Classification of wireless microphones
According to different definitions, wireless microphones (wireless conference microphones) can be distinguished into many different types.
1. Distinguish according to the launching frequency: a. FM wireless microphone: Commonly referred to as FM refers to FM 88-108MHz international FM broadcast band. Earlier consumer wireless microphones were received using FM radio. The system was simple and low-cost. However, due to the use effect, it can meet the requirements of professional quality. At present, it can only be a toy for children or students. b. VHF wireless microphone: It is divided into two types: low-frequency and high-band. The former uses the VHF50MHz band. Because the frequency is low, the length of the antenna is too long, and it is the most susceptible to the interference of various electrical clutter, so this type of Products, which have now been replaced by high-frequency bands, have gradually disappeared from the market. The latter uses the VHF200MHz frequency band, because the frequency is higher, the antenna is shorter, and even the hidden antenna can be designed. It is convenient, safe and beautiful, and the clutter interference of the power acceptor is greatly reduced. The circuit design is extremely mature, and the parts are popularized. Because of its low price, it has become a popular model on the market today.
2. Differentiating according to the receiving mode: a. True diversity receiving wireless system: Because the radio wave will produce a "Dead-point" physical phenomenon, the sound of the receiver will be output. The disadvantage of intermittent or unstable, in order to solve this kind of defect, the specialized machine type must use the “Automatic switching diversity receiving” method of the double antenna and double tuner to improve. b. Non-diversity receiving wireless system: As the circuit design of the above-mentioned models is complicated and complicated, the assembly is difficult and the cost is high. Generally, the low-priced models do not adopt the automatic selection design. Therefore, it is impossible to eliminate the shortcomings of the wireless microphone in the use of sound interruption. This type of machine cannot of course meet the basic requirements for professional use.
3, according to the oscillation mode to distinguish: a. Quartz locking (Qualtz locked) models: the quartz oscillator to generate accurate and stable transmission and reception of a fixed frequency, the circuit is simple, low cost, is the standard design of wireless microphones today. This type of microphone and receiver are only used for a single frequency pairing and cannot be changed or adjusted. b. PLL Synthesized models: In order to prevent the wireless microphone from being used when it interferes with other signals in use, or to use multiple microphones at the same time, it is necessary to quickly and easily change the channel at any time. Use PLL circuit design to achieve this type of functionality.
4. Differentiating according to the number of receiver channels: a. Single-channel models: Only one channel of non-automatic selection or automatic selection receiver is installed in the chassis of a receiver. The former has almost no market in Taiwan, but the export market Because the price is the cheapest, it is a big product. The latter is the best model for the use of multiple channels at the same time in professional occasions to avoid signal interference due to its simple use and stable characteristics. b. Dual-channel models: In a receiver's chassis, two channels of non-automatic selection or automatic selection receivers are equipped to make full use of the space of the chassis to reduce costs. The former is the so-called "Asian fighter aircraft" model. Because of its simple design, it has become the main model for mass production of low-cost manufacturers in Taiwan. The latter is complicated because of the complexity of the organization and the circuit, internal interference processing and antenna mix and match. There are only a few models that are specialized in the production of professional models. c. Multi-channel models: In a receiver's chassis, receivers with more than four channels are equipped with modular receiver modules. It is mainly applicable to the occasions where the rack-mounted professional models are used.
