[time-nuts] Next step up from basic GPS/PPS timekeeping

Bob Camp kb8tq at n1k.org
Wed Feb 24 17:50:09 EST 2016


Hi

If you are looking at pool service, the first question would be how you connect to the backbone. 

If you are running something asymmetric (DSL / cable modem) you already have enough of an 
offset that it alone it far bigger than any other error in your system. Even with fancier connections,
asymmetry can be an issue. 

Next thing to look at is how heavily loaded your connection becomes. A lot of links have limited 
bandwidth in both directions, but traffic loads that are much heavier in one direction. It does not
take much single direction buffering to take that up to a significant level.

Bob

> On Feb 24, 2016, at 9:22 AM, Neil Green <ncguk at hotmail.co.uk> wrote:
> 
> I currently operate a stratum 1 NTP server in the NTP pool using a U-Blox Max-7Q GPS module with PPS attached to, variously, a Raspberry Pi via GPIO or a Celeron mini PC via serial DB-9. The machine does nothing but serve time to the pool. Operating systems of choice are Debian or FreeBSD.
> 
> 
> What would be my next step up be, hardware-wise, in terms of improving precision, stability, etc? A GPSDO? Budget is limited as far as these things go - about £150 UK/$210 US.
> 
> 
> I appreciate this is basic stuff compared to the usual discussions but this doesn't seem the right question to ask on the NTP lists. Any help appreciated. Thanks.
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