Every wireless transmitting device (including wireless microphones, bodypack transmitters, conference transmitters, etc.) occupies a specific frequency bandwidth during operation, similar to how each vehicle occupies a lane on a highway.
In this analogy, the frequency is equivalent to the “road,” while the bandwidth represents the total “lanes.” The receiver of a wireless microphone is like a “person” waiting for a signal on a particular lane.
When another device uses the same frequency, it is akin to “blocking the lane,” preventing the receiver from properly receiving its intended signal; this phenomenon is referred to as interference.
Typically, wireless microphone interference is not directly related to the brand. In fact, no manufacturer worldwide can completely eliminate the possibility of co-channel interference.
However, high-quality manufacturers (such as AMSaudio) optimize their technology to minimize interference as much as possible.
For instance, transmitters reduce interference by lowering spurious emissions (parasitic, intermodulation, harmonics, etc.), while receivers employ Squelch thresholds, Narrowband Operation, and Frequency Hopping Technology to reduce the impact of interference, thereby increasing the usable number of wireless microphones and stabilizing signal performance.
Currently, there are many technical approaches to handle interference, but none can address all types of interference completely.
For example, using wideband can resolve interference in a specific frequency range; frequency hopping can automatically switch when a frequency is occupied; and digital modulation can partially avoid intermodulation interference.
These methods optimize the performance of wireless microphone systems but cannot entirely eliminate interference issues.
It is important to note that interference mainly affects the receiver rather than the microphone transmitter. Interference is often unintentional and usually originates from the normal operation of other devices. Therefore, understanding the core concept that “interference affects reception, not transmission” is essential.
Types of Interference
Common types of interference in wireless microphone systems are as follows:
1. Co-channel Interference
Co-channel interference occurs when your wireless microphone operates on the same frequency as another device. Interference signals enter the system through the receiver’s antenna, causing signal loss or noise.
Interference from two-way radios: Some high-power two-way radios generate spurious emissions during operation. Although their operating frequencies may differ, harmonics or parasitic signals may fall into the microphone’s operating band, causing interference.
Interference from other wireless devices: If base stations, microphones, or other wireless systems overlap in frequency, they can also affect signal propagation.
2.Electromagnetic Interference (EMI)
High-power devices such as switching power supplies, induction cookers, and microwave ovens generate strong electromagnetic fields during operation. When close to the receiver, they can affect internal circuits, causing signal distortion or interruption.
In wireless system layouts, these devices should be kept away from receiver antennas whenever possible.
3.Intermodulation Interference
Intermodulation interference is one of the most common types when multiple wireless microphones are used simultaneously.
For example, if two microphones operate at 800 MHz and 801 MHz, third-order intermodulation signals may appear at 799 MHz and 802 MHz, interfering with other channels.
Therefore, frequency planning and spacing calculations are critical in multi-channel systems.
Other Potential Types of Interference
Pulse Interference
Short-duration, high-intensity pulse signals (e.g., generated by motors, relays, or ignition system switches) create broadband noise in the spectrum, reducing signal quality.
Adjacent Channel Interference
When two devices operate at close frequencies, boundary interference may occur, causing signal overlap or loss.
Multipath Interference
In urban, stage, or densely built environments, wireless signals may reflect off walls or objects, causing delays and phase shifts, leading to signal attenuation or “dropouts.”
Ambient Noise
Various sources, such as LED lights, video processing equipment, or control chips operating at 500–900 MHz, can also contribute noise to a wireless microphone system.
Strategies to Reduce Interference
To enhance the signal stability and system reliability of wireless microphones, the following measures can be adopted:
Frequency Planning
Plan frequencies properly and avoid already occupied bands to prevent co-channel, adjacent channel, and intermodulation interference. (See AMSaudio Wireless Microphone Frequency Planning Technical Manual for details.)
Use Frequency-Hopping or Diversity Receiver Systems
Using systems that support frequency hopping or automatic frequency selection, such as AMSaudio DH6000 series (Digital Hermit), can significantly improve signal stability.
Optimize Equipment Layout
Avoid placing receiver antennas near interference sources. Antennas should be positioned as high, far, and unobstructed as possible to reduce multipath effects.
Increase Signal Strength
Place receiver antennas closer to the wireless microphone usage area to improve signal-to-noise ratio.
Use RF Filters
Select appropriate filters to reduce out-of-band interference and minimize noise caused by strong signals.
Choose the Appropriate Antenna System
Select different types of antennas based on the usage scenario, for example:
AMSaudio SU265 Anti-Interference Near-Field Antenna
AMSaudio GU5090 Active Distributed Antenna
RF Venue RF Spotlight Near-Field Antenna
These antennas can effectively improve signal reception and anti-interference performance.
By implementing the above measures, the risk of interference in wireless microphone systems can be effectively reduced, enhancing audio quality and transmission stability.
In complex operating environments, understanding the sources and types of interference and adopting targeted preventive strategies is key to ensuring the stable operation of wireless audio systems.
This article does not directly cite specific literature. If you need references or research materials to support studies on wireless microphone interference, the following are recommended topics and representative sources in wireless communications, signal processing, and audio engineering:
1.Textbooks on Wireless Communications and Signal Processing
1.1 Wireless Communication: Principles and Practice by Theodore S. Rappaport
A classic textbook in wireless communications covering signal propagation, modulation techniques, and interference management.
1.2 Digital Communications by John G. Proakis and Masoud Salehi
Provides in-depth coverage of digital communication theory and practice, including signal processing and interference.
2.Professional Journal Articles
2.1 IEEE Transactions on Wireless CommunicationsA top-tier journal publishing research on wireless communication technologies, systems, and theory.
2.2 Journal of Audio Engineering Society (JAES)
Focused on audio engineering, including wireless audio systems, signal processing, and interference management.
3.Wireless Microphone Technical Manuals
3.1 Shure Wireless Microphone Systems User Manuals.
Provides technical guidance on interference and signal handling.
3.2 AMSaudio Wireless Microphone User Technical Manual
AMSaudio, a well-known audio equipment manufacturer, offers comprehensive technical guidance for wireless microphones and personal monitoring systems and is the author of China’s wireless microphone industry white paper.
3.3 Sennheiser Wireless Microphone System Technical Information
Covers interference management and system optimization.
4.Academic Conference Papers
4.1 IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP)
Focused on acoustics, speech, and signal processing, including wireless communications and interference research.
4.2 International Conference on Wireless Communications and Signal Processing (WCSP)
Brings together researchers in wireless communications and signal processing to present the latest technical and research advancements.