[time-nuts] Can Lady Heather set PC time directly from a Trimble Thunderbolt?

Chris Albertson albertson.chris at gmail.com
Thu Aug 3 13:05:46 EDT 2017


This idea keeps coming up.   "Jamming" the time from a GPS into a
computer is NEVER the best idea.  When you "jam" the time the PC
internal clock moves in  jerks and jumps where it will move forward
and even backward.

The only way that works well is to discipline the PC's clock using the
same method you'd use to discipline the crystal inside A GPSDO.    You
compare the phase between the GPS and the local PC clock then adjust
the RATE of the PC clock to keep the peas in sync.   That is what NTP
does.

I say all of the above because this is a "timeouts" list.   If you
only care that the PC clock by "close enough" that the time printed on
the screen matches your wristwatch then a 50 millisecond error is
acceptable as that is about the limit of human perception.    But it
you are a "nut" and want each millisecond of time to be reasonably
equal, that means with "tick" of the PC's clock to advance in time
about the same amount then you can't "jam" the PC's clock from GPS.
You will need to adjust the PC clock's RATE not the PC clock's PHASE.

On Thu, Aug 3, 2017 at 6:54 AM, Chris Wilson <chris at chriswilson.tv> wrote:
>
>
>   03/08/2017 14:50
>
> I use an NTP client to set my Windows 7 64 bit PC time for digital
> mode amateur radio activities, but I was wondering if my Trimble
> Thunderbolt and Lady Heather can do the same job? If it can, how do I
> do it please, and can the PC show GMT and not UTC, and finally does
> the date glitch affect this? Lady Heather communicates with the GPS
> via a true serial port. Thanks!
>
> --
>        Best Regards,
>                    Chris Wilson. 2E0ILY
> mailto: chris at chriswilson.tv
>
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-- 

Chris Albertson
Redondo Beach, California



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