>> measurement <time-nuts@febo.com> 
>>> Sent: Thursday, January 12, 2017 11:04 AM
>>> Subject: Re: [time-nuts] General questions about making measurements with 
>>> time interval counter.
>>> 
>>> Hi
>>> 
>>> There is a big difference between RMS and single shot. Single shot, the 
>>> 5370 is a very different beast. 
>>> That’s not a big deal when you have a few thousand readings and it all 
>>> averages down. Unfortunately 
>>> we all love to do runs with a very small number of points and then draw 
>>> conclusions from them. As the 
>>> sample size goes down, you no longer have a 2 to 4 x 10^-11 beast, it’s 
>>> more like 5X that.
>>> 
>>> Bob
>>> 
>>> 
>>>> On Jan 12, 2017, at 11:31 AM, Bob Stewart <b...@evoria.net> wrote:
>>>> 
>>>> Hi Bob,
>>>> Normally I see somewhere between 2E-11 and 4E-11 at 1S tau on my 5370A, as 
>>>> in the blue trace on the attached plot.  Am I misunderstanding your 
>>>> meaning?  Granted, I am clocking the 5370A with a GPSDO, but I believe I 
>>>> see about the same thing with the HP10811.  This test was 1PPS vs 1PPS 

Re: [time-nuts] General questions about making measurements with time interval counter.

[Bob Stewart]

Hi Tom,
I seem to remember a discussion of overlapping vs contiguous ADEV from some 
time ago.  So, I did a websearch, and this showed up from your site.  NB this 
is a link to a pdf file.
leapsecond.com/hsn2006/pendulum-tides-ch2.pdf
Bob


  From: Tom Van Baak <t...@leapsecond.com>
 To: Discussion of precise time and frequency measurement <time-nuts@febo.com> 
 Sent: Thursday, January 12, 2017 5:22 PM
 Subject: Re: [time-nuts] General questions about making measurements with time 
interval counter.
   
Bob,

The minimal C code for (back-to-back or overlapping) ADEV is:

    stride = overlap ? 1 : tau;
    for (sum = n = i = 0; (i + 2*tau) < count; i += stride, n += 1)
        sum += pow(phase[i + 2*tau] - 2 * phase[i + tau] + phase[i], 2);
    return sqrt(sum / 2 / n) / tau;

See adev_lib.c under www.LeapSecond.com/tools/ and also adev0.c adev4.c adev5.c
The latter two display the number of terms used in the calculation, which 
partly addresses your question.

/tvb

- Original Message - 
From: "Scott Stobbe" <scott.j.sto...@gmail.com>
To: "Bob Stewart" <b...@evoria.net>; "Discussion of precise time and frequency 
measurement" <time-nuts@febo.com>
Sent: Thursday, January 12, 2017 2:36 PM
Subject: Re: [time-nuts] General questions about making measurements with time 
interval counter.


The pesudo code for the Adev is quite easy to interpret.

For a frequency record of N samples

For each tau=M samples
    Reshape(N/M,M)
    Mean
    Diff
    Rms
End

On Thu, Jan 12, 2017 at 4:11 PM Bob Stewart <b...@evoria.net> wrote:

> Hi Bob,
>
> OK, like Bugs Bunny, I'll venture out on the limb, cut the limb, and see
> whether I fall or the tree falls:
>
> Wouldn't it take 1801 samples to get 18 seconds at 100S tau?  Maybe I
> didn't state that properly, but I think you get my meaning.  Also, I've
> never actually taken the time to look at the formula or the code to see how
> the ADEV is calculated.  But doesn't it use a sliding boxcar type of
> calculation?  Or is that some other *DEV?  My point is that for 1801
> seconds, aren't there a lot more than 18 samples put in the 100S bin?  And
> I've probably stated that incorrectly, too.
>
>
>
> Bob
>
>
>
>
>
>      From: Bob Camp <kb...@n1k.org>
>
>  To: Bob Stewart <b...@evoria.net>; Discussion of precise time and
> frequency measurement <time-nuts@febo.com>
>
>  Sent: Thursday, January 12, 2017 2:38 PM
>
>  Subject: Re: [time-nuts] General questions about making measurements with
> time interval counter.
>
>
>
> Hi
>
>
>
> Keep in mind that when you do 1800 samples at 1 second, that data will
> only meet the
>
> 100 sample requirement out to tau = 18 seconds. Past that you are in the
> “under 100 samples
>
> region”.
>
>
>
> Bob
>
>
>
> > On Jan 12, 2017, at 2:32 PM, Bob Stewart <b...@evoria.net> wrote:
>
> >
>
> > Hi Bob,
>
> > OK, thanks for explaining.  When you and others use highly technical
> terms like "small number of samples" it's not always clear to me what you
> mean.  =)  Ten samples?  That's not enough for anything.  Normally I run at
> least 1800 samples; at least if I plan to share them with someone.
>
> >
>
> > Bob -
>
> > AE6RV.com
>
> >
>
> > GFS GPSDO list:
>
> > groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>
> >
>
> >      From: Bob Camp <kb...@n1k.org>
>
> > To: Bob Stewart <b...@evoria.net>; Discussion of precise time and
> frequency measurement <time-nuts@febo.com>
>
> > Sent: Thursday, January 12, 2017 1:03 PM
>
> > Subject: Re: [time-nuts] General questions about making measurements
> with time interval counter.
>
> >
>
> > Hi
>
> >
>
> > It varies from 5370 to 5370. You see a lot of plots that run out to 10
> samples or less. Anything below 100 samples
>
> > is risky in some senses.
>
> >
>
> > Bob
>
> >
>
> >> On Jan 12, 2017, at 12:25 PM, Bob Stewart <b...@evoria.net> wrote:
>
> >>
>
> >> Hi Bob,
>
> >> OK, what's a small number of data points?  Attached is a screencap of
> captures for 25, 50, 75, 100, and 150 seconds.  Yeah, at 25 seconds, the 1S
> tau is up at 4.56E-11, but it falls pretty quickly.  I will mention that
> this particular 5370 is much better than my other one.  So, maybe this one
> is an exceptional example?
>
> >>
>
> >> Just for grins, I also included a screencap of the phase points.
>
> >>
>
> >> Bob ---

Re: [time-nuts] General questions about making measurements with time interval counter.

