[ntp:questions] ESR looking for good GPS clocks

David J Taylor david-taylor at blueyonder.co.uk.invalid
Wed Mar 7 08:35:52 UTC 2012

"Ron Frazier (NTP)" <timekeepingntplist at c3energy.com> wrote in message 
news:4F566EBD.2020703 at c3energy.com...
> On 3/6/2012 11:00 AM, David J Taylor wrote:
>>  http://www.satsignal.eu/ntp/Garmin-GSP18x-LVC-firmware-issue.htm
>>  http://www.satsignal.eu/ntp/Garmin-18x-3.7.png
> I looked at that chart 3 times and even zoomed in on it.  It looks like 
> to me that the vertical scale is in ns.  So, the variation in start time 
> for the NMEA sentence is about 170 ns if I'm reading it right, not ms. 
> In that case, it's about 2/10 of a us.  This would have little impact 
> compared to the 170 ms of possible variation we're discussing.

It's milliseconds.

>> The table here:
>>  http://www.satsignal.eu/ntp/Garmin-18x-3.7.png
>> lists two SiRF devices with a claimed 1 us accuracy.  PPS, not NMEA.

> I think that may be the wrong link.  I can't find any devices listed 
> there.

Indeed!  <G>  Please see:



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