General questions about making measurements with time interval counter.
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 <kb8tq@n1k.org>
To: Bob Stewart bob@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 bob@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 kb8tq@n1k.org
To: Bob Stewart bob@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 bob@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 kb8tq@n1k.org
To: Bob Stewart bob@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 bob@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 kb8tq@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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and follow the instructions there.
<ADEVs.png><Phase.png>_______________________________________________
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and follow the instructions there.
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 bob@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 <kb8tq@n1k.org>
To: Bob Stewart bob@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 bob@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 <kb8tq@n1k.org>
To: Bob Stewart bob@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 bob@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 <kb8tq@n1k.org>
To: Bob Stewart bob@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 bob@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 <kb8tq@n1k.org>
To: Discussion of precise time and frequency measurement <
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
<ADEV.png>_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
and follow the instructions there.
<ADEVs.png><Phase.png>_______________________________________________
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and follow the instructions there.
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To unsubscribe, go to
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To unsubscribe, go to
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and follow the instructions there.
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.stobbe@gmail.com
To: "Bob Stewart" bob@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 bob@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 <kb8tq@n1k.org>
To: Bob Stewart bob@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 bob@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 <kb8tq@n1k.org>
To: Bob Stewart bob@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 bob@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 <kb8tq@n1k.org>
To: Bob Stewart bob@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 bob@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 <kb8tq@n1k.org>
To: Discussion of precise time and frequency measurement <
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
<ADEV.png>_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
and follow the instructions there.
<ADEVs.png><Phase.png>_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
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and follow the instructions there.
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To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
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 <tvb@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 + 2tau) < count; i += stride, n += 1)
sum += pow(phase[i + 2tau] - 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.stobbe@gmail.com
To: "Bob Stewart" bob@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 bob@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 kb8tq@n1k.org
To: Bob Stewart bob@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 bob@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 kb8tq@n1k.org
To: Bob Stewart bob@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 bob@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 kb8tq@n1k.org
To: Bob Stewart bob@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 bob@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 kb8tq@n1k.org
To: Discussion of precise time and frequency measurement <
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
<ADEV.png>_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
and follow the instructions there.
<ADEVs.png><Phase.png>_______________________________________________
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to
https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
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To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Hi
On Jan 12, 2017, at 4:06 PM, Bob Stewart bob@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 <kb8tq@n1k.org>
To: Bob Stewart bob@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 bob@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 <kb8tq@n1k.org>
To: Bob Stewart bob@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 bob@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 <kb8tq@n1k.org>
To: Bob Stewart bob@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 bob@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 <kb8tq@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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