[time-nuts] Newbie questions
hmurray at megapathdsl.net
Wed Jan 6 07:48:50 UTC 2010
magnus at rubidium.dyndns.org said:
> This sounds fast. The normal taxiometer is at 66% of speed of ligth in
> vaccum, which for 1 ns is about 3 dm so for the RG-59 that would be
> about 2 dm.
> Some cables reach 78%, but RG-58 and RG-59 is down at normal 66%.
My rule to thumb for back-of-envelope work is that a signal in fiber and good
(but not nutty) coax goes 1 km while light in air/vacuum goes 1 mile. In
this context, "good" means foam rather than solid dielectric.
Light goes 1 ft/ns in air or 5000 ns per mile or 5 usec/mile. In coax/fiber,
that's 5 usec/km.
These are my opinions, not necessarily my employer's. I hate spam.
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