paulkoning at comcast.net
Fri Feb 3 13:51:39 CST 2017
> On Feb 3, 2017, at 2:43 PM, Tony Duell <ard.p850ug1 at gmail.com> wrote:
> On Fri, Feb 3, 2017 at 7:35 PM, Mouse <mouse at rodents-montreal.org> wrote:
>>>> the propagation delay as the signal gets to each pin (remember a
>>>> foot is about a nanosecond. [...])
>> Not really. A foot is about a light-nanosecond, yes, but
>> high-frequency signals in copper travel by skin effect, moving
>> significantly more slowly - somewhere around .6c, I think it is.
> It's not really the skin effect that matters here. It's the dielectric
> medium that surrounds the conductors that effectively slows the
> fields down.
Yes. Consider open wire transmission line, which has a velocity factor around 98%. Or air dielectric coax, similarly high value. The smaller numbers. like 66%, are found in traditional solid-dielectric (not foam) coax cable.
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