[mythtv-users] Way OT: High-speed Data Service Delivery

David Watkins watkinshome at gmail.com
Wed Jul 13 11:20:08 UTC 2011

>>Sorry for diving in a bit here, and apologies for my ignorance, but
>>surely the propagation speed over copper is approx the speed of light,
>>and over fiber it /is/ the speed of light (in whatever medium the
>>fibre is made of?)
> The NVP (nominal velocity of propagation) for a copper pair is
> typically in the order of 70% of the speed of light in a vacuum. When
> testing copper cable, to get an accurate length you need to set the
> NVP in the tester - either by using a manufacturers figure, or by
> testing a sample of cable.
> And for fibre, yes you are correct.

... which also happens to be approximately 70% of the speed of light
in a vacuum.

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