The speed of a radio wave:

Radio waves are a form of electromagnetic radiation, exactly like visible light, ultraviolet, and X-rays. Because they are part of the same electromagnetic spectrum, they travel at the exact same speed in a vacuum: approximately 300,000 kilometers per second (the speed of light). This speed is a universal constant for all electromagnetic waves in free space. It does not vary based on the frequency or wavelength of the signal being transmitted. While the speed can slow down slightly when passing through physical mediums like coaxial cables (the velocity factor), in the context of general wave propagation through space, it is universally equal to the speed of light.