Explanation: Glazed porcelain is ideal due to its excellent dielectric strength, which means it can withstand high voltages without breaking down. It also has very low dielectric loss, minimizing the absorption of RF energy from the antenna. Crucially, the glaze provides a smooth, non-porous surface that resists water absorption and contamination, preventing surface leakage currents and maintaining its insulating properties even when exposed to rain, dirt, and UV radiation over many years. Graphite composites are unsuitable because graphite is an electrical conductor, not an insulator. Rubber degrades significantly under prolonged UV exposure and weathering, losing its elasticity, becoming brittle, and compromising its insulating capabilities. While glass is a good insulator, glazed porcelain often provides superior long-term resistance to surface contamination and offers greater mechanical ruggedness for strain applications in harsh outdoor environments.