[ntp:questions] UTC Time from NMEA receiver one second behind DCF?

David J Taylor david-taylor at blueyonder.neither-this-bit.nor-this-bit.co.uk
Tue Aug 12 11:49:48 UTC 2008

Venu Gopal wrote:
> David J Taylor wrote:
>> Venu Gopal wrote:
>>> I have a couple of similar experiences !
>>> I observed that the NMEA sentences are not generated in sync with
>>> PPS. Theres lot of jitter in these sentences resulting in 1 second
>>> offsets. Its fine if the jitter is within few milliseconds. But
>>> sometimes it exceeds a second and thats really painful.
>>> This observation was discussed earlier and the solution is to go for
>>> a better GPS receiver!
>> Use the shortest GPS sentences, and the highest baud rate, to keep
>> the total message time as short as possible.
> The issue is not with the length of the messages and the baud rate.
> Venu

Well, I found that if you had a bad configuration (sentences too long or 
baud rate too low), the sentences could exceed one second, and therefore 
be useless for NTP.

However, I have not made any measurements showing jitter versus sentence 
length, so I would appreciate any pointers to measurements you have made 
or know about.


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