What is a disadvantage of air core coaxial cable when compared to foam or solid dielectric types?

Air core coaxial cable utilizes air as the primary dielectric insulator between the center conductor and the outer shield, often with a spiral plastic spacer to keep the conductor centered. Because the cable is largely hollow inside, any moisture or water that enters can travel along its length, which alters its impedance and drastically increases signal loss. To prevent moisture contamination, special techniques like pressurizing the cable with dry air or inert gases (such as nitrogen) are required. In contrast, foam or solid dielectric cables are completely filled with insulating material, inherently blocking moisture from migrating inside the jacket. Distractors regarding loss or frequency limitations are incorrect. In fact, air core cable generally has lower loss per foot than solid dielectric types, which is its primary advantage for VHF and UHF applications.