BS
Bob Stewart
Thu, Jun 30, 2016 6:30 PM
With my recent Cs problems, I've been wondering about the subject of noise generation and measurement. Specifically, my question is this: Let's say that I have 3 disciplined oscillators: A, B, and C. So, I use the same 5370 to create a 1000 second ADEV and discover that the 1s noise value between A and B is low, while the 1s noise between A and C, as well as B and C is high. Can I then say that both A and B are low noise devices? Or is it possible that even though I'm measuring 1000 points, both A and B are high noise devices, but somehow are noisy in the same exact way, and it's actually C that's the low noise oscillator?
Bob - AE6RV -----------------------------------------------------------------------------------
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
With my recent Cs problems, I've been wondering about the subject of noise generation and measurement. Specifically, my question is this: Let's say that I have 3 disciplined oscillators: A, B, and C. So, I use the same 5370 to create a 1000 second ADEV and discover that the 1s noise value between A and B is low, while the 1s noise between A and C, as well as B and C is high. Can I then say that both A and B are low noise devices? Or is it possible that even though I'm measuring 1000 points, both A and B are high noise devices, but somehow are noisy in the same exact way, and it's actually C that's the low noise oscillator?
Bob - AE6RV -----------------------------------------------------------------------------------
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
PS
paul swed
Thu, Jun 30, 2016 7:35 PM
Bob,
I am about to get myself into a lot of trouble. If the noise is coherent in
some way then its not really noise anymore its a signal or its filtered in
some way as compared to C.
There you go I feel the hot emails on the way already.
Should be a good read.
Regards
Paul
WB8TSL
On Thu, Jun 30, 2016 at 2:30 PM, Bob Stewart bob@evoria.net wrote:
With my recent Cs problems, I've been wondering about the subject of noise
generation and measurement. Specifically, my question is this: Let's say
that I have 3 disciplined oscillators: A, B, and C. So, I use the same
5370 to create a 1000 second ADEV and discover that the 1s noise value
between A and B is low, while the 1s noise between A and C, as well as B
and C is high. Can I then say that both A and B are low noise devices? Or
is it possible that even though I'm measuring 1000 points, both A and B are
high noise devices, but somehow are noisy in the same exact way, and it's
actually C that's the low noise oscillator?
Bob -
AE6RV -----------------------------------------------------------------------------------
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
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.
Bob,
I am about to get myself into a lot of trouble. If the noise is coherent in
some way then its not really noise anymore its a signal or its filtered in
some way as compared to C.
There you go I feel the hot emails on the way already.
Should be a good read.
Regards
Paul
WB8TSL
On Thu, Jun 30, 2016 at 2:30 PM, Bob Stewart <bob@evoria.net> wrote:
> With my recent Cs problems, I've been wondering about the subject of noise
> generation and measurement. Specifically, my question is this: Let's say
> that I have 3 disciplined oscillators: A, B, and C. So, I use the same
> 5370 to create a 1000 second ADEV and discover that the 1s noise value
> between A and B is low, while the 1s noise between A and C, as well as B
> and C is high. Can I then say that both A and B are low noise devices? Or
> is it possible that even though I'm measuring 1000 points, both A and B are
> high noise devices, but somehow are noisy in the same exact way, and it's
> actually C that's the low noise oscillator?
>
> Bob -
> AE6RV -----------------------------------------------------------------------------------
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> _______________________________________________
> 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.
>
AK
Attila Kinali
Thu, Jun 30, 2016 7:38 PM
On Thu, 30 Jun 2016 18:30:35 +0000 (UTC)
Bob Stewart bob@evoria.net wrote:
With my recent Cs problems, I've been wondering about the subject of noise
generation and measurement. Specifically, my question is this: Let's say
that I have 3 disciplined oscillators: A, B, and C. So, I use the same 5370
to create a 1000 second ADEV and discover that the 1s noise value between A
and B is low, while the 1s noise between A and C, as well as B and C is
high. Can I then say that both A and B are low noise devices? Or is it
possible that even though I'm measuring 1000 points, both A and B are high
noise devices, but somehow are noisy in the same exact way, and it's
actually C that's the low noise oscillator?
