[SI-LIST] Re: SMA cable for TDR

> Are you really talking about dispersion or skin effect?

Tom,

Maybe I'm getting a bit sloppy, but I consider them to be related.

In a generic sense, I have used often "dispersion" to encompass
frequency-dependent effects - including group delay and attenuation,
which agrees with Merriam-Webster's definition "the scattering of the
values of a frequency distribution from an average."  That said, I
realize that many people use dispersion specific to group delay and not
to include frequency-dependent attenuation.

If we look at "skin effect," however, we note that it influences both
the distributed resistance and distributed inductance of a transmission
line - both of which impact group delay.  As such, I contend that skin
effect is one factor in group delay, which is then a factor in
dispersion.

Dielectric properties are also a factor in group delay and hence
dispersion, so skin effect is not the sole issue.  However, I generally
do not separate the two, and use "dispersion" in a broader sense of
all-things-frequency-dependent.

As for the cable discussion of this thread, we have not taken the effort
to separate out dielectric versus metallic effects, but we are fairly
confident that metallic effects (i.e., skin effect) dominate over
dielectric effects in the cables/applications we have traditionally been
interested in.

Pat

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