With the increasing use of wireless microphones in different occasions, no matter how advanced wireless transmitters and receivers of wireless microphones, will cause signal reception instability due to some special occasions. Here I mainly According to the problems encountered by the proxy wireless microphone in recent years and some solutions, we will discuss with you. An overview of the transmission and reception methods of wireless microphones Let us first briefly understand how the wireless microphones are transmitted and received. Most of the wireless microphones that 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 direct electromagnetic waves, and the VHF band uses direct radiation. In addition to the electromagnetic waves, a part of the refracted and diffracted electromagnetic waves are also used, so the transmission distance can be further extended under the same transmitting power and propagation conditions. With the constant mastery of VHF technology, the range of applications is becoming wider and wider. Therefore, in the space environment of our daily life, there are often many electromagnetic waves in the VHF frequency band. Generally speaking, it works in the VHF band. So if we use a wireless microphone in the VHF band, the chances of getting jammed will be much greater. UHF technology is not yet mastered by many manufacturers, and because the cost of its circuit is more expensive than VHF. Many, so the range of application is not as wide as VHF, and the chances of using UHF wireless microphones will be much less. For this reason, most high-end wireless microphones use UHF technology. The UHF propagation characteristics are more used. It is directly transmitted by radiation, of course, it also has a certain penetrating ability, but if it encounters an object with electromagnetic wave absorption properties (such as metal materials), it will be powerless. We can regard the transmitting antenna of a wireless microphone as a direction. A light emitter that emits light around the cable. The receiving antenna of the wireless microphone can be used as a sensor for the light. When the wireless microphone emits a UHF signal, its transmitting power is generally 10mW (according to the international electromagnetic laws). The transmission distance of the UHF signal is characteristic. Just like our flashlight, as the distance increases, it becomes weaker, so the wireless microphone has a launch distance The problem, and our wireless microphone receiver is like a sensor, as a receiving system, there must be a received sensing value - that is, we often say the receiving sensitivity (SQUELCH), it is like we are professional Similar to the threshold switch of noise gates commonly used in acoustic engineering, only signals with power greater than this threshold can enter the receiver's demodulation circuit. It can be seen that the length of the receiving distance can also be adjusted by adjusting the sensitivity. Sensitivity may also bring some disadvantages. When the sensitivity is too high, it is as if the window in our home is too big. Not only will fresh air come in, but mosquitoes and flies will also come in easily. That is to say sensitivity. When it is too high, it is easy to be disturbed by some weak external noise (for example: mobile phones, high-frequency walkie-talkies), and vice versa, it will affect the receiving effect. When using sensitivity adjustment functions, do not covet excessive receiving distances. , but to look at food to eat, tailored, according to the actual situation. Here everyone on UHF wireless transmission and reception should be Have a certain understanding, here we come to explore solutions for the wireless microphone under some special circumstances stable reception.
1. When there are few people in the performance, there is no problem with the microphone. When the number of people is high, there is a frequency cut. Our friends who often make performances will encounter such problems. During the rehearsal process, the microphones have been used well, but As soon as the audience arrived, the phenomenon of frequency cut occurred at the critical moment of the official performance. In the above we mentioned that the UHF band propagation is generally direct radiation-based, and some of it can also reach the receiver by penetrating obstacles and refractions. , But when we perform, especially when we are playing outdoors, we are surrounded by open spaces. Therefore, refraction cannot exist. In formal performances, the audience will inevitably be many, if the main console is placed in the golden listening of the audience. In the sound position, the receiver's antenna may be blocked by the viewer. Although our UHF signal can penetrate part of the audience's body and reach the receiving antenna, the more objects the signal penetrates, the greater the attenuation will be. When reaching the antenna, its power may not be enough to open the receiver's sensitivity 'gate', which results in a frequency cut.
The solution is as follows:
1.1 If a single set of wireless microphones is used, and this microphone has a sensitivity adjustment function, then we first adjust the sensitivity of the receiver to the maximum. If the frequency cut-off phenomenon still occurs, you can place the microphone higher than the audience (the most It's better to place it on the stage) or to extend the antenna of the microphone outside, but we need an auxiliary device, the antenna amplifier, because it will bring some loss of gain when extending the antenna cable. Adding an antenna amplifier can compensate for the loss of gain caused by the coaxial cable.
1.2 If multiple sets of wireless microphones are used, we would not be able to place as many wireless microphones on the stage at this time, and if we want to pull a lot of antennas on the top of the console, it would not seem like a real thing. We still have a solution to this type of problem. We can add another kind of device, a wireless microphone antenna splitter. This device can use an internal matching circuit to allow several sets of microphones to share one antenna, and then cooperate with the antenna amplifier. At this time, look for two higher microphone stands to support the antenna amplifier, so that we can solve the problem of stable reception when multiple sets of microphones are used at the same time.
