An overview of the transmitting and receiving methods of wireless microphones. First, let us have a general understanding of the transmitting and receiving methods of wireless microphones. Most of the wireless microphones we often use are working in the VHF band or UHF band. The radio signals in the VHF and UHF bands are collectively referred to as radio frequency signals (RF). The UHF band uses more directly radiated electromagnetic waves, and the VHF band uses direct radiation. In addition to the electromagnetic waves, a part of the electromagnetic waves that are refracted and diffracted are also used, so under the same transmission power and propagation conditions, the transmission distance can be longer.
With the continuous mastery of VHF technology, the scope of application is getting wider and wider. Therefore, the space environment of our daily life is often filled with electromagnetic waves in the VHF frequency band. Commonly used walkie-talkies generally work in the VHF frequency band, so if When we use wireless microphones in the VHF frequency band, the chances of interference will be great, and UHF technology is not yet mastered by many manufacturers.
Because the cost of its circuit is much more expensive than VHF, the range of applications is not as wide as VHF, and the chance of interference with UHF wireless microphones will be much smaller. For this reason, most high-end wireless microphones will use UHF technology. , UHF's propagation characteristics are more direct radiation transmission, of course, it also has a certain penetration ability, but if it encounters objects with electromagnetic wave absorption characteristics (such as metal substances), it will be powerless.
We can regard the transmitting antenna of the wireless microphone as a luminous body that emits light to the surroundings, while the receiving antenna of the wireless microphone can be used as a sensor of light. When the wireless microphone emits UHF signals, its transmitting power is generally
10mW (according to international electromagnetic regulations), the characteristics of the transmission distance of UHF signals are just like our flashlights, which become weaker and weaker as the distance increases. Therefore, wireless microphones have a transmission distance problem, and our wireless microphones receive The machine is like a sensor. As a receiving system, it must have a received induction value which is what we often call the receiving sensitivity (SQUELCH). It is like the threshold switch of the noise gate we commonly use in professional audio engineering. Only signals with power greater than this threshold can enter the demodulation circuit of the receiver. It can be seen that the length of the receiving distance can also be adjusted by adjusting the sensitivity. However, adjusting the sensitivity may also bring some disadvantages, when the sensitivity is too high time,
Just like when the windows in our house are open too big, not only fresh air comes in, but mosquitoes and flies often come in easily, which means that when the sensitivity is too high, it is easy to be affected by some weak noise outside. Interference (for example: mobile phone high-frequency walkie-talkie), otherwise it will affect the receiving effect. When we use the sensitivity adjustment function, do not covet too large receiving distance, but to look at the food and eat, and tailor the clothes according to the actual situation. Solutions for stable reception
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