[Tom Van Baak]

Bob,

The minimal C code for (back-to-back or overlapping) ADEV is:

stride = overlap ? 1 : tau;
for (sum = n = i = 0; (i + 2*tau) < count; i += stride, n += 1)
sum += pow(phase[i + 2*tau] - 2 * phase[i + tau] + phase[i], 2);
return sqrt(sum / 2 / n) / tau;

See adev_lib.c under www.LeapSecond.com/tools/ and also adev0.c adev4.c adev5.c
The latter two display the number of terms used in the calculation, which 
partly addresses your question.

/tvb

- Original Message - 
From: "Scott Stobbe" <scott.j.sto...@gmail.com>
To: "Bob Stewart" <b...@evoria.net>; "Discussion of precise time and frequency 
measurement" <time-nuts@febo.com>
Sent: Thursday, January 12, 2017 2:36 PM
Subject: Re: [time-nuts] General questions about making measurements with time 
interval counter.


The pesudo code for the Adev is quite easy to interpret.

For a frequency record of N samples

For each tau=M samples
Reshape(N/M,M)
Mean
Diff
Rms
End

On Thu, Jan 12, 2017 at 4:11 PM Bob Stewart <b...@evoria.net> wrote:

> Hi Bob,
>
> OK, like Bugs Bunny, I'll venture out on the limb, cut the limb, and see
> whether I fall or the tree falls:
>
> Wouldn't it take 1801 samples to get 18 seconds at 100S tau?  Maybe I
> didn't state that properly, but I think you get my meaning.  Also, I've
> never actually taken the time to look at the formula or the code to see how
> the ADEV is calculated.  But doesn't it use a sliding boxcar type of
> calculation?  Or is that some other *DEV?  My point is that for 1801
> seconds, aren't there a lot more than 18 samples put in the 100S bin?  And
> I've probably stated that incorrectly, too.
>
>
>
> Bob
>
>
>
>
>
>   From: Bob Camp <kb...@n1k.org>
>
>  To: Bob Stewart <b...@evoria.net>; Discussion of precise time and
> frequency measurement <time-nuts@febo.com>
>
>  Sent: Thursday, January 12, 2017 2:38 PM
>
>  Subject: Re: [time-nuts] General questions about making measurements with
> time interval counter.
>
>
>
> Hi
>
>
>
> Keep in mind that when you do 1800 samples at 1 second, that data will
> only meet the
>
> 100 sample requirement out to tau = 18 seconds. Past that you are in the
> “under 100 samples
>
> region”.
>
>
>
> Bob
>
>
>
> > On Jan 12, 2017, at 2:32 PM, Bob Stewart <b...@evoria.net> wrote:
>
> >
>
> > Hi Bob,
>
> > OK, thanks for explaining.  When you and others use highly technical
> terms like "small number of samples" it's not always clear to me what you
> mean.  =)  Ten samples?  That's not enough for anything.  Normally I run at
> least 1800 samples; at least if I plan to share them with someone.
>
> >
>
> > Bob -
>
> > AE6RV.com
>
> >
>
> > GFS GPSDO list:
>
> > groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>
> >
>
> >  From: Bob Camp <kb...@n1k.org>
>
> > To: Bob Stewart <b...@evoria.net>; Discussion of precise time and
> frequency measurement <time-nuts@febo.com>
>
> > Sent: Thursday, January 12, 2017 1:03 PM
>
> > Subject: Re: [time-nuts] General questions about making measurements
> with time interval counter.
>
> >
>
> > Hi
>
> >
>
> > It varies from 5370 to 5370. You see a lot of plots that run out to 10
> samples or less. Anything below 100 samples
>
> > is risky in some senses.
>
> >
>
> > Bob
>
> >
>
> >> On Jan 12, 2017, at 12:25 PM, Bob Stewart <b...@evoria.net> wrote:
>
> >>
>
> >> Hi Bob,
>
> >> OK, what's a small number of data points?  Attached is a screencap of
> captures for 25, 50, 75, 100, and 150 seconds.  Yeah, at 25 seconds, the 1S
> tau is up at 4.56E-11, but it falls pretty quickly.  I will mention that
> this particular 5370 is much better than my other one.  So, maybe this one
> is an exceptional example?
>
> >>
>
> >> Just for grins, I also included a screencap of the phase points.
>
> >>
>
> >> Bob -
>
> >> AE6RV.com
>
> >>
>
> >> GFS GPSDO list:
>
> >> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>
> >>
>
> >>  From: Bob Camp <kb...@n1k.org>
>
> >> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and
> frequency measurement <time-nuts@febo.com>
>
> >> Sent: Thursday, January 12, 2017 11:04 AM
>
> >> Subject: Re: [time-nuts] General questions about making 

Re: [time-nuts] General questions about making measurements with time interval counter.

[Scott Stobbe]

The pesudo code for the Adev is quite easy to interpret.

