Thanks, all, for your helpful responses.

The general consensus appears to be that a tiny electric dipole will be
induced that oscillates transverse to the cable at the same frequency
as the carrier. It might possibly leak a tiny amount of energy to the
area immediately surrounding the coax, but probably not a significant
amount compared to that which is already lost due to imperfections in
the cable.

I'm not planning any installation in an MRI, but I do have an
application where the cable is routed through some fairly strong
permanent magnetic fields, and I wondered if I needed to magnetically
shield the cable to avoid substantial losses. Sounds like I don't need
to worry.

I suppose I could actually run a test, but it's a lot easier just to
freeload off all your experience!

Tracy Hall
hthalljr'gmail'com