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Why Wireless?

John McJunkin • October 2019Sound Sanctuary • October 14, 2019

Shure’s Wireless Workbench software provides a powerful package for RF optimization.

There are numerous great reasons to use wireless mics, instrument transmitters and in-ear receivers. Let us count a few. For one, it’s really nice to eliminate the clutter (and hazard) of cables running all over the platform. Even when cabling is well managed, it’s unsightly, and it’s a virtual inevitability that someone will trip over a cable or kick a connector and cause a disaster. Cables also limit the physical placement of things. A mic cable is a leash — it limits the mobility of the person using it. Same with a cable plugged into a guitar. And that pulpit that must be moved into and out of position during the service? Yep — if it has a wired microphone, that can cause problems too. So we go wireless. It’s impossible to trip over RF energy, and RF energy also happens to be invisible, so it doesn’t add to the visual clutter of the platform.

‡‡         Planning

Do some planning before investing time, money and effort. In the case of wireless, it’s not just a helpful hint — it’s a necessity. When purchasing a mixer, we think ahead. How many channels do we need, both now and in the future? The same principle applies in terms of the numbers and types of transmitters/receivers necessary to accomplish our goals. Chances are, we’ll want three to five handheld wireless mics on the platform for principal vocalists. Nowadays, it’s also likely the lead pastor will need a wireless system for either a handheld, headworn or lav mic. And there may be a need for a roving wireless handheld or two, along with transmitters for guitarists and possibly even remote keyboards. It’s clear the number of human-carried transmitters can mount up pretty quickly. But wait — we haven’t even mentioned the receivers toted around by people on the platform. In-ear monitors have become very common, and with the occasional exception, most are fed by wireless receivers. It’s clear that even a modest wireless system for a typical house of worship can feature a dozen or more transmitter/receiver pairs.

‡‡         Frequencies, Power, Interference

Once we determine our current requirements (and make a few predictions about future needs), it’s just a simple matter of purchasing systems, installing them, and then making sure all our devices are on different channels, right? Partially, but there’s much more to it than that. We need to ensure that we are operating legally, within the statutory confines spelled out by the Federal Communications Commission. They determine what frequencies are available to use and establish limitations on how much power we can radiate with our systems. We simply can’t have a Wild West free-for-all — we don’t want one organization’s transmitters encroaching on the frequencies we’re using, nor do we want our own transmitters encroaching on others.

These days, as the amount of available bandwidth seems to shrink, wireless manufacturers have developed clever new ways to leverage the shrinking spectrum we’re afforded. Go online and see what frequencies are being used in your geographical area — particularly television stations, which live in the same frequency range as our wireless systems. It’s also virtually a necessity to use an RF spectrum analyzer (typically with accompanying computer software) to scan the range of frequencies we may be using to see what is actually happening in reality, not just what frequencies the FCC tells us are in use. And you’ll want to do this before you even purchase your systems — as each is relegated to a certain range of frequencies, you need to know what frequencies to avoid. The other important reason to engage in RF coordination is that certain conditions can create a phenomenon known as intermodulation distortion. It can be caused by poor quality equipment, active antennas or too little distance between transmitter and receiver, and here, an RF spectrum analyzer provides a huge benefit.

‡‡         Antennas

The proper choice and use of antennas may very well be the single most important factor in getting wireless right. Of course, we need to choose unused frequencies and all, but proper execution with the antennas is what really determines success. The key to success here is encompassed in three words… line of sight. Keeping the transmitter and the receiver in line of sight with each other will go a long way toward ensuring a solid and consistent signal. This means getting antennas up above the heads of the congregation so we don’t suddenly lose our signal when the congregation responds to the invitation to “Please stand for the prayer.” Similarly, the lead pastor is somewhat likely to have his or her body pack attached to their posterior, so it might be a good idea to locate the receiver antenna associated with it behind them on the platform. Avoid the “antenna farm,” in which dipole (whip) antennas are all grouped together behind a rack full of receivers. They can actually interact with each other and cause problems. Diversity antennas should be physically separated by at least one quarter of the frequency’s wavelength and angled at 90 degrees from each other to maximize diversity.

‡‡         Battery & People Management

There simply is no excuse for a wireless problem resulting from batteries dying. Good quality rechargeable batteries are affordable, even for the tiniest of churches, and a simple management process can be executed to ensure that plenty of fresh batteries are available every time they’re needed. Dying batteries should never interrupt signal flow. Nor should we ever lose signal because a musician or vocalist has turned off a transmitter, deliberately or inadvertently. We have a multitude of transmitter batteries available, so I encourage locking transmitters into the “on” position, either via electronic means, or by physically blocking the power switch (with tape, for instance) so the user simply cannot turn them off. This may simply be a matter of having the tech staff turn the transmitters on and training users to not touch the power switch. Another thing we might want to instruct handheld mic users to do is to avoid holding the mic at its lower extreme. This is typically where the internal antenna is located, and the RF energy can be blocked by human flesh (of course, the user should also avoid holding the mic too close to the capsule, since this can turn a cardioid mic into an omnidirectional one). Similarly, the little rubbery antennas associated with body packs should not be wound or scrunched up in any way. Another user issue involves personal electronics, like mobile phones, smart watches and so on. No one should take these on the platform to begin with, but if they do, interference can create noises we don’t want in our mix.

Planning, RF spectrum analysis, proper antenna placement, good battery management, and effective personnel training all contribute substantially to good, solid wireless performance.

John McJunkin is the chief engineer and staff producer in the studio at Grand Canyon University.

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