For a frequency record of N samples

For each tau=M samples
Reshape(N/M,M)
Mean
Diff
Rms
End

On Thu, Jan 12, 2017 at 4:11 PM Bob Stewart <b...@evoria.net> wrote:

> Hi Bob,
>
> OK, like Bugs Bunny, I'll venture out on the limb, cut the limb, and see
> whether I fall or the tree falls:
>
> Wouldn't it take 1801 samples to get 18 seconds at 100S tau?  Maybe I
> didn't state that properly, but I think you get my meaning.  Also, I've
> never actually taken the time to look at the formula or the code to see how
> the ADEV is calculated.  But doesn't it use a sliding boxcar type of
> calculation?  Or is that some other *DEV?  My point is that for 1801
> seconds, aren't there a lot more than 18 samples put in the 100S bin?  And
> I've probably stated that incorrectly, too.
>
>
>
> Bob
>
>
>
>
>
>   From: Bob Camp <kb...@n1k.org>
>
>  To: Bob Stewart <b...@evoria.net>; Discussion of precise time and
> frequency measurement <time-nuts@febo.com>
>
>  Sent: Thursday, January 12, 2017 2:38 PM
>
>  Subject: Re: [time-nuts] General questions about making measurements with
> time interval counter.
>
>
>
> Hi
>
>
>
> Keep in mind that when you do 1800 samples at 1 second, that data will
> only meet the
>
> 100 sample requirement out to tau = 18 seconds. Past that you are in the
> “under 100 samples
>
> region”.
>
>
>
> Bob
>
>
>
> > On Jan 12, 2017, at 2:32 PM, Bob Stewart <b...@evoria.net> wrote:
>
> >
>
> > Hi Bob,
>
> > OK, thanks for explaining.  When you and others use highly technical
> terms like "small number of samples" it's not always clear to me what you
> mean.  =)  Ten samples?  That's not enough for anything.  Normally I run at
> least 1800 samples; at least if I plan to share them with someone.
>
> >
>
> > Bob -
>
> > AE6RV.com
>
> >
>
> > GFS GPSDO list:
>
> > groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>
> >
>
> >  From: Bob Camp <kb...@n1k.org>
>
> > To: Bob Stewart <b...@evoria.net>; Discussion of precise time and
> frequency measurement <time-nuts@febo.com>
>
> > Sent: Thursday, January 12, 2017 1:03 PM
>
> > Subject: Re: [time-nuts] General questions about making measurements
> with time interval counter.
>
> >
>
> > Hi
>
> >
>
> > It varies from 5370 to 5370. You see a lot of plots that run out to 10
> samples or less. Anything below 100 samples
>
> > is risky in some senses.
>
> >
>
> > Bob
>
> >
>
> >> On Jan 12, 2017, at 12:25 PM, Bob Stewart <b...@evoria.net> wrote:
>
> >>
>
> >> Hi Bob,
>
> >> OK, what's a small number of data points?  Attached is a screencap of
> captures for 25, 50, 75, 100, and 150 seconds.  Yeah, at 25 seconds, the 1S
> tau is up at 4.56E-11, but it falls pretty quickly.  I will mention that
> this particular 5370 is much better than my other one.  So, maybe this one
> is an exceptional example?
>
> >>
>
> >> Just for grins, I also included a screencap of the phase points.
>
> >>
>
> >> Bob -
>
> >> AE6RV.com
>
> >>
>
> >> GFS GPSDO list:
>
> >> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>
> >>
>
> >>  From: Bob Camp <kb...@n1k.org>
>
> >> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and
> frequency measurement <time-nuts@febo.com>
>
> >> Sent: Thursday, January 12, 2017 11:04 AM
>
> >> Subject: Re: [time-nuts] General questions about making measurements
> with time interval counter.
>
> >>
>
> >> Hi
>
> >>
>
> >> There is a big difference between RMS and single shot. Single shot, the
> 5370 is a very different beast.
>
> >> That’s not a big deal when you have a few thousand readings and it all
> averages down. Unfortunately
>
> >> we all love to do runs with a very small number of points and then draw
> conclusions from them. As the
>
> >> sample size goes down, you no longer have a 2 to 4 x 10^-11 beast, it’s
> more like 5X that.
>
> >>
>
> >> Bob
>
> >>
>
> >>
>
> >>> On Jan 12, 2017, at 11:31 AM, Bob Stewart <b...@evoria.net> wrote:
>
> >>>
>
> >>> Hi Bob,
>
> >>> No

Re: [time-nuts] General questions about making measurements with time interval counter.

[Bob Stewart]

Hi Bob,
OK, like Bugs Bunny, I'll venture out on the limb, cut the limb, and see 
whether I fall or the tree falls:
Wouldn't it take 1801 samples to get 18 seconds at 100S tau?  Maybe I didn't 
state that properly, but I think you get my meaning.  Also, I've never actually 
taken the time to look at the formula or the code to see how the ADEV is 
calculated.  But doesn't it use a sliding boxcar type of calculation?  Or is 
that some other *DEV?  My point is that for 1801 seconds, aren't there a lot 
more than 18 samples put in the 100S bin?  And I've probably stated that 
incorrectly, too.  

Bob


  From: Bob Camp <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
 Sent: Thursday, January 12, 2017 2:38 PM
 Subject: Re: [time-nuts] General questions about making measurements with time 
interval counter.
   
Hi

Keep in mind that when you do 1800 samples at 1 second, that data will only 
meet the 
100 sample requirement out to tau = 18 seconds. Past that you are in the “under 
100 samples
region”.