2. When performing on a relatively large occasion, due to the relatively large space for microphone users to move, the launch distance of wireless microphones cannot meet the needs. When we perform a large-scale concert in a stadium, we often build a big stage, and Building a few storey ceilings, all of which are detrimental to the use of wireless microphones. As we all know, wireless microphones have a standard launch power of 10mW. The distance traveled is very limited due to propagation in the air and the blocking and absorption of some substances. And, the receiver's sensitivity setting will also have a certain impact on the receiving distance. The general wireless microphone launch distance is: 50 to 120 meters distance, if the use of the environment has a strong electromagnetic interference or electromagnetic Shielding, the launch distance may not exceed 50 meters. For the above reasons, the wireless microphone will still be tested in large-scale performances, but if it is used in conjunction with an antenna splitter and antenna amplifier, it can be to a large extent. In order to avoid the problem of disconnection, if we use four sets of wireless microphones, we only need one antenna splitter and two antennas to amplify it. , to form a combination of Figure 7 style. It is only that we have to use the coaxial cable to pull the antenna amplifier as close as possible to the side of the stage, if it can be fixed on the stage of the light frame that would be great. This kind of condescending antenna installation , It can be ensured that the transmitted signal is not blocked in most cases, thus ensuring a stable receiving effect. With this method we can also make some trade-offs, if we want to ensure stronger reception stability, then two The distance between the antenna amplifiers is kept between 50M and 100M as much as possible, because we can use the automatic selection function of the microphone to select the strongest signal among the two antenna amplifiers as the received signal; the other case is If we want to achieve a long enough distance, we can adjust the distance between the two antenna amplifiers to between 100M~180M. At this time, we just use the unilateral antenna of the microphone to receive, so the receiving diameter of the microphone (in two The midpoint of the antenna amplifiers can be about 400 meters in theory, but this is the result of the loss of stability. Distance
3. In addition, there is another situation that we may encounter when we do engineering: When we work on some confidentiality units, we suddenly find that the launch distance of wireless microphones is only ten meters. This is because Some units installed electromagnetic shielding on the wall of a building to prevent electromagnetic leakage. Therefore, the signals of our wireless microphones would not penetrate the walls and thus affected the launch distance. The solution to this problem was very simple. We just use the coaxial cable to pass through the wall, connect the antenna amplifier to the end that needs to receive the signal, and connect the wireless microphone to the other end. This will not leak the electromagnetic wave signal of the user, but also achieve the stable reception of the microphone. the goal of.
According to different definitions, wireless microphones (wireless conference microphones) can be distinguished into many different types.
1. Distinguish according to the launching frequency: a. FM wireless microphone: Commonly referred to as FM refers to FM 88-108MHz international FM broadcast band. Earlier consumer wireless microphones were received using FM radio. The system was simple and low-cost. However, due to the use effect, it can meet the requirements of professional quality. At present, it can only be a toy for children or students. b. VHF wireless microphone: It is divided into two types: low-frequency and high-band. The former uses the VHF50MHz band. Because the frequency is low, the length of the antenna is too long, and it is the most susceptible to the interference of various electrical clutter, so this type of Products, which have now been replaced by high-frequency bands, have gradually disappeared from the market. The latter uses the VHF200MHz frequency band, because the frequency is higher, the antenna is shorter, and even the hidden antenna can be designed. It is convenient, safe and beautiful, and the clutter interference of the power acceptor is greatly reduced. The circuit design is extremely mature, and the parts are popularized. Because of its low price, it has become a popular model on the market today.
2. Differentiating according to the receiving mode: a. True diversity receiving wireless system: Because the radio wave will produce a "Dead-point" physical phenomenon, the sound of the receiver will be output. The disadvantage of intermittent or unstable, in order to solve this kind of defect, the specialized machine type must use the “Automatic switching diversity receiving” method of the double antenna and double tuner to improve. b. Non-diversity receiving wireless system: As the circuit design of the above-mentioned models is complicated and complicated, the assembly is difficult and the cost is high. Generally, the low-priced models do not adopt the automatic selection design. Therefore, it is impossible to eliminate the shortcomings of the wireless microphone in the use of sound interruption. This type of machine cannot of course meet the basic requirements for professional use.
3, according to the oscillation mode to distinguish: a. Quartz locking (Qualtz locked) models: the quartz oscillator to generate accurate and stable transmission and reception of a fixed frequency, the circuit is simple, low cost, is the standard design of wireless microphones today. This type of microphone and receiver are only used for a single frequency pairing and cannot be changed or adjusted. b. PLL Synthesized models: In order to prevent the wireless microphone from being used when it interferes with other signals in use, or to use multiple microphones at the same time, it is necessary to quickly and easily change the channel at any time. Use PLL circuit design to achieve this type of functionality.
