AV Technology - May 2008 - (Page 74)

avmo USING WIRELESS MICROPHONES Get the most out of these extremely convenient tools. W ireless microphones offer extreme convenience, freedom of movement, and simplicity. But they are not without some pitfalls. Here’s how to use them properly to maximize these benefits for your application. ABOUT FREQUENCIES There must be one transmitter and one receiver to make a complete wireless system, and they both must be on the same frequency. The FCC controls which frequency ranges can be used by wireless. In the US, the frequencies used for wireless audio systems are: low-band VHF (49-108 MHz) high-band VHF (169-216 MHz) low-band UHF (450-806 MHz) high-band UHF (900-952 MHz) UHF systems tend to perform better than VHF systems. Wireless frequencies are shared with TV stations, communications equipment, and other wireless mic systems. Because of frequency sharing, chances are someone else in the area might be using the same frequency as your wireless system. Government regulations also set other technical requirements, including limits on maximum transmitter power. If any two transmitters are operating on the same frequency, interference will result and the wireless system will be unusable. Two transmitters cannot be used with one receiver at the same time. A higher squelch setting on the receiver provides better protection against interference, but can cause a reduction in operating range. Set squelch to the lowest position that reliably mutes the interference. Turn off unnecessary electronic equipment, especially computers, CD players, and other digital devices. These are a relatively common cause of wireless interference, especially if they are near the receiver. If the use of computers or digital devices is necessary, keep them at least 3 feet (1 meter) away from the wireless receiver and its antennas. The practical maximum operating range of a wireless system will vary from as little as 100 feet in heavily crowded indoor situations to approximately 1,000 feet under open outdoor conditions. Diversity systems will almost always have better operating range than non-diversity systems. Receivers must have either one or two external antennas, and there should be a clear open-air path between these antennas and the transmitter. TIPS FOR NOVICE USERS 1. Inform the presenter that the sound engineer will take care of turning the mic on and off. Tape down the on/off switch on the transmitter so they can’t even try it. 2. Give some thought as to which way the presenter is most likely to turn his/her head when addressing someone else on the stage or in the audience. If it’s not feasible to center the mic on a tie or shirt, then choose the side/lapel in the direction the presenter is most likely to turn his/her head. 3. Excess lavalier cable should be secured out of the way so that it can’t become tangled on a chair arm or podium light. A little gaffer’s tape or “bobby pin” is great for making sure this cable stays where you want it. 4. When possible, the transmitter/ beltpack should be clipped to the presenter’s belt or waistband — not dropped into a pocket. You don’t know what else might be in the pocket. If the presenter sticks her hand into the pocket she may accidentally disconnect the mic or hit the on/off switch. 5. One of the major benefits of wireless mics is freedom of movement, but novice users may be tempted to move too much, and can find themselves in front of loudspeakers, causing feedback problems. Always inform mic users about avoiding proximity to loudspeakers. 6. If the presenter must wander around or present from several places on the stage or in the room, tell him what to do if he encounters a signal drop out. Even the highest quality wireless mics may encounter dropouts. Just a step to the side, or even a little shuffle, may solve the drop out so that the presenter can continue with minimum disruption to the show. Sources: Audio-Technica, Shure, Harrison Brothers. ABOUT BATTERIES 1. Weak or worn-out transmitter batteries are a common cause of wireless problems, including complete failure, poor range, distorted audio, and interference. 2. Use high-quality, fresh alkaline batteries. Most other types (e.g., zinc-carbon) will have a much shorter life. 3. If there is any doubt about the condition of a battery, replace it. Make certain that used batteries are never mixed with new ones. 4. Considering re-chargeables: • If you must use re-chargeables, use longer-lasting NiMH, Li-ion, or Li-polymer, not Ni-Cd. • Pay attention to actual voltage. Some rechargeable batteries packaged as 9 volt may only produce 7.2 or 8.4 volts — or, worse, 9.6 volts. 74 | AVTECHNOLOGY | may 2008 www.avtechnologyonline.com http://www.avtechnologyonline.com

Table of Contents Feed for the Digital Edition of AV Technology - May 2008

AV Technology - May 2008 Contents Precedent Corporate: How to Qualify an AV Supplier Education: Working Smarter AV Technology's Guide to Networked AV Government: IPv6 — Why You Should Care Calculating ROI on Your Digital Signage Investment Enhancing Audio in the Classroom Minimizing Equipment Theft Smart AV The Tribe Has Spoken AV Enables Interactive Research AV Image Enhancement Product Spotlight Tech Horizons Product Review New Products AV MO

AV Technology - May 2008

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