Bob

> On Jan 12, 2017, at 2:32 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> Hi Bob,
> OK, thanks for explaining.  When you and others use highly technical terms 
> like "small number of samples" it's not always clear to me what you mean.  =) 
>  Ten samples?  That's not enough for anything.  Normally I run at least 1800 
> samples; at least if I plan to share them with someone.
> 
> Bob -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
>      From: Bob Camp <kb...@n1k.org>
> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
> measurement <time-nuts@febo.com> 
> Sent: Thursday, January 12, 2017 1:03 PM
> Subject: Re: [time-nuts] General questions about making measurements with 
> time interval counter.
> 
> Hi
> 
> It varies from 5370 to 5370. You see a lot of plots that run out to 10 
> samples or less. Anything below 100 samples
> is risky in some senses.
> 
> Bob
> 
>> On Jan 12, 2017, at 12:25 PM, Bob Stewart <b...@evoria.net> wrote:
>> 
>> Hi Bob,
>> OK, what's a small number of data points?  Attached is a screencap of 
>> captures for 25, 50, 75, 100, and 150 seconds.  Yeah, at 25 seconds, the 1S 
>> tau is up at 4.56E-11, but it falls pretty quickly.  I will mention that 
>> this particular 5370 is much better than my other one.  So, maybe this one 
>> is an exceptional example?
>> 
>> Just for grins, I also included a screencap of the phase points.
>> 
>> Bob -
>> AE6RV.com
>> 
>> GFS GPSDO list:
>> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>> 
>>      From: Bob Camp <kb...@n1k.org>
>> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
>> measurement <time-nuts@febo.com> 
>> Sent: Thursday, January 12, 2017 11:04 AM
>> Subject: Re: [time-nuts] General questions about making measurements with 
>> time interval counter.
>> 
>> Hi
>> 
>> There is a big difference between RMS and single shot. Single shot, the 5370 
>> is a very different beast. 
>> That’s not a big deal when you have a few thousand readings and it all 
>> averages down. Unfortunately 
>> we all love to do runs with a very small number of points and then draw 
>> conclusions from them. As the 
>> sample size goes down, you no longer have a 2 to 4 x 10^-11 beast, it’s more 
>> like 5X that.
>> 
>> Bob
>> 
>> 
>>> On Jan 12, 2017, at 11:31 AM, Bob Stewart <b...@evoria.net> wrote:
>>> 
>>> Hi Bob,
>>> Normally I see somewhere between 2E-11 and 4E-11 at 1S tau on my 5370A, as 
>>> in the blue trace on the attached plot.  Am I misunderstanding your 
>>> meaning?  Granted, I am clocking the 5370A with a GPSDO, but I believe I 
>>> see about the same thing with the HP10811.  This test was 1PPS vs 1PPS on 
>>> two different units.
>>> The plot also has a test run by Tom, in orange, using his H Maser and a 
>>> Timepod to show how poor the 5370 is compared to the Timepod below about 
>>> 60S tau.  These are essentially apples vs apples tests.
>>> 
>>> Bob
>>> 
>>> 
>>> 
>>> 
>>>      From: Bob Camp <kb...@n1k.org>
>>> To: Discussion of precise time and frequency measurement 
>>> <time-nuts@febo.com> 
>>> Sent: Thursday, January 12, 2017 8:27 AM
>>> Subject: 

Re: [time-nuts] General questions about making measurements with time interval counter.

[Bob Camp]

Hi

Keep in mind that when you do 1800 samples at 1 second, that data will only 
meet the 
100 sample requirement out to tau = 18 seconds. Past that you are in the “under 
100 samples
region”.

Bob

> On Jan 12, 2017, at 2:32 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> Hi Bob,
> OK, thanks for explaining.  When you and others use highly technical terms 
> like "small number of samples" it's not always clear to me what you mean.  =) 
>  Ten samples?  That's not enough for anything.  Normally I run at least 1800 
> samples; at least if I plan to share them with someone.
> 
> Bob -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
>  From: Bob Camp <kb...@n1k.org>
> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
> measurement <time-nuts@febo.com> 
> Sent: Thursday, January 12, 2017 1:03 PM
> Subject: Re: [time-nuts] General questions about making measurements with 
> time interval counter.
> 
> Hi
> 
> It varies from 5370 to 5370. You see a lot of plots that run out to 10 
> samples or less. Anything below 100 samples
> is risky in some senses.
> 
> Bob
> 
>> On Jan 12, 2017, at 12:25 PM, Bob Stewart <b...@evoria.net> wrote:
>> 
>> Hi Bob,
>> OK, what's a small number of data points?  Attached is a screencap of 
>> captures for 25, 50, 75, 100, and 150 seconds.  Yeah, at 25 seconds, the 1S 
>> tau is up at 4.56E-11, but it falls pretty quickly.  I will mention that 
>> this particular 5370 is much better than my other one.  So, maybe this one 
>> is an exceptional example?
>> 
>> Just for grins, I also included a screencap of the phase points.
>> 
>> Bob -
>> AE6RV.com
>> 
>> GFS GPSDO list:
>> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
>> 
>>   From: Bob Camp <kb...@n1k.org>
>> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
>> measurement <time-nuts@febo.com> 
>> Sent: Thursday, January 12, 2017 11:04 AM
>> Subject: Re: [time-nuts] General questions about making measurements with 
>> time interval counter.
>> 
>> Hi
>> 
>> There is a big difference between RMS and single shot. Single shot, the 5370 
>> is a very different beast. 
>> That’s not a big deal when you have a few thousand readings and it all 
>> averages down. Unfortunately 
>> we all love to do runs with a very small number of points and then draw 
>> conclusions from them. As the 
>> sample size goes down, you no longer have a 2 to 4 x 10^-11 beast, it’s more 
>> like 5X that.
>> 
>> Bob
>> 
>> 
>>> On Jan 12, 2017, at 11:31 AM, Bob Stewart <b...@evoria.net> wrote:
>>> 
>>> Hi Bob,
>>> Normally I see somewhere between 2E-11 and 4E-11 at 1S tau on my 5370A, as 
>>> in the blue trace on the attached plot.  Am I misunderstanding your 
>>> meaning?  Granted, I am clocking the 5370A with a GPSDO, but I believe I 
>>> see about the same thing with the HP10811.  This test was 1PPS vs 1PPS on 
>>> two different units.
>>> The plot also has a test run by Tom, in orange, using his H Maser and a 
>>> Timepod to show how poor the 5370 is compared to the Timepod below about 
>>> 60S tau.  These are essentially apples vs apples tests.
>>> 
>>> Bob
>>> 
>>> 
>>> 
>>> 
>>>   From: Bob Camp <kb...@n1k.org>
>>> To: Discussion of precise time and frequency measurement 
>>> <time-nuts@febo.com> 
>>> Sent: Thursday, January 12, 2017 8:27 AM
>>> Subject: Re: [time-nuts] General questions about making measurements with 
>>> time interval counter.
>>> 
>>> Hi
>>> 
>>> There are a number of ways to improve the resolution (and accuracy) of your 
>>> data without spending 
>>> big piles of cash. They have been discussed here on the list many times 
>>> over the last few years. 
>>> What I’m suggesting is that you dig into that ahead of taking data. You 
>>> will dive into it eventually as you 
>>> look more and more at devices that are locked to some sort of stable 
>>> reference internally. 
>>> 
>>> Ideally you would like a device with a floor 5X to 10X better than what you 
>>> are measuring. For ADEV style
>>> data, the 5370 is a 1x10^-10 sort of device single shot (so 1x10^-9 is the 
>>> limit at 10

