An old style copper ladder line is ~0.95c and optical fibre is ~0.66c: Old style, pre-coaxial, undersea cables may have been ~0.45. Newer coax is sometimes ~0.

An old style copper ladder line is ~0.95c and optical fibre is ~0.66c: Old style, pre-coaxial, undersea cables may have been ~0.45. Newer coax is sometimes ~0.87c. YMMV: https://meanderful.blogspot.com/2017/05/lines-radios-and-cables-oh-my.html https://meanderful.blogspot.com/2017/05/lines-radios-and-cab...