4. Differentiating according to the number of receiver channels: a. Single-channel models: Only one channel of non-automatic selection or automatic selection receiver is installed in the chassis of a receiver. The former has almost no market in Taiwan, but the export market Because the price is the cheapest, it is a big product. The latter is the best model for the use of multiple channels at the same time in professional occasions to avoid signal interference due to its simple use and stable characteristics. b. Dual-channel models: In a receiver's chassis, two channels of non-automatic selection or automatic selection receivers are equipped to make full use of the space of the chassis to reduce costs. The former is the so-called "Asian fighter aircraft" model. Because of its simple design, it has become the main model for mass production of low-cost manufacturers in Taiwan. The latter is complicated because of the complexity of the organization and the circuit, internal interference processing and antenna mix and match. There are only a few models that are specialized in the production of professional models. c. Multi-channel models: In a receiver's chassis, receivers with more than four channels are equipped with modular receiver modules. It is mainly applicable to the occasions where the rack-mounted professional models are used.
With the increasing use of wireless microphones in different occasions, no matter how advanced wireless transmitters and receivers of wireless microphones, will cause signal reception instability due to some special occasions. Here I mainly According to the problems encountered by the proxy wireless microphone in recent years and some solutions, we will discuss with you. An overview of the transmission and reception methods of wireless microphones Let us first briefly understand how the wireless microphones are transmitted and received. Most of the wireless microphones that 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 direct electromagnetic waves, and the VHF band uses direct radiation. In addition to the electromagnetic waves, a part of the refracted and diffracted electromagnetic waves are also used, so the transmission distance can be further extended under the same transmitting power and propagation conditions. With the constant mastery of VHF technology, the range of applications is becoming wider and wider. Therefore, in the space environment of our daily life, there are often many electromagnetic waves in the VHF frequency band. Generally speaking, it works in the VHF band. So if we use a wireless microphone in the VHF band, the chances of getting jammed will be much greater. UHF technology is not yet mastered by many manufacturers, and because the cost of its circuit is more expensive than VHF. Many, so the range of application is not as wide as VHF, and the chances of using UHF wireless microphones will be much less. For this reason, most high-end wireless microphones use UHF technology. The UHF propagation characteristics are more used. It is directly transmitted by radiation, of course, it also has a certain penetrating ability, but if it encounters an object with electromagnetic wave absorption properties (such as metal materials), it will be powerless. We can regard the transmitting antenna of a wireless microphone as a direction. A light emitter that emits light around the cable. The receiving antenna of the wireless microphone can be used as a sensor for the light. When the wireless microphone emits a UHF signal, its transmitting power is generally 10mW (according to the international electromagnetic laws). The transmission distance of the UHF signal is characteristic. Just like our flashlight, as the distance increases, it becomes weaker, so the wireless microphone has a launch distance The problem, and our wireless microphone receiver is like a sensor, as a receiving system, there must be a received sensing value - that is, we often say the receiving sensitivity (SQUELCH), it is like we are professional Similar to the threshold switch of noise gates commonly used in acoustic engineering, only signals with power greater than this threshold can enter the receiver's demodulation circuit. It can be seen that the length of the receiving distance can also be adjusted by adjusting the sensitivity. Sensitivity may also bring some disadvantages. When the sensitivity is too high, it is as if the window in our home is too big. Not only will fresh air come in, but mosquitoes and flies will also come in easily. That is to say sensitivity. When it is too high, it is easy to be disturbed by some weak external noise (for example: mobile phones, high-frequency walkie-talkies), and vice versa, it will affect the receiving effect. When using sensitivity adjustment functions, do not covet excessive receiving distances. , but to look at food to eat, tailored, according to the actual situation. Here everyone on UHF wireless transmission and reception should be Have a certain understanding, here we come to explore solutions for the wireless microphone under some special circumstances stable reception.