Re: [time-nuts] General questions about making measurements with time interval counter.

[Bob Stewart]

Hi Bob,
OK, thanks for explaining.  When you and others use highly technical terms like 
"small number of samples" it's not always clear to me what you mean.  =)  Ten 
samples?  That's not enough for anything.  Normally I run at least 1800 
samples; at least if I plan to share them with someone.

Bob -
AE6RV.com

GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info

  From: Bob Camp <kb...@n1k.org>
 To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
measurement <time-nuts@febo.com> 
 Sent: Thursday, January 12, 2017 1:03 PM
 Subject: Re: [time-nuts] General questions about making measurements with time 
interval counter.
   
Hi

It varies from 5370 to 5370. You see a lot of plots that run out to 10 samples 
or less. Anything below 100 samples
is risky in some senses.

Bob

> On Jan 12, 2017, at 12:25 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> Hi Bob,
> OK, what's a small number of data points?  Attached is a screencap of 
> captures for 25, 50, 75, 100, and 150 seconds.  Yeah, at 25 seconds, the 1S 
> tau is up at 4.56E-11, but it falls pretty quickly.  I will mention that this 
> particular 5370 is much better than my other one.  So, maybe this one is an 
> exceptional example?
> 
> Just for grins, I also included a screencap of the phase points.
> 
> Bob -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
>      From: Bob Camp <kb...@n1k.org>
> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
> measurement <time-nuts@febo.com> 
> Sent: Thursday, January 12, 2017 11:04 AM
> Subject: Re: [time-nuts] General questions about making measurements with 
> time interval counter.
> 
> Hi
> 
> There is a big difference between RMS and single shot. Single shot, the 5370 
> is a very different beast. 
> That’s not a big deal when you have a few thousand readings and it all 
> averages down. Unfortunately 
> we all love to do runs with a very small number of points and then draw 
> conclusions from them. As the 
> sample size goes down, you no longer have a 2 to 4 x 10^-11 beast, it’s more 
> like 5X that.
> 
> Bob
> 
> 
>> On Jan 12, 2017, at 11:31 AM, Bob Stewart <b...@evoria.net> wrote:
>> 
>> Hi Bob,
>> Normally I see somewhere between 2E-11 and 4E-11 at 1S tau on my 5370A, as 
>> in the blue trace on the attached plot.  Am I misunderstanding your meaning? 
>>  Granted, I am clocking the 5370A with a GPSDO, but I believe I see about 
>> the same thing with the HP10811.  This test was 1PPS vs 1PPS on two 
>> different units.
>> The plot also has a test run by Tom, in orange, using his H Maser and a 
>> Timepod to show how poor the 5370 is compared to the Timepod below about 60S 
>> tau.  These are essentially apples vs apples tests.
>> 
>> Bob
>> 
>> 
>> 
>> 
>>      From: Bob Camp <kb...@n1k.org>
>> To: Discussion of precise time and frequency measurement 
>> <time-nuts@febo.com> 
>> Sent: Thursday, January 12, 2017 8:27 AM
>> Subject: Re: [time-nuts] General questions about making measurements with 
>> time interval counter.
>> 
>> Hi
>> 
>> There are a number of ways to improve the resolution (and accuracy) of your 
>> data without spending 
>> big piles of cash. They have been discussed here on the list many times over 
>> the last few years. 
>> What I’m suggesting is that you dig into that ahead of taking data. You will 
>> dive into it eventually as you 
>> look more and more at devices that are locked to some sort of stable 
>> reference internally. 
>> 
>> Ideally you would like a device with a floor 5X to 10X better than what you 
>> are measuring. For ADEV style
>> data, the 5370 is a 1x10^-10 sort of device single shot (so 1x10^-9 is the 
>> limit at 10:1). With a lot of averaging 
>> (which is not something you do with ADEV) you can get about 5X better than 
>> that as a floor. In either case, it is getting in the way of any
>> readings that are much below 1x10^-9 at one second. A low cost XO can hit 
>> that level of performance.  
>> 
>> Bob
>> 
>> 
>> ___
>> 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.
> 
> 
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Re: [time-nuts] General questions about making measurements with time interval counter.

[Bob Camp]

Hi

It varies from 5370 to 5370. You see a lot of plots that run out to 10 samples 
or less. Anything below 100 samples
is risky in some senses.

