time-nuts@lists.febo.com

Discussion of precise time and frequency measurement

View all threads

Local System Time Sync

L-
Lee - N2LEE
Wed, Jul 26, 2017 2:45 AM

I have what I believe is a simply question. Especially for this illustrious brain trust. :)

How can I force Lady Heather to time sync the local computer system it is interfaced to ?

Isn’t this what the /ts[odhm] command accomplished or I am misunderstanding ?

  • Thunderbolt is interfaced to a Mac laptop running LH5
  • Connection is USB to Serial cable (might be the issue because of no PPS)
  • Turn off Internet NTP sync on laptop
  • Purposely set laptop time 15 seconds ahead
  • Enter / then after the dash(-) I enter tsm to sync system time every minute.

I thought this would force the system to sync ever minute with Thunderbolt time.
But it doesn’t it. It never corrects the laptop time, it is always wrong.

What am I missing here ?

Thanks,

Lee

I have what I believe is a simply question. Especially for this illustrious brain trust. :) How can I force Lady Heather to time sync the local computer system it is interfaced to ? Isn’t this what the /ts[odhm] command accomplished or I am misunderstanding ? - Thunderbolt is interfaced to a Mac laptop running LH5 - Connection is USB to Serial cable (might be the issue because of no PPS) - Turn off Internet NTP sync on laptop - Purposely set laptop time 15 seconds ahead - Enter / then after the dash(-) I enter tsm to sync system time every minute. I thought this would force the system to sync ever minute with Thunderbolt time. But it doesn’t it. It never corrects the laptop time, it is always wrong. What am I missing here ? Thanks, Lee
CA
Chris Albertson
Wed, Jul 26, 2017 4:23 AM

You should be using NTP for that.

Simply "syncing" the local clock to GPS is never the best thing to do.  If
you think about it 50% of the time the local clock would have to go
backwards and 50% forwards.  This means you could have the system time be
at the same time twice or you have missing time intervals.

The correct way is to adjust the RATE of the local clock so you never have
missing or double time.  This is exactly the same as building a GPSDO.
Every adjustment period you compare there PHASE of the local clock to GPS
then adjust the RATE if required.    NTP does this.

On Tue, Jul 25, 2017 at 7:45 PM, Lee - N2LEE via time-nuts <
time-nuts@febo.com> wrote:

I have what I believe is a simply question. Especially for this
illustrious brain trust. :)

How can I force Lady Heather to time sync the local computer system it is
interfaced to ?

Isn’t this what the /ts[odhm] command accomplished or I am
misunderstanding ?

  • Thunderbolt is interfaced to a Mac laptop running LH5
  • Connection is USB to Serial cable (might be the issue because of no PPS)
  • Turn off Internet NTP sync on laptop
  • Purposely set laptop time 15 seconds ahead
  • Enter / then after the dash(-) I enter tsm to sync system time every
    minute.

I thought this would force the system to sync ever minute with Thunderbolt
time.
But it doesn’t it. It never corrects the laptop time, it is always wrong.

What am I missing here ?

Thanks,

Lee


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.

--

Chris Albertson
Redondo Beach, California

You should be using NTP for that. Simply "syncing" the local clock to GPS is never the best thing to do. If you think about it 50% of the time the local clock would have to go backwards and 50% forwards. This means you could have the system time be at the same time twice or you have missing time intervals. The correct way is to adjust the RATE of the local clock so you never have missing or double time. This is exactly the same as building a GPSDO. Every adjustment period you compare there PHASE of the local clock to GPS then adjust the RATE if required. NTP does this. On Tue, Jul 25, 2017 at 7:45 PM, Lee - N2LEE via time-nuts < time-nuts@febo.com> wrote: > I have what I believe is a simply question. Especially for this > illustrious brain trust. :) > > How can I force Lady Heather to time sync the local computer system it is > interfaced to ? > > Isn’t this what the /ts[odhm] command accomplished or I am > misunderstanding ? > > - Thunderbolt is interfaced to a Mac laptop running LH5 > - Connection is USB to Serial cable (might be the issue because of no PPS) > - Turn off Internet NTP sync on laptop > - Purposely set laptop time 15 seconds ahead > - Enter / then after the dash(-) I enter tsm to sync system time every > minute. > > I thought this would force the system to sync ever minute with Thunderbolt > time. > But it doesn’t it. It never corrects the laptop time, it is always wrong. > > What am I missing here ? > > Thanks, > > Lee > _______________________________________________ > 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. > -- Chris Albertson Redondo Beach, California