Wireless Microphone Basics

If you need to move around the room during your presentation, you will need to go wireless with a couple of components, namely an unwired remote control — and a wireless mic. We’ll talk about remotes some other time, but we’ll get into the wireless mic solution right now.

Wireless microphone systems, of course, eliminate the cable that connects a microphone or musical instrument to a sound system, allowing the user to move around without restraint. In a typical setup, one wireless system is required to replace each standard wired microphone or instrument pickup; in a band situation, the signals need to be separately routed into the mixer to control volumes individually.

However, we are concerned here with presentations, not musical performances. In most presentations there will be one speaker, perhaps two, thus only a wireless system or two is needed.

The Signal Chain

A wireless system has three main components: an input device, a transmitter and a receiver. As previously mentioned, musical instruments can be connected wirelessly, too, but for our purposes the term “input device” means a microphone — a handheld, “vocalist” type mic, or even a clip-on “lavalier” model. It provides the signal that will be sent out by the transmitter component and, in the last process, received for amplification and projection by the sound system.

The microphone plugs into a transmitter that converts the audio signal into a radio signal and broadcasts it; there may be an antenna visible on the transmitter or it may be concealed inside. Depending on conditions, the signal can travel from 100 to over 1,000 feet, depending on conditions.

While there are some transmitters that regular microphones can be plugged into, transmitters are usually built into the handle of wireless microphones, making them only slightly larger than standard wired microphones. Most wireless mics require a 9-volt battery to operate.

Last Link in the Chain

The job of the receiver component is to pick up the signal from the transmitter and convert it back into an audio signal; in fact, the output of the receiver is electrically identical to a wired microphone signal, so it can be connected to a standard microphone input in a sound system.

Wireless receivers are available in two different configurations. Single antenna receivers, with one receiving antenna and one tuner, work well in many situations, but are often subject to momentary "dropouts" of the signal as the person with the transmitter moves around the room. Specially made “diversity receivers” usually provide superior wireless performance, as it uses two separate antennas and (usually) two separate tuners. A certain circuit in the receiver automatically selects the better of the two signals, or in some cases a blend of both, as one of the antennas will likely be getting a clean signal at any particular moment. The chances of a dropout, therefore, are dramatically reduced.

Most wireless receivers operate on AC power, although there are some small, battery-powered models available that are primarily used for portable use such as mounting to a video camcorder. In presentation-type use, the receiver would be sitting next to either the projector or a powered mixer, depending upon which sound system is being used.

Whatever sound system it is, the receiver simply plugs into the appropriate input, which on most units means plugging in the receiver’s ¼” phone plug. If the sound system you are using has only XLR connections for mics, a simple adapter can make your last link a quick one.