Wireless DMX transmission has been around for several years, and it keeps getting better by taking advantage of improvements in wireless technology. In the last five years, it has become more reliable, easier to implement, and less nerve-wracking than ever before. In my experience, those who argue that wireless DMX is unreliable are typically reflecting on a bad experience they had with it several years ago. If you give the current technology a try, chances are you will not be disappointed…
A technique known as frequency-hopping spread spectrum (FHSS) transmission differs from fixed-frequency transmission in that the transmitter and receiver are not set to a single frequency, as is sometimes the case with wireless microphones. Instead, the carrier signal ranges from 2.4 GHz to 2.4835 GHz, which is known as the ISM band (industrial, scientific, and medical), or from 5.47 GHz to 5.725 GHz, which is known as the U-NII band (unlicensed national information infrastructure).
The bandwidth of transmission is less than 1 MHz, so several hops can be made inside each range of frequencies. Depending on the manufacturer, the number of hops can vary from tens to thousands of hops each second. The maximum refresh rate of DMX is 43 Hz, which means that most wireless DMX systems are easily capable of transmitting the maximum number of data packets with plenty of room to spare. If there is any loss of data or data corruption, the data will be refreshed quickly enough that the error will most likely go undetected by the user.
FHSS offers a variety of advantages over fixed-frequency radio transmission. It helps make it more immune to interference by spreading the energy over a range of frequencies so that any narrowband interference has less of an impact on the entire transmission signal. It also allows a transmission to coexist with other devices in the same transmission band and still operate effectively.
Richard Cadena, "Focus on Fundamentals," PLSN, Dec. 2010.
