1. Frequency difference
FM = Frequency Modulation FM, microwave; microwave transmission, high signal quality, low transmission cost, low transmission power, small coverage area, greatly affected by geographical factors, generally used as the first choice for urban broadcasting. For example, your hometown city station can generally be listened to via FM.
AM = Amplitude Modulation Amplitude Modulation, Microwave; Medium Wave transmission, stable signal quality, high transmission cost, high transmission power, wide coverage, transmission by antenna feeder, greatly affected by weather conditions, generally used as the first choice for long-distance transmission.
2. The difference between electromagnetic wave modulation methods
Both the signal electromagnetic wave and the local oscillator electromagnetic wave pass through the mixer to obtain the difference frequency, then the intermediate frequency is amplified and detected to obtain the audio signal, and then the audio signal is amplified, and the sound is produced through the earphone or speaker. Superheterodyne means that the local oscillator frequency is one intermediate frequency higher than the signal frequency. On the contrary, if the local oscillator frequency is one intermediate frequency lower than the signal frequency, it is called super internal difference.
3. Difference in working principle
FM is a way of expressing information by the instantaneous frequency change of the carrier, adjusting the frequency of the electromagnetic wave to change with the amplitude of the sound wave; AM achieves the purpose of transmitting information by changing the amplitude of the output signal, and adjusting the amplitude of the electromagnetic wave Changes with the amplitude of the sound wave.
4. The difference in sound quality
The influence of FM interference signal on the amplitude of broadcast signal can be eliminated with a limiter, so the anti-interference ability is very strong, and there is almost no noise; while the anti-interference ability of AM is poor, and the sound quality is poor due to the narrow bandwidth.
Extended information:
Frequency modulation (FM) is one of the most effective synthesis techniques in electronic music synthesis technology. It was first proposed by Dr. John Chowning from Stanford University in the United States.
In the 1960s, Zhuo Ning began to experiment with different types of vibrato at Stanford University. He found that when the frequency of the modulated signal increases and exceeds a certain point, the vibrato effect disappears in the modulated sound and is replaced by a New and more complex sounds.
Amplitude Modulation (AM). Amplitude modulation is also commonly referred to as medium wave, in the range of 530---1600KHz. Amplitude modulation is an electrical signal that uses the level of sound to change the amplitude.
The transmission distance is relatively long, but it is greatly affected by weather factors, so it is suitable for broadcasting by inter-provincial radio stations. Early mobile communication stations in the VHF frequency band mostly used amplitude modulation. Due to channel fading, analog amplitude modulation would produce additional amplitude modulation, causing distortion, and it was also easy to be eavesdropped during transmission, and it has rarely been used at present.
Our other product:
