The simultaneous use of dozens of wireless microphones is no longer a novelty in today's performance market due to live sound reinforcement activities. However, the increasingly complex live broadcast environment brings many problems to the simultaneous use of wireless microphones.
For whatever reason, these problems tend to interfere with the radio signal in the field, making the sound produced by the wireless system when transmitting the audio signal intermittent, many of us do not want to see the result, such as receiver output noise and microphone string frequency. As professional and technical personnel, we always have to have corresponding solutions to deal with these situations.
Interference source analysis
To come up with a solution, we must first identify these general sources of interference:
1. High-power radio station;
2. Civil radio towers;
3. Intercom and wireless intercom system;
4. Other wireless systems and high-power induction appliances with similar operating frequency and debugging mode to wireless microphones;
5. On-site internal interference of wireless sound reinforcement system.
As mentioned above, several of the categories mentioned above are generally easy to understand. Whether it is a broadcasting station set up by the state or a communication equipment base station set up by enterprises or individuals, or a wireless communication system frequently used by our local, as well as a large screen containing a high-power circuit, all contain high-power circuits, and the wireless communication system frequently used in our existing wireless system, as well as a large screen such as a large screen. High-power wireless signals emitted that conflict with the frequency range of our existing wireless systems are extremely vulnerable.
Due to the scope stipulated by national laws, the wireless transmission power of professional audio signals is limited to tens of milliwatts, and the power of these interference sources can reach several watts or even tens of watts. Because the wireless audio signal receiving system has a large power difference, it can not resist strong interference sources.
What can be done on the spot is to arrange the antenna reasonably, set the appropriate gain, and try to avoid receiving these interference signals. In addition, from the perspective of frequency planning, it is necessary to make the working frequency of the wireless system as far away from the working area of these interference sources as possible.
However, the last one is very important, because the wireless system internal frequency and other aspects of the improper planning and disposal of signal interference, often ignored, which is mainly reflected in:
1. Wireless system frequency planning is not scientific enough;
2. Design defects in the number and placement of transmitting and receiving antennas in the system;
3. The RF signal transmission line that does not meet the requirements is used;
4. The RF signal transmission distance is too long, which will produce unacceptable RF noise.
The topic of this paper is how to avoid interference signals caused by intermodulation distortion between our own wireless devices, which threatens the stability of the wireless system. Next, I'll briefly describe some common setup scenarios and point out the wrong behaviors that can cause this problem.
The first thing to point out is that we need to pay attention to this problem only when the noise in the radio environment is high and multiple radio transmitting devices are in close proximity. If you're playing in a relatively regular indie band and you're only using a wireless microphone for the lead singer, you don't have to consider any of these issues.
However, it is very common in some major music festivals, live radio evenings or theatrical plays or vaudeville performances. The handheld or Fanny pack launcher is combined and turned on.
Although these wireless microphones are managed by a person, they are sent to the people who need them at a specific time. But this situation is still inevitable, in many cases, there are several wireless transmitters closely linked together, and are all open.