Cecil. W5DXP wrote:
"When 600 inches of wire is coiled into a helix, how can EM waves travel
through that 600 inches of wire faster than it can travel through 600
inches in free space?"

Good question. Maybe it figuratively travels from both ends of the coil
toward the niddle. At one part of the cycle the wave is pushing excess
electrons to one end of the coil while it supplies electron deficient
atoms to the other end. Then the cycle reverses the charge situation at
the ends of the coil. Or maybe the photons do blast off to leap across
the length of the coil. My vision isn`t good enough to see what is going
on inside of the coil`s conductor.

Best regards, Richard Harrison, KB5WZI