On Feb 11, 6:04*pm, Roy Lewallen wrote:
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?

Yes.

I mean the more L and C you have per meter of line the lower the
signal velocity, right?

Right.

How much is the signal speed retarded by typically and are there any
circumstances where we need to be concerned about this phenomenon?

The velocity factor for air dielectric cables is essentially unity. The
slowest common velocity factor is about 0.66, which you'll find in coax
(where the field is entirely in the dielectric) having solid
polyethylene dielectric. Velocity factor is important in determining the
physical length of cable needed to effect a specific time or phase delay.

Roy Lewallen, W7EL

it is also important when you try to get cables to reach a certain
distance and still be a given phase length. this is why foam coax is
specified for 1/4 wave lines feeding most 4-square vertical systems.
a solid dielectric line 1/4 wave long is too short to reach from the
center to the feedpoints.