1. When there are few people in the performance, there is no problem with the microphone. When the number of people is high, there is a frequency cut. Our friends who often make performances will encounter such problems. During the rehearsal process, the microphones have been used well, but As soon as the audience arrived, the phenomenon of frequency cut occurred at the critical moment of the official performance. In the above we mentioned that the UHF band propagation is generally direct radiation-based, and some of it can also reach the receiver by penetrating obstacles and refractions. , But when we perform, especially when we are playing outdoors, we are surrounded by open spaces. Therefore, refraction cannot exist. In formal performances, the audience will inevitably be many, if the main console is placed in the golden listening of the audience. In the sound position, the receiver's antenna may be blocked by the viewer. Although our UHF signal can penetrate part of the audience's body and reach the receiving antenna, the more objects the signal penetrates, the greater the attenuation will be. When reaching the antenna, its power may not be enough to open the receiver's sensitivity 'gate', which results in a frequency cut.
The solution is as follows:
1.1 If a single set of wireless microphones is used, and this microphone has a sensitivity adjustment function, then we first adjust the sensitivity of the receiver to the maximum. If the frequency cut-off phenomenon still occurs, you can place the microphone higher than the audience (the most It's better to place it on the stage) or to extend the antenna of the microphone outside, but we need an auxiliary device, the antenna amplifier, because it will bring some loss of gain when extending the antenna cable. Adding an antenna amplifier can compensate for the loss of gain caused by the coaxial cable.
1.2 If multiple sets of wireless microphones are used, we would not be able to place as many wireless microphones on the stage at this time, and if we want to pull a lot of antennas on the top of the console, it would not seem like a real thing. We still have a solution to this type of problem. We can add another kind of device, a wireless microphone antenna splitter. This device can use an internal matching circuit to allow several sets of microphones to share one antenna, and then cooperate with the antenna amplifier. At this time, look for two higher microphone stands to support the antenna amplifier, so that we can solve the problem of stable reception when multiple sets of microphones are used at the same time.
2. When performing on a relatively large occasion, due to the relatively large space for microphone users to move, the launch distance of wireless microphones cannot meet the needs. When we perform a large-scale concert in a stadium, we often build a big stage, and Building a few storey ceilings, all of which are detrimental to the use of wireless microphones. As we all know, wireless microphones have a standard launch power of 10mW. The distance traveled is very limited due to propagation in the air and the blocking and absorption of some substances. And, the receiver's sensitivity setting will also have a certain impact on the receiving distance. The general wireless microphone launch distance is: 50 to 120 meters distance, if the use of the environment has a strong electromagnetic interference or electromagnetic Shielding, the launch distance may not exceed 50 meters. For the above reasons, the wireless microphone will still be tested in large-scale performances, but if it is used in conjunction with an antenna splitter and antenna amplifier, it can be to a large extent. In order to avoid the problem of disconnection, if we use four sets of wireless microphones, we only need one antenna splitter and two antennas to amplify it. , to form a combination of Figure 7 style. It is only that we have to use the coaxial cable to pull the antenna amplifier as close as possible to the side of the stage, if it can be fixed on the stage of the light frame that would be great. This kind of condescending antenna installation , It can be ensured that the transmitted signal is not blocked in most cases, thus ensuring a stable receiving effect. With this method we can also make some trade-offs, if we want to ensure stronger reception stability, then two The distance between the antenna amplifiers is kept between 50M and 100M as much as possible, because we can use the automatic selection function of the microphone to select the strongest signal among the two antenna amplifiers as the received signal; the other case is If we want to achieve a long enough distance, we can adjust the distance between the two antenna amplifiers to between 100M~180M. At this time, we just use the unilateral antenna of the microphone to receive, so the receiving diameter of the microphone (in two The midpoint of the antenna amplifiers can be about 400 meters in theory, but this is the result of the loss of stability. Distance
3. In addition, there is another situation that we may encounter when we do engineering: When we work on some confidentiality units, we suddenly find that the launch distance of wireless microphones is only ten meters. This is because Some units installed electromagnetic shielding on the wall of a building to prevent electromagnetic leakage. Therefore, the signals of our wireless microphones would not penetrate the walls and thus affected the launch distance. The solution to this problem was very simple. We just use the coaxial cable to pass through the wall, connect the antenna amplifier to the end that needs to receive the signal, and connect the wireless microphone to the other end. This will not leak the electromagnetic wave signal of the user, but also achieve the stable reception of the microphone. the goal of.
