# EM Waves in Coaxial Cable

I've been educated that a coaxial cable has two conductors: inner or the central core and the outer conductor or the sheath. Both these carry currents but in opposite directions. The AC current produces Electromagnetic radiation that propagates in the form of a wave. The energy or the information(intelligence) is carried by the Electric and Magnetic fields. My query is that whether the EM waves propagate between the inner and the outer conductor or inside the inner copper (clad with steel) conductor? If so, does the EM wave travel along the dielectric insulation between the inner and outer conductor?

Ron Schmitt's "Electromagnetics Explained" tells that EM waves travel between the wires and not inside the wires. Does this also apply to a coax cable?

• Yes, it is between the conductors. But it is oversimplification. Mathematically speaking, the wave is everywhere. Conductors are needed to impose the boundary conditions on the wave equation describing it. Commented May 25, 2017 at 17:27
• fields INSIDE the metal are approximately 1,000,000X slower than fields on the surface. Measuring between two loops of metal, inserting 1.4mils of copper on FR-4, there is 150 nanoseconds of delay shown on the scope. Plus lots of attenuation. This was for 20 nanosecond squarewave. Commented May 25, 2017 at 17:34
• It should be stated that the waves in a coax cable are TEM. That is, transverse to the direction of propagation. Commented May 25, 2017 at 22:03