On Oct 20, 5:57*pm, Jim Lux wrote:
....
Some might argue, though, that the reason the effective velocity is less
is because the sqrt(1/LC) term is smaller because C is bigger because of
the increased surface area. *And that might not be far from the truth
for a restricted subset of antennas.

On the other hand, the propagation velocity of coaxial cable of
constant outer conductor ID is independent of the inner conductor
diameter, even though the capacitance per unit length increases as the
inner conductor diameter is increased. Clearly one must be careful
about attributing the effect to a single cause like increased
capacitance.

I haven't noticed in this thread any reference to Ronold W. P. King's
work. His writings should give more insight into the subject, if you
can get deeply enough into them. It's discussed empirically in
"Transmission Lines, Antennas and Waveguides," (with lots and lots of
interesting graphs showing the effect from various viewpoints) but you
can probably go deeper into the theory than you need in his other
books and papers on linear antennas.

Cheers,
Tom