Tel: 905–690–4709 dk@tfwm.com - Darryl Kirkland, Publisher

Frequing Out

We tip our top hat to improvements in wireless technology. Wireless microphone technology has come a long way. And the church is better off as a result. I remember seeing a picture and short story from a very early radio broadcasting magazine. The picture showed the earliest wireless microphone I have seen. An NBC radio reporter, dressed in tuxedo, tails and a top hat, was reporting directly from New York’s Easter Parade. He was holding a carbon microphone mounted atop a wooden handle and his belt was loaded down with heavy batteries and a vacuum tube transmitter. The antenna was built into the top hat. It was Day One of the wireless microphone age and already the benefits of mobility were being weighed against the trade-offs of cost and performance.

Fast forward to the late 1960’s and I was having my first experiences with using wireless microphones in the church. There were few brands to choose from then and fewer that were anywhere near reliable. For an outlay of about $1500 we got a single-channel bodypack transmitter with a lav and a non-rackmountable, non-diversity receiver. If we were very careful with it, it worked some of the time.

As late as the early 1980’s, the head of audio for CBS Radio in Washington, DC, told me, “There is no way I would use wireless if I can use a wired mic. I wouldn’t put a wireless mic on a reporter jumping out of an airplane if I could feed a wire out to him fast enough.” That was how this veteran audio engineer felt about dealing with wireless at that time.

But improvements in technology have made wireless mics commonplace in both broadcasting and sound reinforcement. Does it still cost more to add an FM radio transmitter and receiver to a microphone than it does to feed a signal down a mic cable? Of course it does. Are the specifications of a high-performance, hard-wired microphone still likely to exceed those of the same capsule in a wireless package? Yes. But the cost-to-performance ratio, the value, has improved dramatically.

The technology available in today’s wireless microphone systems has given us performance, reliability, flexibility and convenience that was simply not available only a few short years ago. The integration of large-diaphragm condenser elements, from some of the most popular studio microphones, into some handheld wireless systems has brought studio quality sound reinforcement much closer to reality. A few systems now feature dual compander circuits that can process high and low frequencies independently, eliminating the artifacts of common single compander circuits. Battery powering systems are offering some very respectable battery life, and are providing excellent performance from low-cost AA cells. Some new systems even send data about the transmitter, including battery condition, back to the receiver for monitoring by the technician at the console.

But even as wireless performance has been improving, the RF spectrum, within which lie the bands used by wireless mics, has become increasingly crowded with all those wanting a piece of the airwaves. Wireless mics operate in the same bands as TV stations. The FCC now requires all television stations to broadcast a digital (DTV) signal in addition to their existing analog broadcast (NTSC signal). To accomplish this, the FCC has assigned an additional, temporary TV channel to each station, meaning that much of the bandwidth wireless mics are permitted to use is now tied up with TV signals. (After December 31, 2006, each station will choose which channel it wants to continue using, freeing up the other theoretically for wireless use.) Worse, the digital signal crowds out wireless even more than does analog: While an analog TV broadcast leaves open spaces called “guard bands” between stations and space between the color, picture, and sound subcarriers spaces that allow wireless mics plenty of room to transmit DTV signals hog the entire 6 MHz spectrum, leaving nothing for wireless.

Often, a single-channel wireless system, that has served a congregation for years, has been instantly turned into a useless relic by a television station going digital, or even by another wireless system in local use. More advanced, frequency agile systems, wireless mics that offer multiple, selectable frequencies, present at least a partial solution. If your church uses one or just a few wireless mics, and they are frequency agile, you may find it easy to select a new frequency for any unit that suddenly gets stepped on by outside forces.

But many of us are using greater numbers of wireless systems than ever before. And as that number increases, so does the complexity of managing the frequencies. Heaven help you if the churches on the other three corners of your intersection all have large music ministries that refuse to be tied down by mic cables. Visiting music groups are likely to bring in their own wireless systems. Again, frequencies must be coordinated between their systems and those of the church if both sets of mics are to be used in the same service. Frequency coordination is not a new problem. For years, broadcasters have organized frequency coordination committees to handle the problems that arise when news or sports crews converge on the same events.

Not only do all wireless systems that are within each other’s RF coverage area have to be on different frequencies, but the fact that the frequencies are different doesn’t ensure they are compatible. That is, one transmitter can interfere with another even though their frequencies differ. The manufacturer of your wireless microphone is likely to offer assistance in selecting frequencies that are compatible and are not in use by local TV stations. Most provide a chart for frequency selection, either in a printed manual or on a Web site, or perhaps both. Audio-Technica’s interactive online chart, for example, allows you to select the system and enter your ZIP code for a table of suggested frequencies in your area.

If you don’t have access to such a chart, here is a fairly simple and reliable technique for frequency selection, but it requires that your units have some kind of RF level meter (most of the better ones do). First, turn on a single receiver, leaving all transmitters off. Scroll through the tuner’s range, watching the RF meter as you cross the band. Whenever you see a frequency with little or no RF activity, you have likely found a clear channel. Find the one with the least activity, and set both the receiver and the transmitter to that frequency, leaving both on. Next, turn on another receiver and repeat the process, finding a clear frequency for it and setting both receiver and transmitter. Do this with each receiver until you have set all. To double-check your work, turn each transmitter off, one at a time, and make certain that the corresponding receiver squelches or mutes, or the RF level drops very low.

Once you have your frequency plan, make a chart of each unit in the system and the operating frequency. While you’re drawing up this chart, get in touch with other nearby churches to ask what wireless frequencies they may be using. They should be cooperative; after all, it’s just as handy for them to know about your wireless system as it is for you to know about theirs. Add a chart of the frequencies being used by others in the area, so you can dial around them as needed. By keeping in touch with other nearby wireless, you can help ensure that you are notified when new systems come in to crowd the bandwidth. Be sure to initiate contact with any new churches that come along, too.

Managing all your wireless frequencies can be a daunting task, but it is a necessary and worthwhile one to keep your system running optimally. Fortunately, new technology is addressing this task, as well. Wireless receivers are now available that will scan the band in which they operate for frequencies already in use, and set their own frequency between those detected. Once you have set one receiver, you will need to set the frequency of a transmitter to go with it. Then leave that transmitter on as you have the second receiver scan. It will bypass the first frequency and any others in use and lock on to a new frequency. Repeat this process for each receiver in your system and you should be in good shape.

Simpler yet, a feature called IntelliScan, available on Audio-Technica’s Artist Elite Wireless 4000 and 5000 Series systems, allows the receivers of either series to link together. You perform the scan using just one receiver. It automatically senses all frequencies in use on the band and sets all the linked receivers to the best available frequencies, also avoiding incompatible frequencies. No charts needed. If a visiting musician’s wireless might interfere with one of yours, a quick scan will move your receiver to a safe frequency. You then simply scroll up or down on the frequency selection buttons of the appropriate transmitter to the new frequency. Hit the Store button. You’re done.

Wireless has indeed come a long way. The best of recent wireless technology offers unprecedented sonic performance and greatly simplifies the otherwise complex task of frequency coordination. Both areas should be important to achieving the goals of any technical ministry.

Powered by