Radio transmission
The amplitude modulation radio broadcast is divided into three large bands of long wave, medium wave and short wave, which are respectively transmitted by radio waves of corresponding bands. There are only two large-band radio broadcasts in China and shortwave. The frequency band used by medium wave broadcasting is roughly 550 kHz-1600 kHz, mainly relying on ground wave propagation, and is also accompanied by partial sky waves; the frequency band used by short wave broadcasting is about 2 MHz-24 MHz, mainly relying on sky wave propagation, and ground wave in close range. The FM radio broadcast uses ultra-short-wave (very high-frequency) radio waves to transmit signals at a frequency of about 88 MHz to 108 MHz, and mainly transmits signals by spatial waves. At present, terrestrial broadcast television is divided into two frequency bands: VHF (very high frequency or meter wave) and UHF (extra high frequency or decimeter wave). In China, the frequency range of TV used in VHF band is 48.5MHz-3MHz, which is divided into 1-12 channels. The frequency range used by UHF band is 470MHz-956MHz, which is divided into: 3-68 channels. They basically rely on space waves to propagate. The internationally specified satellite radio and television has six frequency bands, the main frequency band is 12kMHz, which is also transmitted by space.
