I just bought the radio and received CCTV-1., and the sound is the same, but some radios are not available. What's the matter?
Amplitude modulation (medium wave, short wave) radio can not receive the television sound.But now, some manufacturers in order to make the radio radio to receive television sound, specially designed for the production of a variety of frequency ranges including all or part of the radio frequency channel television sound, and some even include not only the standard television channels, including additions (cable TV special) TV channel sound. You can get a TV sound with this radio.
Sound broadcasting is divided into amplitude modulation broadcast (medium wave, short wave) and FM broadcasting (FM). The principle of FM broadcasting is the same as that of the TV sound, which is frequency modulated wave propagation. The frequency is 88 - 108MHZ, and there are also 70 - 108MHZ (including the so-called campus broadcast frequency). The frequency of the audio on TV channels is no longer in the audio broadcast FM band. Perhaps in the region of your CCTV1 channel, the frequency of the audio frequency falls into the audio broadcast band, which can be received by FM radio.
The TV program is in the form of sound wave frequency modulation in the TV signal, on the TV after the circuit is separated by amplifying circuit and then sent to restore the sound horn. After receiving the sound broadcast signal, the radio is amplified by the amplifying circuit, and the sound is restored by the loudspeaker.
