[ntp:questions] SIRF time output wobble, GPS or NTP fault?

unruh unruh at invalid.ca
Tue Mar 6 19:03:10 UTC 2012

On 2012-03-06, David J Taylor <david-taylor at blueyonder.co.uk.invalid> wrote:
>> Hi all,
>> I've been seeing some very strange behavior from my USB BU-353 GPS based 
>> on readings from the Meinberg Server Monitor.  The unit is based on the 
>> SIRF Star III e/LP chipset.  At first, I thought it was the GPS at 
>> fault.  But, now, I'm not so sure that it's not either NTP or the 
>> Meinberg monitor program.  Let me explain.
> []
>> Sincerely (confused),
>> Ron
> Ron,
> Sorry to be blunt, but please stop using serial NMEA output and expecting 
> good results!  If you see similar problems with PPS to the DCD pin of an 
> RS-232 port, please report them.

Since a 1 second error in nmea would also impact the PPS output, his
observation is far from irrelevant. That was what happened with the
Garmin 18x-- the nmea offset became greater than a second, and all hell
broke out. 

> Cheers,
> David 

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