Empathy List Archives

DB

Dr Bruce Griffiths

Wed, Apr 11, 2007 11:44 PM

Tom Van Baak wrote:

6a

I used a 100k sample average which yields (IIRC) 200 femtosecond
resolution in the 5370B, and for each run checked the min, max, and
standard deviation statistics to make sure nothing goofy was going on
Standard deviation for a run like that on my 5370B is typically 30 to 40ps.

John

30-40 ps seems OK to me. But are you saying then that you
get a measured value to 200 fs resolution but with +/- 30 ps
standard deviation? This doesn't feel right at all. It seems to me
if your sdev is +/- 30 ps it is incorrect to even write down the
measured values to ps levels; and fs are out of the question.

/

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Tom

I assume the standard deviation is that of the population of 100K
measurements and not the standard deviation of their mean, which should
be around 95-126 fs.
Averaging of course does nothing to reduce systematic errors which can
be as high as 100ps in a 5370A/B. However for cable matching purposes
systematic errors largely cancel out.

Bruce

Tom Van Baak wrote: > 6a > > >> I used a 100k sample average which yields (IIRC) 200 femtosecond >> resolution in the 5370B, and for each run checked the min, max, and >> standard deviation statistics to make sure nothing goofy was going on >> Standard deviation for a run like that on my 5370B is typically 30 to 40ps. >> >> John >> > > 30-40 ps seems OK to me. But are you saying then that you > get a measured value to 200 fs resolution but with +/- 30 ps > standard deviation? This doesn't feel right at all. It seems to me > if your sdev is +/- 30 ps it is incorrect to even write down the > measured values to ps levels; and fs are out of the question. > > / > > > _______________________________________________ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > Tom I assume the standard deviation is that of the population of 100K measurements and not the standard deviation of their mean, which should be around 95-126 fs. Averaging of course does nothing to reduce systematic errors which can be as high as 100ps in a 5370A/B. However for cable matching purposes systematic errors largely cancel out. Bruce

JG

Joseph Gray

Wed, May 16, 2007 11:20 PM

I am running the Meinberg NTP software on two PCs. Both PCs are running
WinXP w/SP2, both are on the same network and both are syncing to servers at
pool.ntp.org. In the past, both clocks have shown that the two PCs had the
same time. Today, I just noticed that one of the PCs is running about 9
seconds fast, compared to my Casio WWVB watch.

As far as I know, nothing has changed to account for the difference. The PC
that is fast has been running without a reboot for three months. Does anyone
have any ideas?

I am running the Meinberg NTP software on two PCs. Both PCs are running WinXP w/SP2, both are on the same network and both are syncing to servers at pool.ntp.org. In the past, both clocks have shown that the two PCs had the same time. Today, I just noticed that one of the PCs is running about 9 seconds fast, compared to my Casio WWVB watch. As far as I know, nothing has changed to account for the difference. The PC that is fast has been running without a reboot for three months. Does anyone have any ideas?

DB

Dr Bruce Griffiths

Wed, May 16, 2007 11:48 PM

Joseph Gray wrote:

I am running the Meinberg NTP software on two PCs. Both PCs are running
WinXP w/SP2, both are on the same network and both are syncing to servers at
pool.ntp.org. In the past, both clocks have shown that the two PCs had the
same time. Today, I just noticed that one of the PCs is running about 9
seconds fast, compared to my Casio WWVB watch.

As far as I know, nothing has changed to account for the difference. The PC
that is fast has been running without a reboot for three months. Does anyone
have any ideas?

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Joseph

Are both machines syncing to the same ntp erver?
One or both of them of them hasn't synced to 127.127.1.0 by any chance?

Bruce

Joseph Gray wrote: > I am running the Meinberg NTP software on two PCs. Both PCs are running > WinXP w/SP2, both are on the same network and both are syncing to servers at > pool.ntp.org. In the past, both clocks have shown that the two PCs had the > same time. Today, I just noticed that one of the PCs is running about 9 > seconds fast, compared to my Casio WWVB watch. > > As far as I know, nothing has changed to account for the difference. The PC > that is fast has been running without a reboot for three months. Does anyone > have any ideas? > > > _______________________________________________ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > Joseph Are both machines syncing to the same ntp erver? One or both of them of them hasn't synced to 127.127.1.0 by any chance? Bruce

JG

Joseph Gray

Thu, May 17, 2007 12:01 AM

Are both machines syncing to the same ntp erver?
One or both of them of them hasn't synced to 127.127.1.0 by any chance?

Bruce

Although they are both using the pool at ntp.org, they are currently syncing
to different servers. They both are syncing to stratum 2 servers. Neither is
syncing to 127.127.1.0.