Bob

> On Jan 12, 2017, at 12:25 PM, Bob Stewart <b...@evoria.net> wrote:
> 
> Hi Bob,
> OK, what's a small number of data points?  Attached is a screencap of 
> captures for 25, 50, 75, 100, and 150 seconds.  Yeah, at 25 seconds, the 1S 
> tau is up at 4.56E-11, but it falls pretty quickly.  I will mention that this 
> particular 5370 is much better than my other one.  So, maybe this one is an 
> exceptional example?
> 
> Just for grins, I also included a screencap of the phase points.
> 
> Bob -
> AE6RV.com
> 
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> 
>  From: Bob Camp <kb...@n1k.org>
> To: Bob Stewart <b...@evoria.net>; Discussion of precise time and frequency 
> measurement <time-nuts@febo.com> 
> Sent: Thursday, January 12, 2017 11:04 AM
> Subject: Re: [time-nuts] General questions about making measurements with 
> time interval counter.
> 
> Hi
> 
> There is a big difference between RMS and single shot. Single shot, the 5370 
> is a very different beast. 
> That’s not a big deal when you have a few thousand readings and it all 
> averages down. Unfortunately 
> we all love to do runs with a very small number of points and then draw 
> conclusions from them. As the 
> sample size goes down, you no longer have a 2 to 4 x 10^-11 beast, it’s more 
> like 5X that.
> 
> Bob
> 
> 
>> On Jan 12, 2017, at 11:31 AM, Bob Stewart <b...@evoria.net> wrote:
>> 
>> Hi Bob,
>> Normally I see somewhere between 2E-11 and 4E-11 at 1S tau on my 5370A, as 
>> in the blue trace on the attached plot.  Am I misunderstanding your meaning? 
>>  Granted, I am clocking the 5370A with a GPSDO, but I believe I see about 
>> the same thing with the HP10811.  This test was 1PPS vs 1PPS on two 
>> different units.
>> The plot also has a test run by Tom, in orange, using his H Maser and a 
>> Timepod to show how poor the 5370 is compared to the Timepod below about 60S 
>> tau.  These are essentially apples vs apples tests.
>> 
>> Bob
>> 
>> 
>> 
>> 
>>   From: Bob Camp <kb...@n1k.org>
>> To: Discussion of precise time and frequency measurement 
>> <time-nuts@febo.com> 
>> Sent: Thursday, January 12, 2017 8:27 AM
>> Subject: Re: [time-nuts] General questions about making measurements with 
>> time interval counter.
>> 
>> Hi
>> 
>> There are a number of ways to improve the resolution (and accuracy) of your 
>> data without spending 
>> big piles of cash. They have been discussed here on the list many times over 
>> the last few years. 
>> What I’m suggesting is that you dig into that ahead of taking data. You will 
>> dive into it eventually as you 
>> look more and more at devices that are locked to some sort of stable 
>> reference internally. 
>> 
>> Ideally you would like a device with a floor 5X to 10X better than what you 
>> are measuring. For ADEV style
>> data, the 5370 is a 1x10^-10 sort of device single shot (so 1x10^-9 is the 
>> limit at 10:1). With a lot of averaging 
>> (which is not something you do with ADEV) you can get about 5X better than 
>> that as a floor. In either case, it is getting in the way of any
>> readings that are much below 1x10^-9 at one second. A low cost XO can hit 
>> that level of performance.  
>> 
>> Bob
>> 
>> 
>> ___
>> 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.
> 
> 
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> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] General questions about making measurements with time interval counter.

[Bob Camp]

Hi

There is a big difference between RMS and single shot. Single shot, the 5370 is 
a very different beast. 
That’s not a big deal when you have a few thousand readings and it all averages 
down. Unfortunately 
we all love to do runs with a very small number of points and then draw 
conclusions from them. As the 
sample size goes down, you no longer have a 2 to 4 x 10^-11 beast, it’s more 
like 5X that.

Bob


> On Jan 12, 2017, at 11:31 AM, Bob Stewart <b...@evoria.net> wrote:
> 
> Hi Bob,
> Normally I see somewhere between 2E-11 and 4E-11 at 1S tau on my 5370A, as in 
> the blue trace on the attached plot.  Am I misunderstanding your meaning?  
> Granted, I am clocking the 5370A with a GPSDO, but I believe I see about the 
> same thing with the HP10811.  This test was 1PPS vs 1PPS on two different 
> units.
> The plot also has a test run by Tom, in orange, using his H Maser and a 
> Timepod to show how poor the 5370 is compared to the Timepod below about 60S 
> tau.  These are essentially apples vs apples tests.
> 
> Bob
> 
> 
> 
> 
>  From: Bob Camp <kb...@n1k.org>
> To: Discussion of precise time and frequency measurement <time-nuts@febo.com> 
> Sent: Thursday, January 12, 2017 8:27 AM
> Subject: Re: [time-nuts] General questions about making measurements with 
> time interval counter.
> 
> Hi
> 
> There are a number of ways to improve the resolution (and accuracy) of your 
> data without spending 
> big piles of cash. They have been discussed here on the list many times over 
> the last few years. 
> What I’m suggesting is that you dig into that ahead of taking data. You will 
> dive into it eventually as you 
> look more and more at devices that are locked to some sort of stable 
> reference internally. 
> 
> Ideally you would like a device with a floor 5X to 10X better than what you 
> are measuring. For ADEV style
> data, the 5370 is a 1x10^-10 sort of device single shot (so 1x10^-9 is the 
> limit at 10:1). With a lot of averaging 
> (which is not something you do with ADEV) you can get about 5X better than 
> that as a floor. In either case, it is getting in the way of any
> readings that are much below 1x10^-9 at one second. A low cost XO can hit 
> that level of performance.  
> 
> Bob
> 
> 
> ___
> 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.

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Re: [time-nuts] General questions about making measurements with time interval counter.

