How is the outer protection of a co-axial antenna cable structured?

The outer protection of a co-axial antenna cable is made of a protective insulator, which serves multiple purposes. This protective insulator is crucial for safeguarding the inner conductor and dielectric layers from physical damage, environmental factors, and electrical interference. It also provides a barrier against moisture and other contaminants that could otherwise compromise the cable's performance.

The protective insulator's role is significant as it allows the cable to maintain the integrity of the signal transmitted through the inner conductor while preventing unwanted interference from external sources. This structure ensures that the co-axial cable can function optimally in various operating environments, which is particularly important in avionics applications where electromagnetic interference needs to be minimized for reliable communications and navigation.

While other structures such as additional layers of dielectric or multiple insulation layers can be found in different cable designs, in a typical co-axial antenna cable, the outer layer primarily serves as a protective insulator, encompassing the inner workings but not serving additional functions like those implied in other options.