> Are both machines syncing to the same ntp erver? > One or both of them of them hasn't synced to 127.127.1.0 by any chance? > > Bruce Although they are both using the pool at ntp.org, they are currently syncing to different servers. They both are syncing to stratum 2 servers. Neither is syncing to 127.127.1.0.

DB

Dr Bruce Griffiths

Thu, May 17, 2007 12:06 AM

Joseph Gray wrote:

Are both machines syncing to the same ntp erver?
One or both of them of them hasn't synced to 127.127.1.0 by any chance?

Bruce

Although they are both using the pool at ntp.org, they are currently syncing
to different servers. They both are syncing to stratum 2 servers. Neither is
syncing to 127.127.1.0.

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Joseph

What are the actual IP addresses of the servers they are syncing to?

Bruce

Joseph Gray wrote: >> Are both machines syncing to the same ntp erver? >> One or both of them of them hasn't synced to 127.127.1.0 by any chance? >> >> Bruce >> > > Although they are both using the pool at ntp.org, they are currently syncing > to different servers. They both are syncing to stratum 2 servers. Neither is > syncing to 127.127.1.0. > > > _______________________________________________ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > Joseph What are the actual IP addresses of the servers they are syncing to? Bruce

ML

Maggie Leber

Thu, May 17, 2007 12:16 AM

On 5/16/07, Dr Bruce Griffiths bruce.griffiths@xtra.co.nz wrote:

What are the actual IP addresses of the servers they are syncing to?

Also check the "Internet Time" tab of the "Date and Time Properties"
dialog; it will tell you when the last time a successful sync was
done. If you have a firewalling router in between the PC and ntp.org
it might be blocking the sync.

--
Margaret Stephanie Leber CCP, SCJP SCWCD
maggie@voicenet.com http://voicenet.com/~maggie
AOPA 925383 -- Amateur Radio Station K3XS -- ARRL 39280 -- AMSAT 32844

"The art of progress is to preserve order amid change
and to preserve change amid order."-A.N.Whitehead

On 5/16/07, Dr Bruce Griffiths <bruce.griffiths@xtra.co.nz> wrote: > What are the actual IP addresses of the servers they are syncing to? Also check the "Internet Time" tab of the "Date and Time Properties" dialog; it will tell you when the last time a successful sync was done. If you have a firewalling router in between the PC and ntp.org it might be blocking the sync. -- Margaret Stephanie Leber CCP, SCJP SCWCD <maggie@voicenet.com> http://voicenet.com/~maggie AOPA 925383 -- Amateur Radio Station K3XS -- ARRL 39280 -- AMSAT 32844 "The art of progress is to preserve order amid change and to preserve change amid order."-A.N.Whitehead

JG

Joseph Gray

Thu, May 17, 2007 12:17 AM

What are the actual IP addresses of the servers they are syncing to?

Bruce

The one with the correct time:
Sync to: 64.5.1.130 Offset: 38.346ms Stratum: 3

The one with the wrong time:
Sync to: 24.123.66.139 Offset: -1.074ms Stratum: 3

> What are the actual IP addresses of the servers they are syncing to? > > Bruce The one with the correct time: Sync to: 64.5.1.130 Offset: 38.346ms Stratum: 3 The one with the wrong time: Sync to: 24.123.66.139 Offset: -1.074ms Stratum: 3

S

shoppa@trailing-edge.com

Thu, May 17, 2007 12:38 AM

"Joseph Gray" jgray@zianet.com wrote:

What are the actual IP addresses of the servers they are syncing to?

Bruce

The one with the correct time:
Sync to: 64.5.1.130 Offset: 38.346ms Stratum: 3

The one with the wrong time:
Sync to: 24.123.66.139 Offset: -1.074ms Stratum: 3

At my QTH both of those servers are Stratum 2 and within a few hundredths
of a second of the Right Time.

Odd that you see them as Stratum 3, maybe you've got a firewall pulling
tricks on you :-).

The best way to configure a NTP client is with multiple (preferably
3 or 4) servers, ideally nearby network-wise and diverse time-source
wise. It's pretty sad how almost all stratum 1's are locked to GPS
these days. If your NTP software doesn't support multiple servers,
it is REALLY REALLY a good idea to move to something that does...
hint: check out http://www.ntp.org/

Tim.

