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The Mystery of the Missing Wireless Signal

I've heard some people say that wireless DMX had failed them, only to find out, after extensive questioning, that they didn't understand the technology in the first place, which is why they didn't get good results. When I hear something like that, I'm always skeptical because today's state-of-the-art technology works well. It uses techniques like adaptive frequency hopping spread spectrum and redundancy, and as long as you know certain things about setting up wireless DMX, you will get it to work sooner or later. So when someone says it doesn't work, I start asking questions about how it was set up, which products and frequencies were used, and the transmission distances involved.

Take, for example, the guy who told me they tried using wireless DMX at a festival and it didn't work at all. After a short interrogation, we identified the issue.

"How far were you transmitting?" I asked.

"Not that far," came the reply. "It was about 900 meters."

Under the best of circumstances, wireless DMX, like WiFi, will travel about 50 to 100 meters, depending on the frequency it's using, unless you use a directional antenna, in which case it can travel much farther. If there is a clear line of sight with no obstructions, then you can transmit 900 meters with no problem. But unless you know that, chances are you aren't going to stumble across those conditions.

Recently, a friend was setting up a wireless DMX system and she was having trouble. Even though she had done her homework and was very careful to set everything up properly, some of the receivers were not getting a signal. It was a real mystery.

The system was set up outdoors for an architectural lighting installation, and she had several receivers that were working just fine and some that were not. She tried using a WiFi scanner to check the signal strength, and she could see that the signal was not reaching some of the receivers but she could not figure out why. She reached out for help, and I offered several suggestions, like checking for interference, but none of them seemed to be the answer. Finally, after talking to the manufacturer, they figured out that one of the transmitters was very close to a steel beam, which caused the signal to reflect in such a way that it did not reach the receiver.

Wireless DMX is enigmatic. You can't see it, feel it, hear it, or smell it. It is the modern day equivalent of electricity in the early 20th century. People didn't electricity in the early days, and therefore some people didn't trust it. Many people abused or misused it, resulting in many electrical fires.

Fortunately, the consequences of misusing wireless are much less severe but it can still be frustrating when you can't seem to get it to work right. There is a lot to know about wireless, and the more you know, the more likely you are to get good results. Whatever you know about wireless, it might help to think about its similarity to light. Like light, it is electromagnetic radiation, except it has different wavelengths, and like light, it follows the inverse square law. Light behaves both like a wave and a particle, as do wireless signals. Obstacles can partially block wireless while other objects reflect it, particularly those made of metal.

To visualize wireless transmission, imagine you have a 100 milliwatt light bulb, like an indicator light. The closer you are, the better you can see it, and the farther away you are, the more the energy spreads and diminishes. Other lights can overpower it and wash it out. And objects in its path can seemingly make it disappear altogether. That's what happened in the mysterious case of the missing wireless signal.

In a perfect world there is a clear line of sight between the transmitter and receiver with little or no interference. In the real world, there is almost always interference to some degree or another. Most wireless DMX can deal with it very well but you can better the odds of having a reliable system by better understanding the ins and outs of wireless.

There is a lot to know about wireless, including that fact that it is here to stay. We're only in the beginning stages of the wireless era. Both Lumen Radio and W-DMX are now offering wireless receivers on a chip that are very small and inexpensive. Soon wireless DMX will be a standard feature on every automated light and LED fixture. Be prepared for the coming wireless revolution by arming yourself with information and knowledge, from the fundamentals to the latest technology.

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