Coaxial cables conduct electrical signals using solid, stranded or copper-plated steel wires (referred to as center conductors or cores) that are surrounded by an insulating layer (dielectric) that is shielded and protected by an outer insulating sheath. The function of the dielectric is to maintain the spacing between the shield and the center conductor, but a certain amount of signal energy is dissipated in the dielectric material itself. When an electric field is applied, the ideal dielectric material does not have electrical conductivity, but all dielectrics have a certain degree of measurable electrical conductivity.
Temperature stability is important for maintenance to measure and regulate the performance of the coaxial cable. If the temperature of the coaxial cable rises too high or too fast, the cable may warp and be damaged and cannot be repaired. Since any heat generated by dielectric loss dissipates within the dielectric, it is critical to consider the structure of the dielectric material when selecting the correct cable for a particular application.
The most common dielectric material is polytetrafluoroethylene (PTFE), which has a lower dielectric loss than PVC. The benefit of using PTFE is that the material can withstand temperatures from -50 ° C to + 200 ° C and is often used in combination with other materials to increase the dielectric constant or improve temperature stability. A disadvantage of this material is that it is sensitive to moisture under voltage stress.