Hello Roy!

Roy Lewallen wrote:

The transmission line velocity factor applies only to the inside of the
coax, where the fields are entirely within the dielectric material.
Waves on the outside of the shield are propagating at nearly the speed
of light. A jacket will slow propagation by somewhere around 2 - 3%.

Great. Makes sense now.

It's not apparent why you need to worry about the exact electrical size
of the loop anyway, unless you're trying to predict with good accuracy
how much tuning C you'll need.

Well, I was thinking about trying to maximize the area surrounded by the
loop up to about 1/10th of a wavelength or so. What I found was that
the distributed capacitance of my cable at this length was too much for
my tuner to handle. So when I multiplied this length by my cable's
velocity factor, 0.66, suddenly the tuner could handle it and the loop
came alive! THIS is what got me on the wrong path thinking that the
center conductor was the antenna, and that I had discovered some
overlooked secret about the velocity factor. I was obviously mistaken.

Actually, you're pretty close. The current simply flows around the edge.
It might help to visualize the shield as being hollow, with a separate
inner and outer "shell", connected only at the cut end of the gap.

Right. Kind of like a hollow knife blade. You've got two physical
sides that meet at a cutting edge, but if you examine it closely, you'll
see that we are only really dealing with one outer conductive surface
"folded" so to speak back on itself. The edges of the exposed gap wires
represent the cutting edge - a small distance to be sure, but it is a
length of conductive material making a seamless join. Two sides, but
one surface.

Thanks again for the help.

73
Brian