Wireless microphones have gone through three phases, from the initial simple radio transmitter and wireless FM receiver to the current proprietary PLL (frequency phase-locked loop) technology.
1. Simple FM transmission and reception
At that time, in order to get rid of the shackles of the microphone cable, people thought of the transmission and reception principle similar to FM radio, through the principle of the microphone's transduction and audio → modulation → amplification → transmission process, and then through the FM radio or dedicated receiver (special frequency ) Receive and play. It can be imagined that its sound quality, stability, anti-interference ability, etc. cannot meet the needs of actual use.
2. Quartz oscillation FM transmission and reception
Due to the RC or LC oscillation generated by the electronic circuit, the stability of the oscillation frequency is greatly affected by the environment, and the frequency thereof is not likely to be very high. Generally, it can only be below two or three hundred megahertz. In such a frequency band, it is highly susceptible to interference from other signals and a transmitting and receiving circuit using a quartz oscillator is present. As we all know, the oscillation frequency of quartz crystal is very stable. The wireless microphone transmitter and receiver composed of it is much more stable when working. At the same time, its working frequency can be in V segment (30MHZ-250MHZ), U segment (200-1000MHZ), the external interference signal is not serious, which brings good results to the use of wireless microphones.
3. Wireless microphone with PLL reception
The PLL is an abbreviation of the frequency phase lock loop. In the transmission and reception of the wireless microphone, the frequency synthesis method can be used to receive the signal satisfactorily in one frequency band. In this frequency band, the working channel can also be switched arbitrarily. In theory, in a 24 MHz band, if 1 MHz is used as the channel resolution, 25 channels can be switched; if 125 KHZ, 193 channels can be switched, as to the number of channels and the bandwidth and channel resolution of the receiver. In actual use, it is necessary to take into account various factors, but it is certain that the wireless microphone with PLL technology has adjustable receiving channels and more than one, which brings great flexibility in use. The transmitter and receiver can also be combined at will, and the working channel can be switched at any time within a bandwidth range to avoid interference.
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