Coaxial is a term derived from the construction of the cable, as illustrated here. In a coaxial cable an electrical impulse signal is transmitted along the cable length between the center conductor and the outer conductor. The center conductor and the outer conductor share the same center line or axis hence the term coaxial.
Shielding Effectiveness is the relative ability of a shield to screen out undesirable interference. In coaxial cable, the outer conductor provides a shield to keep interfering signals from getting in and to keep signals from leaking out to become undesirable interference for nearby devices. Shielding Effectiveness is measured in dB with higher values indicating better shielding properties. The table below illustrates the relative shielding properties of various shielding types.
Notice as the shielding density increases there is a correlated increase in the shielding effectiveness value. The best shielding effectiveness value can be found in a rigid coaxial cable due to the solid tube construction of the outer jacket. In this type of cable the limiting factor for shielding effectiveness is the quality of the connector attachment.