[time-nuts] T.I. experimenting - newbie question
Mike S
mikes at flatsurface.com
Sun Apr 3 11:56:56 UTC 2011
At 09:42 PM 4/2/2011, Joseph Gray wrote...
>I'm reading 18.9 ns. The coax specs give a VOP of 66%. This should
>calculate out to a length of 3.74 M. When I measure the coax, I get
>3.8 M.
Your calculation is incorrect. If the velocity factor only has 2
significant digits, the result of the calculation can only have 2
significant digits. And, I doubt the coax manufacturer will guarantee
the VF to 1 part in 66.
VF is the reciprocal of the square root of the dielectric constant of
the coax insulator. 66% implies you're using a cable which uses solid
polyethylene. A quick google for the dielectric constant of
polyethylene shows a range (2.2-2.4 depending on the source). That
would be a VF range of .67-.65.
Working your numbers, I get a length of 3.7-3.8 m.
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