What happens as the frequency of a signal in coaxial cable is increased?

All coaxial cables experience signal attenuation, or loss, as RF energy travels through them. This loss is primarily caused by conductor resistance (aggravated by the 'skin effect' at higher frequencies) and the absorption of energy by the cable's dielectric insulator. As the frequency of the transmitted signal increases, both of these loss factors become more pronounced, resulting in greater overall signal loss. The characteristic impedance of a coaxial cable (such as 50 or 75 ohms) is a physical property determined by the diameter of the internal and external conductors and the type of dielectric material used. Because it is dictated by the cable's physical construction, the characteristic impedance does not change when the signal frequency is increased or decreased, making those options incorrect.