Short answer: yes
Long answer: Yes, but unlikely
:-)
You can see the output of the oscillators as random processes and model
them as such (MIT opencoursware has some good lectures on that topic).
If the processes are all independent, then you can assume that A and B
will have the lowest noise and estimate the ADEV values of C and the
second nosiest oscillator with good confidence, and of the lowest noise
oscillator with some confidence (keyword: "three cornered hat").
In reality you will never have totally independent oscillators, there
will be always some coupling through power supplies (even mains power)
or through RF coupling. Heck, even your measurement instrument might
couple the oscillators if you are not very carefull. So it really might
be that A and B are just bad oscillators, that injection locked to
each other, and thus seemed more stable/less noisy than A+C and B+C.
But generally, high stability/low noise oscillators are usually made
such, that the output and the power supply are decoupled from the
oscillator itself as much as possible, to make the effect of coupling
(which is always present) so small that it get swamped out by all
other noise sources.
Attila Kinali
--
Malek's Law:
Any simple idea will be worded in the most complicated way.
On Thu, 30 Jun 2016 18:30:35 +0000 (UTC)
Bob Stewart <bob@evoria.net> wrote:
> With my recent Cs problems, I've been wondering about the subject of noise
> generation and measurement. Specifically, my question is this: Let's say
> that I have 3 disciplined oscillators: A, B, and C. So, I use the same 5370
> to create a 1000 second ADEV and discover that the 1s noise value between A
> and B is low, while the 1s noise between A and C, as well as B and C is
> high. Can I then say that both A and B are low noise devices? Or is it
> possible that even though I'm measuring 1000 points, both A and B are high
> noise devices, but somehow are noisy in the same exact way, and it's
> actually C that's the low noise oscillator?
Short answer: yes
Long answer: Yes, but unlikely
:-)
You can see the output of the oscillators as random processes and model
them as such (MIT opencoursware has some good lectures on that topic).
If the processes are all independent, then you can assume that A and B
will have the lowest noise and estimate the ADEV values of C and the
second nosiest oscillator with good confidence, and of the lowest noise
oscillator with some confidence (keyword: "three cornered hat").
In reality you will never have totally independent oscillators, there
will be always some coupling through power supplies (even mains power)
or through RF coupling. Heck, even your measurement instrument might
couple the oscillators if you are not very carefull. So it really might
be that A and B are just bad oscillators, that injection locked to
each other, and thus seemed more stable/less noisy than A+C and B+C.
But generally, high stability/low noise oscillators are usually made
such, that the output and the power supply are decoupled from the
oscillator itself as much as possible, to make the effect of coupling
(which is always present) so small that it get swamped out by all
other noise sources.
Attila Kinali
--
Malek's Law:
Any simple idea will be worded in the most complicated way.
BC
Bob Camp
Thu, Jun 30, 2016 9:27 PM
Hi
If you are measuring noise, then C is the bad one in the group. If you are measuring something else, then it is
possible that you are getting bad information. This is a classic argument about comparing devices from the
same lot of parts. They might both have a very similar warmup curve or temperature or pressure coefficient.
Bob
On Jun 30, 2016, at 2:30 PM, Bob Stewart bob@evoria.net wrote:
With my recent Cs problems, I've been wondering about the subject of noise generation and measurement. Specifically, my question is this: Let's say that I have 3 disciplined oscillators: A, B, and C. So, I use the same 5370 to create a 1000 second ADEV and discover that the 1s noise value between A and B is low, while the 1s noise between A and C, as well as B and C is high. Can I then say that both A and B are low noise devices? Or is it possible that even though I'm measuring 1000 points, both A and B are high noise devices, but somehow are noisy in the same exact way, and it's actually C that's the low noise oscillator?
Bob - AE6RV -----------------------------------------------------------------------------------
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
time-nuts mailing list -- time-nuts@febo.com
To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.
