[ntp:questions] Questions about joining pool.ntp.org

David Woolley david at ex.djwhome.demon.invalid
Tue Aug 30 06:54:50 UTC 2011

NPG wrote:

> I'm not sure what "cable length", "speed of light delay", or "velocity
> factor" is all about.

It's a basic tenet of modern physics that information cannot travel 
faster than the speed of light.  That applies not just in free space, 
like radio waves, but also in cables.  In practice, the information 
travels at less than the speed of light in cables, and the ratio is 
called the velocity factor, and for coaxial data cables can be about 
2/3rds of the speed of light.

(Strictly speaking, information in cables is a guided radio wave in the 

> A real propagation failure would be when the signal never got there.

Or got there by a longer path than expected, or so as to interfere with 
itself, One particular failure is where sharp pulses get smeared out.

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