The Reason and Countermeasure of Frequent Interference of Wi

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Each wireless transmitter device occupies a frequency bandwidth at work, just as each car occupies a carriageway, where the frequency is like a highway, the bandwidth is like there are numerous lanes on the road, and The microphone receiver is like a car on the carriageway. When the wireless device works, if other devices use your band. It's like taking your lane. So people are often waiting for the car is not their own car.



Frequency hopping technology

This and you are genuine or imitation goods, manufacturers or small factories of the wireless microphone does not have any relationship, all the world's microphone manufacturers have no way to completely solve the microphone receiver by other interference with the same frequency signal. Of course, excellent manufacturers will use technical means to minimize this possibility, the transmitter to minimize spurious emissions such as: parasitic, intermodulation, harmonics, etc., while the receiver is SQ (Squelch, squelch threshold) or narrow Frequency operation, frequency hopping technology and so on. In order to solve the impact of interference on its system, and the system within the wireless microphone to get more use of the number.

But the current really can be a relatively effective solution or the use of frequency hopping technology, this development for military communications technology is the first after World War II for the confidentiality of communication and a spread spectrum technology. Now has long been widely used in civilian communications, such as CDMA communications.

There are already many manufacturers are trying to use this frequency hopping technology in the wireless microphone system. This is now a more effective to avoid interference with a technology. But because of the high price is difficult to popular.

Most of the interference is inadvertently formed, usually other equipment in the normal operation of the interference generated by the interference source will not interfere with the transmitter, the interference is the wireless receiver, in this to form a basic concept.





What are the sources of wireless interference?

In the following, we make a brief description of the wireless microphones that are often disturbed, so that you know where to start from the actual situation. It is important to note that there are many kinds of wireless interference sources in mainland China: 1. Interference with the same frequency; 2. Electromagnetic interference; 3. Intermodulation interference.

Because wireless interference involves a lot of knowledge, so here we use some non-professional terms to tell the whole process, the purpose is to allow users to easily grasp the use of equipment, rather than academic discussion, so please do not have too much radio frequency radio friends in the text used Terminology and explanation.

Interference with the same frequency

As the name suggests, the frequency you use has other wireless signals, thus hampering the propagation of our wireless microphones. This interference enters the machine through the antenna of the receiver, so that we can not receive the wireless microphone.

1, walkie-talkie, especially when some high-power transmitter work, the spurious emission is particularly large. Perhaps the frequency of its work is not the frequency we use, but due to parasitic, harmonic and other out-of-band emissions, it should be possible to produce some of the incident launch into our frequency, causing interference to our wireless microphone.

2, other wireless transmitter equipment, equipment, microphones, home appliances, base station operating frequency and we may use the same frequency, so that the wireless microphone signal transmission is disturbed.

Electromagnetic interference

Some high-power instruments and equipment in the work will produce high-power harmonic emission or electromagnetic field, especially in the case of very close. These radio frequency energy will be concentrated in some circuits, resulting in a part of the wireless microphone receiver circuit can not work.

Such as switching power supplies, induction cookers, microwave ovens, wireless charging, which belong to the energy field of energy accumulation. Modern warfare is also often used to destroy the principle of energy, such as the latest microwave gun, specifically used to destroy the enemy's electronic equipment, as well as frequent use of high-power directional antenna interference with each other's communications equipment, are the principle.

These devices work on the surrounding circuit to generate electromagnetic energy accumulation, and therefore may be disturbed by the signal transmission more. Such as audio signals, video signals, wireless signals, are likely to be disturbed, and even the microcontroller can be disturbed. This is why the cell phone signal and the aeronautical communication signal are not in a band, while the plane is still not allowed to use the telephone and some signal transmission equipment reasons. Think about the gas station is not allowed to use the phone may be more direct.

Intermodulation interference

Intermodulation interference is what, do not do too much description, intermodulation interference for the receiver is actually a type of interference with the same frequency. Simply put, you use the wireless microphone more, resulting in intermodulation interference is more, this interference is generated by our wireless microphone itself, from our microphone launch.

Third-order intermodulation is the greatest damage to us, if you use the two microphones 800MHZ and 801MHZ, then the 799 and 802MHZ frequency will produce third-order intermodulation signal, this signal may affect the use of other microphones, So the more the microphone, the more interference. However, it should be noted that the intermodulation interference signal strength is lower than the microphone signal strength is being used.






How to avoid?

