About classical electrodynamics
This article develops from my 1967 article
"Crosstalk (Noise) in Digital
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important to not get bogged down in the mathematics, which could have been
omitted. Initially, skim through the maths in the second column, which
merely proves that a signal travelling down a coaxial cable sees ahead 50
ohms and travels at the speed of light for the dielectric. Avoid the third
column; “Crosstalk in Digital Systems”, which is merely an extension of the
previous maths, but deals with more conductors and shows that whereas in a
coaxial cable a single impedance and single velocity is permissible, in the
case of more wires, more “modes” are possible. The mathematics is very
similar to what went before, but more complicated, now involving not only
self inductance, but also mutual inductance. Try to assume, initially, that
complicated mathematics proves two impedances and two velocities rather
than only one in the case of coax.
point, look at the photographs, Figure 3 for visual proof of the two “modes”,
and so bypass the mathematics.
that Figure 4 is an idealised version of Figure 3. A plane wave front is
advancing at the speed of light guided by the conductors. It begins at the
third trace, then advances 3 metres to the second trace, then another three
diagramatically clarifies the waveforms.
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