By Robert S. Powers, Federal Communications Commission
A prime advantage of coaxial cables for telecommunications purposes is that signals carried on such cables will not, in principal, interfere with signals carried over-the-air or on other cables. Thus, the same frequency spectrum may be used many times without the necessity of spectrum coordination. This advantage exists, of course, only to the extent that the space inside cables is in fact electromagnetically separated from free space. To the extent that cable systems do "leak" signals, other measures have to be taken to assure non-interference with over-the-air radio services, particularly those radio services related to safety of life and property.
This paper will address how leaks can occur, what fields can be produced, circumstances under which interference can occur, and how interference can be prevented.