Usually we use the wireless microphone device, the first equipment to install the location of planning, planning the advantage is to avoid electromagnetic interference, so the installation should comply with the following principles:

1, to avoid and may have a strong electromagnetic field equipment installed together, such as microwave ovens, induction cooker, motor, generators, etc .;

2, as far as possible away from the switching power supply circuit, RF circuit, high-frequency pulse circuit, such as: LED large screen, high-power radio, walkie-talkie, high voltage generator, negative ion generator. Focus on the LED large screen, because there are a large number of internal switching power supply, easily affect the receiver work;

3, do not with other equipment, especially the switching power supply equipment, launch equipment installed in the same cabinet, such as DVD players, VOD machines, equipment, power transformers, switching power supply;

4, the installation of wireless microphone to follow the principle of independence, as far as possible away from other equipment, small electromagnetic interference source is basically separated by 50 cm or more relatively safe, large interference sources such as LED screen, then generally more than 5 meters relative security.

After the installation of the equipment, we have to use the frequency of wireless microphone planning, the so-called planning is to arrange the frequency we want to use, and other unrelated signals to avoid using the same frequency, so as not to receive interference signals. The easiest way is to step through all the receivers we want to use and the wireless microphone, and then tune. Proceed as follows:

The first step: open all the microphone with the receiver, and match well to ensure that each microphone and receiver work properly connected.

Step 2: Turn off the No. 1 microphone according to the number, observe the RF signal of the receiver. If the RF signal is lit or has a change in intensity, it indicates that the same frequency of the wireless signal enters the receiver. We do not have to interfere with the interference signal from the outside world or intermodulation interference between the microphone. We fine-tune the accept frequency until the RF signal is not.

Step 3: Save the newly selected frequency and match the microphone to connect properly. Do not turn off any microphone, all in the power on.

Step 4: Turn off the No. 2 wireless microphone Repeat Step 2 Step 3 until all the microphones have finished debugging.

Step 5: follow the above steps to check all the new microphone, if there is still interference signal, the corresponding microphone from the new debugging time. Generally basically reach the use of requirements.

After the above system debugging, the wireless microphone has basically avoided all the antenna from the received wireless interference signal. Theoretically already can be used normally. But we still have to pay attention to a special situation, that is, sudden interference.

(Sudden interference means that we are in the process of debugging, this interference does not exist, but when after a period of time, a nearby or peripheral wireless equipment to open the work, the frequency used is exactly what we use the frequency, This interference is caused by our use of the microphone, which we can not foresee, so we can not be excluded from the pre-work, such as automatic remote monitoring, monitoring equipment, timing wireless transmission equipment, etc. These devices may not Timing or timing of the launch, and when this interference is encountered, it is generally necessary to immediately turn off the microphone receiver and enable the standby microphone.

For some of the above debugging methods, the vast majority can avoid the impact of interference, while many manufacturers also use the latest technology developed a key to avoid interference with the wireless microphone system, through a button action, automatically complete all the debugging work.






Analysis of Common Problems in Wireless System

Above we talked about some of the common interference and avoidance of the microphone. Then let's talk about some related questions. These problems are actually used in the wireless microphone is common, but because the domestic performance equipment rental industry for wireless audio equipment RF planning work is not particularly important, and become a weak part of the technology. This hope that the domestic counterparts as soon as possible international team, the team equipped with radio frequency engineers.

1, sometimes used when the receiver outputs a creaky voice, sometimes not.

This interference is frequency interference. The energy is not the same, but because you are using the same frequency. So when your microphone signal is weak, the interference signal will be able to form an impact, the characteristics of the wireless signal is strong to suppress the weak, so this time is often narrowly meet the brave win. Who has the power, who has the advantage.

2, why the microphone to do the launch power so small, can not do big?

Wireless Microphones are conventional for 10-50, the most common is about 30 mW, the SHURE-PGX series is a lot of 10 mW, the UR series of 10-50 mW can be tuned; Sennheiser XSW series 10 mW; Sennheiser EW Series 30 mW; AMSAUDIO TC Series 30 mW.

The transmit power varies according to the requirements of each country, the same model, in different countries are set to different transmission power, and high-power launch is not conducive to battery life, resulting in shorter use of time.

3, why the receiver can receive some broadcast signal?

