Roughly a year ago, I started writing this monthly House of Worship column for FRONT of HOUSE. One of the first articles I wrote was about wireless, so it only stands to reason that coincidentally, a year later, I’m revisiting the subject to provide some additional insights that will hopefully improve your wireless operation.
I recently visited another church that reached out to me for wireless help, and sure enough, they had 1/4-wave antennas remotely mounted roughly 25 feet from their receivers. Before I arrived, they thought they would have to replace all of their wireless. Instead, they invested less than $600 on a new set of antennas, a robust set of coax and some mounting hardware, and soon, their eight-channel system was fully functional and very stable. With wireless, it’s often the little things that add up to big problems.
Seek (Frequencies) and Ye Shall Find
I often encounter people who are unaware of available free RF tools like Sennheiser’s (Fig. 1) and Shure’s online frequency finders. These should be your first stop in the quest for clean frequencies. If you aren’t familiar with how these work, it’s a fairly basic process. You enter your address or zip code, hit search, and the website returns a list of frequency bands (typically displayed in 6 MHz chunks) that are in use by TV stations, frequency bands that are vacant and frequency bands that are illegal for use with wireless microphones. Don’t assume that you can’t use your wireless in 6 MHz bands that are occupied by TV stations. In fact, in most cases, you should seek out frequencies that are occupied by distant, low-power television transmitters that are unlikely to interfere with your wireless microphones (or vice-versa).
Coordination and Monitoring
One of the most significant advantages to current wireless systems is the coordination and monitoring software provided by various wireless manufacturers. Shure’s Wireless Workbench and Sennheiser’s Wireless Systems Manager are two of the most common, but every major wireless manufacturer has their own version of this type of software. Some of the features of such software lets the user:
• Scan the wireless spectrum for clean frequencies, and deploying clean frequencies to receivers one at a time, or in bulk. Note: The scanning feature does require you to be connected to at least one receiver in most cases. Your computer alone cannot scan the RF spectrum without some sort of hardware.
• Coordinate intermodulation-free frequencies between disparate systems, such as wireless microphone, IEM, intercom and instrument wireless
• Monitor RF and audio levels for each transmitter/receiver combo, as well as battery levels for transmitters and receivers, and
• Change receiver settings such name, output gain and squelch level.
Antenna Usage and Placement
Contrary to popular belief, in most cases antenna selection and placement is not that difficult if you follow a few simple rules. The number one rule is “line of sight.” Placed above your congregation, your antennas should be able to “see” the transmitters. Otherwise, much of the transmitted RF energy will be absorbed before it reaches your antennas, making dropouts more likely. The second rule is to keep your antennas away from metal objects and avoid mounting them inside of racks with a ton of other gear. Third, the little quarter-wave antennas (as shown in Fig. 2) that came with your wireless system, are not supposed to be mounted remotely. Attach them directly to the BNC connectors on the receivers themselves. If you require remote antennas — because, for example, your wireless receivers are in a backstage closet — use half-wave (such as Fig. 3) or LPDA “shark fin” style antennas that can be mounted remotely.
Gain Structure
One of the most commonly overlooked aspects of using wireless systems is gain structure. Even among skilled engineers who fully understand the importance of gain structure on a mixing console, the concept seems lost on many in the wireless world. Similar to setting gain structure using your console’s preamp when using a wired microphone, setting the sensitivity of your transmitter to suit the input signal prevents clipping and improves the system’s signal-to-noise ratio. If you have a really strong vocalist, watch the audio level on the receiver when they are really belting out a song. Are they clipping? If so, dial back the sensitivity so they have some headroom before clipping. Don’t go too far however, or your signal-to-noise ratio will suffer.
Battery Management
For as long as I can remember, our church was using traditional alkaline batteries from Energizer and Duracell in our wireless systems. Not only was it very expensive each year, we were generating a lot of battery waste that needed to be recycled, which was an additional expense. At the time, I simply didn’t trust rechargeable batteries, and I had a few bad experiences when using them over the years. A few years ago, we switched over to rechargeable nickel-metal hydride AA’s, and we haven’t looked back. It does require a bit more management to deal with rechargeables, but we have a charging station set up in my office, and now it is a part of our weekly workflow. In fact, it’s amazing how long these things last! We bought our first set of rechargeable batteries more than two years ago, and they are still going strong. They don’t quite last as long as they did when we got them, but they are still more than sufficient for a Sunday morning.
Speaking of Sunday Morning
When you walk in the door on Sunday morning and start firing up your system, take a quick glance at your wireless receivers. Notice anything unexpected? Notice any RF energy on channels that are typically clean? Even worse, do you see meters on your mixing console lighting up with audio level when none of your transmitters are turned on? If so, it might be time to run a quick scan and deploy new frequencies. With wireless, a little bit of vigilance goes a long way towards ensuring smooth operation each and every Sunday.
Vince Lepore is the technical director at St. Luke’s United Methodist Church in Orlando and teaches live production at Full Sail University
