Recently, from the perspective of product stability, especially our customers' feedback on the influence of sunlight on product signal transmission, we have prompted us to upgrade the signal transmission of the product T3508.
From the beginning of the AM transmission (AM is usually referred to as the medium wave, the range is 530---1600KHz, the transmission distance is longer, but it is greatly affected by the weather), and it is changed to FM transmission
The difference between FM and AM
(1) FM has stronger anti-interference ability than amplitude modulation:
The influence of various external interference, processing industry and antenna interference, etc. on the modulated wave is mainly manifested in the generation of parasitic amplitude modulation and the formation of noise. The frequency modulation system can use the method of limiting amplitude to eliminate the parasitic amplitude modulation caused by interference. In the AM system, the amplitude of the amplitude-modulated signal is variable, so amplitude limiting cannot be used, and it is difficult to eliminate external interference.
In addition, the greater the signal-to-noise ratio of the signal, the stronger the anti-interference ability. The signal-to-noise ratio of the signal obtained after demodulation is related to the modulation coefficient. The larger the modulation coefficient, the larger the signal-to-noise ratio. Since the frequency modulation coefficient is much larger than the amplitude modulation coefficient, the signal-to-noise ratio of the FM wave is high, and the interference noise in FM broadcasting is small.
(2) FM wave ratio and amplitude modulation wave frequency bandwidth:
The frequency bandwidth is related to the modulation factor, that is, the modulation factor is large and the frequency bandwidth is wide. In FM, the frequency modulation coefficient is usually greater than 1, and the amplitude modulation coefficient is less than 1. Therefore, the frequency bandwidth of the frequency modulation wave is much larger than that of the amplitude modulation wave.
(3) The power utilization rate of the frequency modulation system is greater than that of the amplitude modulation system:
In the total transmission power, the side frequency power is the effective power of the transmitted modulation signal, and the side frequency power is related to the modulation coefficient, the modulation coefficient is large, and the side frequency power is large. Since the frequency modulation coefficient mf is greater than the amplitude modulation coefficient ma, the power utilization rate of the frequency modulation system is higher than that of the amplitude modulation system.