I don’t know why, but things seem to come in waves. Lately, the wave has been wireless mic’s. I’ve heard from several people who are having trouble with their systems, and most of the problems revolve around two main issues; improper design & installation and frequency coordination. Today, we’ll tackle the first issue; next time we’ll hit the second one.
Wireless is harder than you think. Once you move beyond one or two channels of wireless in a building, you need to make sure things are designed to work together and are installed properly. While it’s true you can stack a bunch of receivers with their 1/4 or 1/2 wave antennas at FOH and they will work—some of the time—it’s not the right or best way to go.
And as an aside, the plural of antenna is antennas. Bugs have antennae, wireless mic’s don’t. Antenna, antennas. Got it? Ok. Moving on.
The problem is, once you start putting all those antennas next to each other, they start causing interference with each other. Fire up enough channels and you are sure to have issues.
The answer is proper antenna distribution and combining. A lot of people get confused on these two terms, so let me start by defining them. Antenna distribution is used for wireless mic’s. Basically, you take a couple of specialized antennas—usually using long periodic dipole arrays (LPDA), AKA paddles—spread them out so they cover the intended area and run them into an antenna distribution system. Most antenna distributors will output the signal to 4-8 wireless receivers. They typically have a cascade out to connect to a second distro in case it’s needed.
An antenna distro will cost anywhere between $1,000-3,000+ depending on the system. Some will say, “But Mike, those are so expensive!” Yes. They are. Wireless is hard. And expensive. That’s why we wire everything we can. And there is no sense spending $10,000 on wireless mic’s but trying to save $2,000 on antenna distribution. The system simply won’t work well. Do it once, do it right.
When it comes to wireless IEMs, you are dealing with transmission antennas. That means you need an antenna combiner. The combiner is similar to a distro, only in reverse. It takes the outputs of 4-8 IEM transmitters, and combines them into a single antenna signal that goes out to the antenna itself.
Like distros, combiners are expensive. If you want to do more than a few channels of wireless IEM’s, you’ll have to get over that and pony up. You also need to use the proper paddles. You can’t use an active paddle with an antenna combiner as it’s a transmit antenna.
Use the right antennas, cable and settings. It’s important to note that while wireless antenna systems use BNC connections, they don’t usually work well with video cable. Antenna cable is 50-Ohm; video is 75-Ohm. Use the right cable. If the cable runs get long, you’re going to want the expensive RG-8 (or better) cable to minimize loss.
And don’t assume that when using an active antenna that the +10 dB setting is better than the 0 dB setting. Follow the manufacturer’s recommendation and use the setting to compensate for the length of cable only. Setting the gain higher than necessary only increases RF noise and reduces performance. Use the minimum number of antennas you can to get the coverage you need. More will only cause you grief.
Talk to the right people. When building wireless systems, the best place to start is the manufacturer. They want their equipment to work and all have tech support departments who will help you get the right equipment, offer advice on installation and design. Reputable integrators are another great source of help. Third party companies like PWS are also great resources.
The bottom line is that wireless is hard and expensive. I cringe when I hear of churches putting drummers on wireless IEMs. Or wanting to have 30-40 channels in their main room so everything can be wireless. Even stuff that doesn’t ever move. And because they want to do it on the cheap, they wonder why it doesn’t work.
You can do hundreds of channels in a room (consider the Super Bowl). But it takes a lot of work, specialized equipment, people who really know their stuff and expensive wireless gear. Wire what you can, and make sure your wireless system if of good quality, designed well and installed properly.
But even then, you still have to do proper frequency coordination. And we’ll tackle that next time.