FM is FM stereo with the best sound quality and can only receive local signals. Moreover, FM means that the frequency of high-frequency carrier is not a constant, but a modulation mode that changes with the modulation signal in a certain range, and its amplitude is a constant. So the signal is relatively stable.
AM is medium wave, with second sound quality, and can receive long-distance signals. AM refers to amplitude modulation, which is an electrical signal that changes from the height of sound to the amplitude. It is far away from us and is greatly influenced by weather factors. Suitable for provincial radio broadcast.
Therefore, in order to ensure the stability of the broadcast of CET-4 and CET-6, the school will adopt FM to announce the frequency before the exam, so as to facilitate the audition in advance and ensure the smooth progress of the exam.
Extended data:
Extended data:
Main functions and uses of FM headphones
1, FM wireless headset. FM wireless headset, specially designed for senior high school entrance examination, college entrance examination and CET-4 and CET-6.
2. Dual FM receivers, FM 1 is the special frequency band for hearing test, and FM2 is the special frequency band for FM radio. Students can listen to news, music and other radio programs in their spare time.
3, internal circuit materials, fine production, clear sound quality, loud voice, high sensitivity and good selectivity. It is the best choice for foreign language listening test.
References:
Baidu encyclopedia -FM headset