I know I read about this in the NCTI course many years ago. If I remember all signals pass along the outer part of the center conductor on the copper cladding.
The only thing that I could find was this link: http://www.pelco.com/support/videosecbasics/cableoverview.aspx
If you need additional info PM me with your FAX number and I will try to find my old NCTI book a fax that page to you.