Wireless microphone receiver and the general radio walkie-talkie reception is no essential difference, most of the use of analog carrier frequency transmission, if the broadcast signal into the receiver to accept the frequency, theoretically can be received normally. For example, many of the current broadcast channel is just our frequent use of the frequency of the microphone, and does not rule out some of the broadcast station produced by the intermodulation signal transmission or harmonic emission.

4, the rain will make the use of wireless microphone closer?

Will rain, rain due to the formation of the rain on the wireless signal attenuation, so the use of wireless microphone will obviously feel closer.

5, wireless microphone to choose what the frequency of good?

Now the mainstream of the wireless microphone are used U work, 500MHz-850MHz or so. Some large brands have produced G-segment (1000MHz-2400MHz) microphone, the majority of domestic manufacturers to produce 700MHz-850MHZ about the microphone. V-segment machines are the last generation of products, and now rarely used as a show.

Choose what frequency of the microphone is good, first talk about the frequency of the microphone. RF work has a characteristic, the higher the frequency, the more the characteristics of light. The lower the trend of sound. High-frequency directness is good, linear transmission, the frequency bandwidth occupied less. Low, then the diffraction is good, easy to get around, which also shows why long-distance communication with shortwave.

Close with the use of high-frequency, long-range use of low frequency. So when we use a higher frequency of the microphone, it is easy to be affected by any little bit of environmental changes, even if you waved, are likely to cause a brief loss of the signal.

So the use of higher frequency transmission, then the distance is a big problem. We can see Senhai's latest 2.4GHz products, he recommended you to use the conference church lecture class, did not recommend you to perform.

While the lower frequency of work, more vulnerable to interference, because the current low-frequency wireless environment is very complex, very much interference source, so the low frequency band is more dangerous.

But the above points are not as you choose the basis of the frequency of the microphone, because the above reasons, although the real existence, but the actual use, in the current 500MHz-850MHz band. High and low impact on the user is not particularly obvious. Frequency selection is mainly to see what their current microphone is what frequency band, the current city where the open radio which band. For the above bands. Choose to avoid repetitive frequencies as much as possible.

6, why the wireless microphone frequency, how to distinguish between the phenomenon?

Breakdown is the wireless microphone work often encountered a problem, simply is the wireless microphone and receiver lost connection after the phenomenon known as the frequency off.

Breaking frequency phenomenon is a comprehensive appearance, wireless microphone and receiver of any problems may cause breaking frequency, it can not say that the frequency must be caused by interference.

Interference frequency, the receiver received interference, resulting in the microphone can not receive the normal signal, so the frequency off, generally by turning off the wireless microphone to see the receiver's RF signal to determine, if there is interference signal light.

Distance off frequency, wireless microphone beyond the receiver to receive the signal range, resulting in frequency off. This off-frequency can be ruled out by controlling the use of wireless microphones.

Installation error frequency, this frequency is often used in actual use, the use of distance is significantly smaller than the conventional use of distance. Commonly used in the installation of the wrong cabinet, or the equipment installed in the wrong venue, pay attention to the receiver antenna should be completely exposed, and the two antennas into a V-shaped angle. The entire receiver antenna and the crowd, and the microphone as much as possible to avoid obstacles.

7, rehearsal time is good, the official performance of the microphone when there is interference or frequency off.

First of all to distinguish between what kind of fault, the general rehearsal, the wireless microphone are tried to start, and then the official performance of the wireless microphone for a while will find a variety of problems. And these problems in the field because it can not be second debugging, often let people rush to know what to do.

8, more than a wireless microphone creaky noise, and even some microphone no sound, and sometimes even clear in the end which microphone microphone.

This situation is generally caused by the intermodulation interference of the microphone, because there is no tone, the official performance, with the microphone sequence disruption, and the number of increase or change, the microphone intermodulation interference problems, resulting in a part of the microphone can not Work, this situation is difficult to exclude temporarily. Usually close some of the microphone, do not use.

So the performance should be on the microphone before the tune. The closer the receiver is to the stage, especially when the stage is used or the antenna amplifier is used.

(The receiver is nearly the same distance from the stage, but when the system is not in tune, the intermodulation interference signal is closer to the receiver because it is close to the receiver)

9, wireless microphone only a noise or no signal.

This situation may be the microphone by the same frequency of sudden interference, generally only need to turn off the microphone, and then adjust the receiver frequency. Observe the signal, avoid interference, re-match the microphone on it, but this set of re-matching microphone recommended as a backup microphone, because most likely and the first tone of the other microphone intermodulation interference.

10, wireless microphone