[Pool] Score is drop in cycles

David J Taylor david-taylor at blueyonder.co.uk
Fri Feb 21 09:44:24 UTC 2014

From: Jeff Woolsey

Not necessarily.  Trust but verify your local reference clock against
other servers out there.  For example, I'm currently seeing about 60ms
of jitter/offset in the SHM refclock from gpsd managing a SiRF II
device.  (It was 10 seconds off before I fixed gpsd not to request
messages it's ignoring anyway.).  It's USB, but still I'd expect only
1-2ms of offset/jitter, which is fine for my purposes:

Are you using PPS?  The serial data alone may typically be no better than 
Internet servers, and may be worse if you have a good Internet connection. 
PPS even over USB will be significantly better.  PPS with a direct 
connection should be much better - I'm seeing microsecond offsets on my 
Raspberry Pi cards with a variety of GPS receivers - all rather low-cost!



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Email: david-taylor at blueyonder.co.uk 

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