[ntp:questions] Something for distributing a PPS signal?

David J Taylor david-taylor at blueyonder.co.uk.invalid
Sat Jul 2 05:51:27 UTC 2011


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<Null at BlackList.Anitech-Systems.invalid> wrote in message 
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> Unless I'm off by a magnitude somewhere;
>
>  Copper wire is about 0.3m/ns? 100m ~= 333+ns?
>
> The differences in e.g. PC serial port implementations
>  between different PPS recipients may easily cause a
>  difference of that much.

You are missing the velocity factor of typical cable, which slows the 
signal down to 5ns/m (round figure).  But it doesn't affect your basic 
argument that cable delays are insignificant compared to different 
hardware implementations, not to mention differences in OS interrupt 
latency and response times.

Cheers,
David 




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