Propagation speed of radio signal

The propagation speed of radio signals in air is slightly less than the speed of light, usually about equal to the speed of light. It is about equal to 299,792,458 m/s, and the essence of radio signal is electromagnetic wave.

The propagation speed of radio waves in other media is Vε=C/sqrt(ε). Where ε is the dielectric constant of the propagation medium. The dielectric constant of air is very close to that of vacuum, slightly greater than 1, so the propagation speed of radio waves in air is slightly less than the speed of light, which is generally considered to be equal to the speed of light.

Radio signal propagation modes: direct, reflection, refraction, penetration, diffraction (diffraction) and scattering. For free space, because there are no obstacles in free space, the propagation of radio waves is only direct, and there is no other phenomenon.

Extended data

There are three main propagation modes of radio waves from the transmitting place to the receiving place: sky wave, ground wave and spatial linear wave. The characteristics of each wave are as follows:

1. Ground wave: The electric wave propagating along the earth's surface is called ground wave. In the process of propagation, because the radio wave is absorbed by the ground, its propagation distance is not far. The higher the frequency, the greater the ground absorption, so when short wave and ultrashort wave propagate along the ground, the distance is close, generally not more than 100 km, while the medium wave propagation distance is relatively far.

2. Sky wave:

Radio waves propagated in the atmosphere by ionospheric reflection are called sky waves, also known as ionospheric reflection waves. The transmitted radio wave reaches the receiving place after being reflected by the ionosphere 70-80 km above the ground, and its propagation distance is far, generally above 1000 km. The disadvantage is that it is greatly influenced by ionospheric climate and the propagation signal is very unstable.

3. Spatial linear wave: The electric wave that propagates linearly from the transmitting place to the receiving place in space is called spatial linear wave, also called linear wave or line-of-sight wave. The propagation distance is within the line of sight, only a few tens of kilometers. The walkie-talkies and radars equipped by fishing boats are all devices that communicate by means of space wave propagation.

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