Ground wave
The electric wave which is transmitted through the terrestrial (ちじょうは) ground. I am used as an antonym of the satellite wave.
Spread
With the diffraction wave to diffract in a reflection wave, the ground, the topography, a building to reflect other than a wave directly in the ground, the topography, a building that the ground wave is an electric wave transmitting between ground two points and arrives at directly (of course there are the waves to reflect it, and to diffract).
I put the most important one together by a direct wave and an earth reflection wave to reflect in the ground, and it is said with an air wave. The aerial wave damps by reversely own square of the distance and does not reach it when I exceed the horizon and an obstacle again.
I say the ground wave, and the earth diffraction wave to diffract in the ground is particularly important by medium frequency (AM radio). The earth diffraction wave (ground wave) damps with the reverse fourth power of the distance rapidly, but reaches it than an aerial wave to the distant place because the horizon is gone over.
The wave to reflect at the ionosphere is called an ionosphere wave. But I do not include the ionosphere wave in ground wave closely. It is important by a short wave (shortwave) and night medium frequency. It reaches it very far and wide that the ionosphere wave damps with reverse one vehicle of the distance only gently and goes over the horizon again.
Because diffraction is weak, and an ultra-short wave (FM radio, VHF TV), the ultra high frequency (UHF TV) does not do the ionosphere reflection either, it does not reach the other side of the horizon. For the obstacle, a reflection wave with the mountains, the building may arrive, but the electric field strength becomes weak. I often receive it with a high-performance antenna (as for the UHF Pallas tuck antenna) unless an electric field strength is very weak.
Broadcast
Broadcast using ground wave is called terrestrial broadcasting. A transmitting station is approximately synonymous with broadcast in the ground above the ground. It is used as an antonym of the satellite broadcasting, and it is common closely average, that the shortwave broadcasting includes in terrestrial broadcasting conveniently that I use the ionosphere reflection wave. Because there was only terrestrial broadcasting as for the early period of broadcast, TV, a radio are higher in the diffusion rate than satellite broadcasting together.
Generally, I broadcast it using the frequency of a VHF Zone or the UHF Zone (in parts of the fringe area where reception is poor an SHF Zone) from the antenna of the transmitting station installed in the good mountaintop of the prospect and the expensive broadcasting tower.
Satellite broadcasting is limited to the neighbor of the range where the area that I can receive sees the antenna of the transmitting station by the terrestrial broadcasting whereas an electric wave of the about the same strength is sent to national ... supranationality area (when Japan nationwide). In addition, an electric wave becomes weak, and it is necessary for even the area of the metropolis and districts scale to put up plural antennas in the mountains by the weak ultra-short wave, ultra high frequency broadcast of diffracting in particular it as it goes away from the transmitting station.
On the other hand, there is relatively little limitation of a position and the direction of the receiving antenna whereas most of the satellite broadcasting uses the reflection, SHF wave not to diffract because there are a reflection and diffraction by the terrestrial broadcasting. In addition, it depends on frequency and electric wave strength, but may receive it with an antenna of the size that I can carry that is smaller than satellite broadcasting.
Allied item
This article is taken from the Japanese Wikipedia Ground wave
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