On Feb 11, 7:59*am, phaedrus wrote:
Just need to get these things clarified!

The velocity factor of a tx line is governed by its distributed
inductance and capacitance, is it not?
I mean the more L and C you have per meter of line the lower the
signal velocity, right?
How much is the signal speed retarded by typically and are there any
circumstances where we need to be concerned about this phenomenon?

Something not mentioned by other replies I've seen: some transmission
lines are made specifically to get delay. They are generally called
delay lines. Typical construction is to use a helical coil for the
center conductor, to increase inductance per unit length.

In straight TEM transmission line (typical coax), the propagation
velocity is the same as the speed of light (or more properly of
electromagnetic radiation of the same frequency) in the dielectric.
For any dielectric I've seen used in transmission lines, that's just
free-space speed of light times 1/(relative dielectric constant) of
the dielectric. If the magnetic properties of the dielectric differ
from those of a vacuum, you also have to consider that.

You need to consider velocity factor any time you're concerned with
the phase shift of the signal propagating through the line: phasing
lines for antennas, impedance measurements made by an instrument at
one end of the line of the impedance of a load at the other end of the
line, how long it takes a signal to propagate over the line, ...

Cheers,
Tom