[Bob Stewart]

Hi Bob,
Normally I see somewhere between 2E-11 and 4E-11 at 1S tau on my 5370A, as in 
the blue trace on the attached plot.  Am I misunderstanding your meaning?  
Granted, I am clocking the 5370A with a GPSDO, but I believe I see about the 
same thing with the HP10811.  This test was 1PPS vs 1PPS on two different units.
The plot also has a test run by Tom, in orange, using his H Maser and a Timepod 
to show how poor the 5370 is compared to the Timepod below about 60S tau.  
These are essentially apples vs apples tests.

Bob




  From: Bob Camp <kb...@n1k.org>
 To: Discussion of precise time and frequency measurement <time-nuts@febo.com> 
 Sent: Thursday, January 12, 2017 8:27 AM
 Subject: Re: [time-nuts] General questions about making measurements with time 
interval counter.
   
Hi

There are a number of ways to improve the resolution (and accuracy) of your 
data without spending 
big piles of cash. They have been discussed here on the list many times over 
the last few years. 
What I’m suggesting is that you dig into that ahead of taking data. You will 
dive into it eventually as you 
look more and more at devices that are locked to some sort of stable reference 
internally. 

Ideally you would like a device with a floor 5X to 10X better than what you are 
measuring. For ADEV style
data, the 5370 is a 1x10^-10 sort of device single shot (so 1x10^-9 is the 
limit at 10:1). With a lot of averaging 
(which is not something you do with ADEV) you can get about 5X better than that 
as a floor. In either case, it is getting in the way of any
readings that are much below 1x10^-9 at one second. A low cost XO can hit that 
level of performance.  

Bob


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Re: [time-nuts] General questions about making measurements with time interval counter.

[Bob Camp]

Hi

There are a number of ways to improve the resolution (and accuracy) of your 
data without spending 
big piles of cash. They have been discussed here on the list many times over 
the last few years. 
What I’m suggesting is that you dig into that ahead of taking data. You will 
dive into it eventually as you 
look more and more at devices that are locked to some sort of stable reference 
internally. 

Ideally you would like a device with a floor 5X to 10X better than what you are 
measuring. For ADEV style
data, the 5370 is a 1x10^-10 sort of device single shot (so 1x10^-9 is the 
limit at 10:1). With a lot of averaging 
(which is not something you do with ADEV) you can get about 5X better than that 
as a floor. In either case, it is getting in the way of any
readings that are much below 1x10^-9 at one second. A low cost XO can hit that 
level of performance.  

Bob

> On Jan 12, 2017, at 4:36 AM, Dr. David Kirkby (Kirkby Microwave Ltd) 
>  wrote:
> 
> On 12 January 2017 at 02:31, Bob Camp  wrote:
> 
>> Hi
>> 
> 
> Hi Bob
> 
> 
>> 
>> The most basic issue you are going to run into is that your counter is not
>> high enough
>> resolution / accuracy to give you meaningful data for time intervals under
>> a few hundred
>> seconds.
> 
> 
> Is that true if I'm not testing very high quality sources? There are
> significant differences observed between these two setups
> 
> 1) START and STOP from distribution amplifier.
> 2) START from distribution amplifier. STOP from Stanford Research SR345 30
> MHz function generator set to produce 10 MHz.
> 
> 1) ADEV plot at http://www.kirkbymicrowave.co.uk/time-stuff/ADEV.PNG
> where ADEV is about 5x poorer on the function generator at 100 seconds
> 
> 2) MDEV plot at http://www.kirkbymicrowave.co.uk/time-stuff/MDEV.PNG
> where MDEV is about 5 x poorer on the function generator at 10 seconds.
> 
> The raw data is in the same directory
> http://www.kirkbymicrowave.co.uk/time-stuff/ . I should have zipped that,
> as it is quite large
> 
> I'm pretty sure the HP 83623A 20 GHz sweep generator will be a lot worst
> than either of those, as a simple check of the standard deviation on the
> display of the HP 5370B (no data collected from GPIB), showed much higher
> SD on the microwave sweeper than the function generator.
> 
> I can see if I were testing masers, Cs source, and decent GPS receivers,
> what you say would be true. But is it true for lesser quality sources?
> Maybe testing lesser quality sources is not such a stupid idea, as the
> instrumentation is less of a limiting factor.
> 
> I admit I did say in my original post SHORT/MEDIUM time scales, and I guess
> 10/100s is not short.
> 
> 
> 
>> I would focus on improving on that part of things before I went off on a
>> major
>> “test everything” adventure.
> 
> 
> But is there any way without spending lots of cash? The following
> instruments are out of the question due to price
> 
> * Keysight 53230A 350 MHz Universal Frequency Counter/Timer, 12 digits/s,
> 20 ps
> * John's Timepod
> 
> A Stanford Research SR620 is not out of the question. I did have one
> before, but swapped it, along with a 4.2 GHz signal generator for an
> HP4391B impedance/material analyzer. The 5370B came along fairly cheap
> ($300), but I don't mind spending more on  a SR620. But will that gain me
> much? I know the single shot resolution is a bit better than the 5370B, but
> it does not appear to be a massive improvement, given they are 3~4 x the
> cost.on the used market.
> 
> I also have many other contraiints, which limit what I can realistically
> achieve
> 
> * Small lab in my garmage- opening door on lab will change temperature.
> * Single glazed window
> * Air con that is a standard unit designed for offices - not metrology
> labs.
> 
> Simply collecting a lot of data that is resolution limited is
>> not a lot of fun …..
>> 
> 
> Agreed. But am I doing that at > 10 seconds? Is the counter my limit on
> those two sets of data? I will collect some from the HP 83623A 20 GHz sweep
> generator later today, but that generates a lot of heat, and I'd rather let
> that warm up for a couple of hours before doing anything with that.
> 
> 
>> 
>> Bob
>> 
> 
> You clearly have a lot of knowledge Bob. Can I learn anything useful with
> what I have, or am I wasting my time?
> 
> Dave
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Re: [time-nuts] General questions about making measurements with time interval counter.

