[time-nuts] Project on precise timing over Ethernet

Hal Murray hmurray at megapathdsl.net
Fri Sep 11 18:02:26 UTC 2009

> Actually, you can see this as a Shannon information channel, analog or
> digital.

What sort of bandwidth do I need to run a PLL over a long link?

I assume it takes enough to cover all the sources of error:
  drift in the master
  drift in the local oscillator
  drift in the communication link

Does it depend on my target accuracy?  Do I need more or less bandwidth for a 
better answer?  Am I even asking a sensible question?

What sort of changes in delays to I get on 10 km of fiber or coax or twisted 
pair?  Is temperature the only interesting variable?

Can I measure tides with a 10 km link?  Or is that swamped by temperature?

How about microwaves?  Does the speed of light in air change with temperature 
or humidity or whatever?

What's the final bandwidth out of the control loop on something like a GPSDO?

These are my opinions, not necessarily my employer's.  I hate spam.

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