If you’re just setting up wireless for the first time or if you’re overhauling a complex system that’s been in use for years, many struggle-eliminating fundamentals apply. We all want a solid, reliable system that will serve us for years to come, and we want to avoid crunchy interference and noise and police calls interfering with our wireless signals, so let’s consider a few things and think the process through in order to maximize the quality of the audio that we send through the ether over the airwaves.
Plan, Plan, Plan!
Our first item for consideration is just plain old planning. As is the case with pretty much everything else in life, planning is an absolute must in the domain of wireless systems. When it’s time for us to consider the purchase of a new front of house mixer, for instance, we take stock of our needs — how many signals are coming from the platform? How many discrete mixes must be provided? And we project into the future, will we need more channels in the months/years to come? Are we going to add that extra synth/keyboard station on the platform? An additional electric guitarist? More vocalists? If we’re smart, we will indeed plan ahead — choosing a console that might be more than we currently need, but will perfectly fit the bill on down the road.
This kind of thinking is legitimate by way of wireless too. Do we purchase multiple transmitter/receiver pairs as discrete packages, or do we look into a modular system that will facilitate the addition of more channels as we go? Do we piecemeal a system together one pair at a time, or do we plan for future growth and prepare for our expected needs? As with console planning, an honest and clear-eyed assessment of channel requirements is a key consideration. What’s the absolute maximum number of wireless channels we might need in our current configuration? Vocal mics, body packs for guitarists, pastor headset mics and others figure in. And that’s just the systems that transmit signal from platform to front of house. We must also consider in-ear monitors as well. In fact, we’ll almost certainly need more IEM channels than instrument channels, because certain musicians (drummers, for example) that are lkely captured with wired mics, but may be monitoring via a wireless IEM.
Analog? Digital? So Many Choices
Once we sort out how many channels we’ll need, we move on to researching wireless topologies. Are we going with analog, digital or a hybrid approach incorporating both? We also need to consider potential interference sources. We tend to think first of external signals — local broadcasters, police, commercial, military bands and so on. But if we don’t take care, we may also end up inadvertently interfering with our own signals.
Start out by doing some RF coordination to avoid these pitfalls. First, do some research to determine what frequencies local broadcasters are using, and also the shape of their broadcast contours. This will provide valuable insights on pointing us away from using those frequencies. Yet at the same time, don’t simply trust that the information we find on the internet is accurate or up to date. We need to go a step further and scan the spectrum to see what’s on the air out there. Avoiding interference by way of preventing unwanted signals in our Sunday services is only one of the reasons for pursuing RF coordination with vigor.
Avoid the deployment of systems on illegal frequencies. It’s important to avoid stepping on broadcasts, and it’s equally important to avoid running afoul of the FCC by transmitting signals on unapproved frequencies. Government auctions of bandwidth and shifting of television from analog to digital (and to new frequencies) have changed the landscape, and in the future, the allocation of available bandwidth is certain to continue changing, so paying careful attention to the changes, so we remain legal and in the clear is important. If we get to the point where we are operating with over 50 frequencies, we can apply for and be issued a Part 74 license by the FCC, which can protect our operations, but that’s a much more complex topic for another time.
Ready, Set, Go!
Once we plan out our needs and determine what frequencies we’ll be using, it’s time to deploy. There are a few best practices to which we’ll want to adhere to achieve excellent results. One important consideration is the elimination of RF obstacles. We want to establish line-of-sight between transmitter and receiver unless it’s absolutely impossible. It’s so important that I would respectfully submit that it’s worthwhile to find a way to make it happen even if it does initially appear to be impossible. And not only do we want to make sure there’s open air between transmitter and receiver when we first install, but we want to make sure it stays that way. I was recently in a less-than-optimal situation in which a temporary antenna was placed at front of house. I started hearing interference, and discovered — to my chagrin — that it was being caused by the pastor’s wife standing in front of the antenna. I mustered up the courage to politely ask her to move, and the interference stopped. The lesson is to not presume that because we have line-of-sight at first that it will remain that way permanently.
Antennas and More
We need to use the right antenna for the job, and we need to use the right antenna the right way. Some antennas are directional, others are not. It’s important that they be deployed as per the manufacturer’s directions. Remember, for instance, that diversity antennas must be a minimum of ¼ of the wavelength apart in order to function properly. Similarly, it’s not a good idea to have an “antenna farm” crop up. Antennas interact with each other, and can cause problems. Similarly, multiple transmission frequencies interact with each other (they “intermodulate”), causing intermodulation distortion, which creates RF energy at unexpected frequencies. It is for these reasons that you will want to scan the RF energy in your space especially after you have deployed and powered up all your transmitters — they may be interacting in a way that causes problems.
Other important considerations: make sure you’re sending a solid signal. Getting the RF part of the big picture right is important, but you’ll also want to make sure you’re sending a good, solid, properly gain-staged signal over your bolted-down RF. Sending a weak signal means that additional gain will need to be applied on the receiver end, resulting in additional noise in your mix. Also — make sure you’re managing batteries properly. Most churches are now using rechargeable batteries, and that’s very smart — but if there’s no obvious way to distinguish charged batteries from discharged batteries, it’s not so smart anymore.
One final out-of-the-box solution that is worthy of consideration (and one that I frequently recommend) is to simply avoid wireless altogether in applications for which it is not necessary or beneficial. The example I typically trot out is using a bodypack for a drummer’s IEMs. The drummer is in a fixed location, and it’s almost certainly plausible to send monitor signals via wire to them. By doing so, we avoid the additional challenges presented by wireless systems, and help ensure that our drummer (or keyboard player, etc., etc.) has nice clear monitoring.
Wireless is a wonderful, magical technology that has transformed the world of musical performance and AV, and it’s worth taking time to get it right so it’s legal, beneficial, and excellent. Take your time and do it right!
John McJunkin is the chief engineer and staff producer in the studio at Grand Canyon University.
