Introduction to Wireless Microphone Systems

Wireless equipment is perhaps one of the most poorly understood technologies used in the theatre and broadcasting world today.  Despite their complexity, it is possible to develop an intuitive understanding of how these devices work.  The purpose of this document is to explain the fundamental behavior of wireless systems, and to apply this knowledge to the functionality of wireless microphones, wireless in-ear monitors, and similar systems commonly found in the theatre and broadcast industries.  This guide assumes that the reader is familiar with basic electrical concepts such as impedance and electrical waves.

A wireless system is a communications system that transmits data from one device to another without the aid of wires or cables.  Data does not necessarily imply that the system is digital; analog audio is considered data as well.  Typically, these systems consist of radio-frequency devices, meaning that they use radio waves to communicate.  Less frequently, devices use infrared or visible light to communicate.  An example of infrared devices are television remote controls.

All RF, or radio frequency, devices transmit an electromagnetic wave that oscillates a specific number of times per second.  This property is called the wave’s frequency.  Wireless microphones and in-ear monitors operate at or around a frequency of 600 MHz, meaning that the wave that a wireless microphone emits goes up and down 600 million times per second.  The frequency of a device determines the characteristics of the signal, and generally speaking, lower frequency devices transmit much farther than higher frequency devices due to attenuation (weakening of the signal).

A wireless system usually consists of a single transmitter, and any number of receivers.  The transmitter generates the RF signal, and with the help of an antenna, launches the wave into space.  The receiver captures this wave with the help of an antenna, and turns it back into the information originally transmitted (or something very close to the original information).

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