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 12 January 2017 at 02:31, Bob Camp  wrote:

> Hi
>

Hi Bob


>
> The most basic issue you are going to run into is that your counter is not
> high enough
> resolution / accuracy to give you meaningful data for time intervals under
> a few hundred
> seconds.


Is that true if I'm not testing very high quality sources? There are
significant differences observed between these two setups

1) START and STOP from distribution amplifier.
2) START from distribution amplifier. STOP from Stanford Research SR345 30
MHz function generator set to produce 10 MHz.

1) ADEV plot at http://www.kirkbymicrowave.co.uk/time-stuff/ADEV.PNG
where ADEV is about 5x poorer on the function generator at 100 seconds

2) MDEV plot at http://www.kirkbymicrowave.co.uk/time-stuff/MDEV.PNG
where MDEV is about 5 x poorer on the function generator at 10 seconds.

The raw data is in the same directory
http://www.kirkbymicrowave.co.uk/time-stuff/ . I should have zipped that,
as it is quite large

I'm pretty sure the HP 83623A 20 GHz sweep generator will be a lot worst
than either of those, as a simple check of the standard deviation on the
display of the HP 5370B (no data collected from GPIB), showed much higher
SD on the microwave sweeper than the function generator.

I can see if I were testing masers, Cs source, and decent GPS receivers,
what you say would be true. But is it true for lesser quality sources?
Maybe testing lesser quality sources is not such a stupid idea, as the
instrumentation is less of a limiting factor.

I admit I did say in my original post SHORT/MEDIUM time scales, and I guess
10/100s is not short.



> I would focus on improving on that part of things before I went off on a
> major
> “test everything” adventure.


But is there any way without spending lots of cash? The following
instruments are out of the question due to price

* Keysight 53230A 350 MHz Universal Frequency Counter/Timer, 12 digits/s,
20 ps
* John's Timepod

A Stanford Research SR620 is not out of the question. I did have one
before, but swapped it, along with a 4.2 GHz signal generator for an
HP4391B impedance/material analyzer. The 5370B came along fairly cheap
($300), but I don't mind spending more on  a SR620. But will that gain me
much? I know the single shot resolution is a bit better than the 5370B, but
it does not appear to be a massive improvement, given they are 3~4 x the
cost.on the used market.

I also have many other contraiints, which limit what I can realistically
achieve

* Small lab in my garmage- opening door on lab will change temperature.
* Single glazed window
* Air con that is a standard unit designed for offices - not metrology
labs.

Simply collecting a lot of data that is resolution limited is
> not a lot of fun …..
>

Agreed. But am I doing that at > 10 seconds? Is the counter my limit on
those two sets of data? I will collect some from the HP 83623A 20 GHz sweep
generator later today, but that generates a lot of heat, and I'd rather let
that warm up for a couple of hours before doing anything with that.


>
> Bob
>

You clearly have a lot of knowledge Bob. Can I learn anything useful with
what I have, or am I wasting my time?

Dave
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Re: [time-nuts] General questions about making measurements with time interval counter.

[Bob Camp]

Hi

The most basic issue you are going to run into is that your counter is not high 
enough
resolution / accuracy to give you meaningful data for time intervals under a 
few hundred
seconds. I would focus on improving on that part of things before I went off on 
a major
“test everything” adventure. Simply collecting a lot of data that is resolution 
limited is 
not a lot of fun …..

Bob

> On Jan 11, 2017, at 9:20 PM, Dr. David Kirkby (Kirkby Microwave Ltd) 
>  wrote:
> 
> MY AIMS
> 
> 1) Try to learn about the various statistical tests (ADEV, MDEV etc), and
> how best to compare oscillators, by making some measurements on various
> oscillators I have.
> 
> 2) Investigate the short/medium term stability of the output of  various
> bits of test kit. All are locked to GPS by feeding 10 MHz to their timebase
> inputs, so long term drift should not be relevant.
> 
> These istrumuments are:
> 
> a) The GPS itself - primarily a test of the 5370B time interval counter,
> distribution amplifier and general temperature fluctuations in the lab.
> 
> b) Other GPS(s) when I get 1 or 2 more.
> 
> c) 10 MHz to 20 GHz Microwave signal generator.
> 
> d) 0.001 Hz to 30 MHz function generator.
> 
> e) A VNA that will work at 10 MHz. Turn sweeping off
> 
> f) A VNA that has a minimum frequency of 50 MHz. Again turn sweeping off.
> 
> METHOD - Suggestion for improvements welcome.
> 
> * Where possible set all instruments to 10 MHz, which is the same as the
> GPS reference. (Obviously since one of the VNAs will not go below 50 MHz, I
> would need to use a higher frequency)
> * Feed GPS to the start input of the 5370B TI counter and the DUT into the
> stop input
> * Use the 5370B time interval counter to measre the time difference between
> one output of the distribution amplifier and the output of the instrument
> being tested .
> * Collect data from 5370B and use John's Timelab to plot various graphs and
> try to understand the differences between the various statical measurements
> (ADEV, MDEV etc.)
> 
> MY QUESTIONS.
> 
> 1) Should I use the GPS to provide a reference for the 5370B time interval
> counter,  or would it be better to use the internal OCXO? Currently I have
> the 5370B locked to GPS too, but I am wondering if this is a bad idea and I
> should run it from its own oscillator.
> 
> 2) Is there any advantage in a 10 MHz DUT going into the start or stop
> input? I assume that it is irrelevant, as long as the GPS goes into the
> other. But maybe not.
> 
> 3) If the DUT is higher in frequency (eg 50 MHz) than the 10  MHz GPS,  is
> there any advantage in going in the start ot stop input?
> 
> 4) If the DUT is lower in frequency (eg 5 MHz) than the 10  MHz GPS,  is
> there any advantage in going in the start ot stop input?
> 
> Dave
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