Michael Coslo wrote:
Jim Lux wrote:
K7ITM wrote:
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.

Which was the original intent of my comment. Fat radiators are
shorter at resonance than thin ones, and the details of why are not
simply explained by something like "capacitance effects", although
such an explanation may sort of work over a limited range.

Sorry, been away for a while, but I'm back.

Certainly the capacitance may play some small part. But does added
capacitance increase bandwidth to the extent - or at all - that is
achieved by the cage or very thick dipole?

Nope.. that's why "increased capacitance" is a bad model.



Richard Harrison's reference to Baily regarding velocity is interesting.
Why would the velocity be less at increased width? And would that
increase the Bandwidth?

larger C per unit length makes 1/sqrt(LC) smaller
no for the BW