Hi
If you are measuring noise, then C is the bad one in the group. If you are measuring something else, then it is
possible that you are getting bad information. This is a classic argument about comparing devices from the
same lot of parts. They might both have a very similar warmup curve or temperature or pressure coefficient.
Bob
> On Jun 30, 2016, at 2:30 PM, Bob Stewart <bob@evoria.net> wrote:
>
> With my recent Cs problems, I've been wondering about the subject of noise generation and measurement. Specifically, my question is this: Let's say that I have 3 disciplined oscillators: A, B, and C. So, I use the same 5370 to create a 1000 second ADEV and discover that the 1s noise value between A and B is low, while the 1s noise between A and C, as well as B and C is high. Can I then say that both A and B are low noise devices? Or is it possible that even though I'm measuring 1000 points, both A and B are high noise devices, but somehow are noisy in the same exact way, and it's actually C that's the low noise oscillator?
>
> Bob - AE6RV -----------------------------------------------------------------------------------
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> _______________________________________________
> 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.
BS
Bob Stewart
Fri, Jul 1, 2016 1:43 AM
Thanks Bob and Attila,
This problem with the Cs kind of brought the whole question of noise and what ADEVs mean into focus for me. Like most newbies, I had read about the ever increasing stability of time standards and wondered how they could actually know that they were better. I've seen the term 3-cornered hat bandied about, but I didn't really grock it until now.
Bob -----------------------------------------------------------------------------------
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, June 30, 2016 4:27 PM
Subject: Re: [time-nuts] The Nature of Noise
Hi
If you are measuring noise, then C is the bad one in the group. If you are measuring something else, then it is
possible that you are getting bad information. This is a classic argument about comparing devices from the
same lot of parts. They might both have a very similar warmup curve or temperature or pressure coefficient.
Bob
On Jun 30, 2016, at 2:30 PM, Bob Stewart bob@evoria.net wrote:
With my recent Cs problems, I've been wondering about the subject of noise generation and measurement. Specifically, my question is this: Let's say that I have 3 disciplined oscillators: A, B, and C. So, I use the same 5370 to create a 1000 second ADEV and discover that the 1s noise value between A and B is low, while the 1s noise between A and C, as well as B and C is high. Can I then say that both A and B are low noise devices? Or is it possible that even though I'm measuring 1000 points, both A and B are high noise devices, but somehow are noisy in the same exact way, and it's actually C that's the low noise oscillator?
Bob - AE6RV -----------------------------------------------------------------------------------
GFS GPSDO list:
groups.yahoo.com/neo/groups/GFS-GPSDOs/info
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.
Thanks Bob and Attila,
This problem with the Cs kind of brought the whole question of noise and what ADEVs mean into focus for me. Like most newbies, I had read about the ever increasing stability of time standards and wondered how they could actually know that they were better. I've seen the term 3-cornered hat bandied about, but I didn't really grock it until now.
Bob -----------------------------------------------------------------------------------
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, June 30, 2016 4:27 PM
Subject: Re: [time-nuts] The Nature of Noise
Hi
If you are measuring noise, then C is the bad one in the group. If you are measuring something else, then it is
possible that you are getting bad information. This is a classic argument about comparing devices from the
same lot of parts. They might both have a very similar warmup curve or temperature or pressure coefficient.
Bob
> On Jun 30, 2016, at 2:30 PM, Bob Stewart <bob@evoria.net> wrote:
>
> With my recent Cs problems, I've been wondering about the subject of noise generation and measurement. Specifically, my question is this: Let's say that I have 3 disciplined oscillators: A, B, and C. So, I use the same 5370 to create a 1000 second ADEV and discover that the 1s noise value between A and B is low, while the 1s noise between A and C, as well as B and C is high. Can I then say that both A and B are low noise devices? Or is it possible that even though I'm measuring 1000 points, both A and B are high noise devices, but somehow are noisy in the same exact way, and it's actually C that's the low noise oscillator?
>
> Bob - AE6RV -----------------------------------------------------------------------------------
> GFS GPSDO list:
> groups.yahoo.com/neo/groups/GFS-GPSDOs/info
> _______________________________________________
> 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.
