I'll just start right out by revealing that the "secret" really isn't all that much of a secret, but instead, a set of well-tested fundamental principles and best practices that yield consistent reliable results. Rarely do I see all of these things put into practice in one place. As a result, there may be those who feel that wireless mic installation, setup, and use involves black magic or voodoo of some sort. To the contrary.
First is receiver antenna placement. Diversity reception is very important, thus receiver antennas should not only be line of sight to the transmitters, but placed high and spread wide—at least 10 feet apart, and 15 feet is even better. Many theaters place the antennas on opposite sides of the proscenium so that at no time are any transmitters body blocked from both antennas.
Next is RF band planning where the mic RF channels are in one frequency range, the IEM channels in another, and the COM channels in another, for starters. This reduces interactions between the groups, reducing dropouts and audio noises. Frequency coordination is next. This is a mathematical calculation including all proposed frequencies and external sources like TV stations so that they do not interact with each other via direct interference or via intermodulation products. Various software packages are available to do this.
Audio gain structure is also quite important for wireless mic system setup, just as it is for the rest of the audio system. Instead of "just" a microphone, where there is one initial gain at the front of the mixer, with wireless mics you add two more gain stages—at the transmitter input and at the receiver output.
Take care of these things and you should be in great shape.
Karl Winkler is Director of Business Development for Lectrosonics. This feature is part of SCN's "Hush Hush" October print issue.