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Wireless World: B A C to Basics

Isn’t it amazing that a wireless lapel mic system actually contains six wires: a mic wire, a transmitting antenna wire, two receiving antenna wires, a power wire, and a signal wire? A wired mic, on the other hand, only has one wire! Marketing truly is a wonderful thing.

The inaugural issue of this column described most wireless transmission troubles as the result of RF interference or problems with the batteries, antennas, and connectors of the unit. Careful attention to the following will eliminate the most common problems.

The Achilles heel of every wireless mic system is its battery. The most complex audio system can be rendered useless by a drained two-dollar nine-volt. Since Murphy invented batteries, their exact moment of failure is timed to coincide precisely with the most important moment of the service. In light of this fact, it makes sense to put a new battery in the transmitter each time the unit is used for a service. The manual may claim a life span of fifteen hours, but the true life may be a few as four hours. Used batteries may then be placed into hearing assistance receivers, nursery pagers, and children’s toys to extend their benefit.

The dissipation curve of wireless systems places a heavy drain on the battery and most nine-volt systems will not operate below 6.8 volts, resulting in a shortened life span. It is not advisable to use Ni-Cad rechargeables, due to their inability to charge up to the standard nine volts of an alkaline battery. To receive the best service, purchase only commercially rated batteries, such as Duracell’s Procell series from companies such as Jireh Supply at (800) 478-2591 or Varta Ni-MH rechargeables.

Antennas have broken since the first automated car wash. A pastor having a ‘bad sermon day’ will inevitably wrap the mic wire and antenna around the bodypack in a tight pattern, putting strain on the internal cabling. Drama personnel have a tendency to stretch the wires beyond their preset length, again causing cable breakage. Teaching every user to gently loop the cabling is a noble, but often unattainable goal.

Instead, technicians should take the responsibility to place the bodypacks on the users or have the user agree to effect needed repairs. Transmitting and receiving antennas should be in direct sight of each other and their separating distance should be minimized. This may necessitate the placement of receivers near the stage and signal be sent to the console via the snake. If the mic cable doubles as the transmitting antenna, a spare should be purchased to prepare for the inevitable transmitting antenna short.

Soldering a wireless mic system transmitter connector is the surest way of testing Christian faith. For a repair to be effective, minute cables must be placed into incredibly small openings and held in place by three molecules of solder- a good training exercise for brain surgeons! The small, exposed pins require careful alignment when attaching mics to the bodypack. Many manufacturers use the Switchcraft TA4F connector, but each brand has its unique pinout configuration, so be certain to check first.

The proprietary connectors used by Audio-Technica and Samson are well made, but extremely difficult to solder. The least expensive systems may contain a non-detachable point of entry and are best left to the manufacturer’s service department. The typical lapel package system includes the brand’s lowest quality mic as standard issue. Adding a higher quality mic from the same manufacturer will improve the sound dramatically and provide a spare element in the event of a cable failure. Receiver antennas typically use BNC connectors that can be easily cross-threaded. The proper antenna length is necessary to achieve the best reception, so a broken antenna should be replaced immediately.

In conclusion, treating wireless mic properly will reduce system downtime and frustration for the user and technician alike. Using fresh, pro-grade batteries is a better bet than a battery tester. (especially better than the tongue method) Carefully placing antennas in direct line-of-sight, and keeping their lengths correct will ensure the best possible reception. Learning to micro-solder bodypack connectors is a useful endeavor, for it will be tested at the worst possible moment. A spare mic element will prevent technician panic during services and can be used for less critical applications when necessary. Remember, always go “BAC to basics” whenever wireless troubles arise. In the next issue, we will explore the mysterious art of body mic placement.

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