In an am transmission the carrier wave is constant in frequency and varies in amplitude ( strength ) according to the sounds present at the microphone ; in fm the carrier is constant in amplitude and varies in frequency 在调幅的传播中,其负载电波频率是恒定的,但波幅(力度)随着麦克风声音变化而变化;在调频的传播中,其负载电波波幅是恒定的,而频率随着麦克风声音的变化而变化。