"Joseph Gray" <jgray@zianet.com> wrote: > > What are the actual IP addresses of the servers they are syncing to? > > > > Bruce > > The one with the correct time: > Sync to: 64.5.1.130 Offset: 38.346ms Stratum: 3 > > The one with the wrong time: > Sync to: 24.123.66.139 Offset: -1.074ms Stratum: 3 At my QTH both of those servers are Stratum 2 and within a few hundredths of a second of the Right Time. Odd that you see them as Stratum 3, maybe you've got a firewall pulling tricks on you :-). The best way to configure a NTP client is with multiple (preferably 3 or 4) servers, ideally nearby network-wise and diverse time-source wise. It's pretty sad how almost all stratum 1's are locked to GPS these days. If your NTP software doesn't support multiple servers, it is REALLY REALLY a good idea to move to something that does... hint: check out http://www.ntp.org/ Tim.

DB

Dr Bruce Griffiths

Thu, May 17, 2007 12:45 AM

Tim Shoppa wrote:

"Joseph Gray" jgray@zianet.com wrote:

What are the actual IP addresses of the servers they are syncing to?

Bruce

The one with the correct time:
Sync to: 64.5.1.130 Offset: 38.346ms Stratum: 3

The one with the wrong time:
Sync to: 24.123.66.139 Offset: -1.074ms Stratum: 3

At my QTH both of those servers are Stratum 2 and within a few hundredths
of a second of the Right Time.

Same here some 10,000+ km away

Bruce

Odd that you see them as Stratum 3, maybe you've got a firewall pulling
tricks on you :-).

The best way to configure a NTP client is with multiple (preferably
3 or 4) servers, ideally nearby network-wise and diverse time-source
wise. It's pretty sad how almost all stratum 1's are locked to GPS
these days. If your NTP software doesn't support multiple servers,
it is REALLY REALLY a good idea to move to something that does...
hint: check out http://www.ntp.org/

Tim.

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Tim Shoppa wrote: > "Joseph Gray" <jgray@zianet.com> wrote: > >>> What are the actual IP addresses of the servers they are syncing to? >>> >>> Bruce >>> >> The one with the correct time: >> Sync to: 64.5.1.130 Offset: 38.346ms Stratum: 3 >> >> The one with the wrong time: >> Sync to: 24.123.66.139 Offset: -1.074ms Stratum: 3 >> > > At my QTH both of those servers are Stratum 2 and within a few hundredths > of a second of the Right Time. > > Same here some 10,000+ km away Bruce > Odd that you see them as Stratum 3, maybe you've got a firewall pulling > tricks on you :-). > > The best way to configure a NTP client is with multiple (preferably > 3 or 4) servers, ideally nearby network-wise and diverse time-source > wise. It's pretty sad how almost all stratum 1's are locked to GPS > these days. If your NTP software doesn't support multiple servers, > it is REALLY REALLY a good idea to move to something that does... > hint: check out http://www.ntp.org/ > > Tim. > > _______________________________________________ > time-nuts mailing list > time-nuts@febo.com > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > >

JG

Joseph Gray

Thu, May 17, 2007 12:57 AM

At my QTH both of those servers are Stratum 2 and within a few hundredths
of a second of the Right Time.

Odd that you see them as Stratum 3, maybe you've got a firewall pulling
tricks on you :-).

The best way to configure a NTP client is with multiple (preferably
3 or 4) servers, ideally nearby network-wise and diverse time-source
wise. It's pretty sad how almost all stratum 1's are locked to GPS
these days. If your NTP software doesn't support multiple servers,
it is REALLY REALLY a good idea to move to something that does...
hint: check out http://www.ntp.org/

Tim.

They do show as stratum 2. That text is showing that my PC is stratum 3.

The Meinberg software is a Windows port of the NTP software. It is
configured to use three servers from the pool at ntp.org.

server 0.us.pool.ntp.org iburst
server 1.us.pool.ntp.org iburst
server 2.us.pool.ntp.org iburst

> At my QTH both of those servers are Stratum 2 and within a few hundredths > of a second of the Right Time. > > Odd that you see them as Stratum 3, maybe you've got a firewall pulling > tricks on you :-). > > The best way to configure a NTP client is with multiple (preferably > 3 or 4) servers, ideally nearby network-wise and diverse time-source > wise. It's pretty sad how almost all stratum 1's are locked to GPS > these days. If your NTP software doesn't support multiple servers, > it is REALLY REALLY a good idea to move to something that does... > hint: check out http://www.ntp.org/ > > Tim. They do show as stratum 2. That text is showing that my PC is stratum 3. The Meinberg software is a Windows port of the NTP software. It is configured to use three servers from the pool at ntp.org. server 0.us.pool.ntp.org iburst server 1.us.pool.ntp.org iburst server 2.us.pool.ntp.org iburst

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