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Microphones: Care & Feeding of the Wireless Variety

Today’s wireless microphones are quite different from the early wireless microphones. At first, wireless microphones used to be very temperamental and expensive; now they’re reliable and affordable. However, if you expect to get a long and trouble-free life from your wireless microphone, you must still take care of it. The four basic things to watch are: the batteries, the lavalier microphone and its cable, frequency selection, and antenna location.

Batteries are extremely important for reliable operation (Figure 1). If the battery voltage is too low, the wireless system is much more susceptible to interference. The interference will show itself in pops, fizzes, distortions, or other strange noises.

The key is to have batteries that are fresh. However, buying a new battery doesn’t always guarantee it’s good. Always check your battery with a battery tester if you don’t want any nasty surprises. For long battery life, use an alkaline-type battery. The new lithium types can even give much longer life.

If you want the convenience of rechargeable batteries, there are now several types to choose from. The standard rechargeable was the Ni-Cad. The new-kid-on-the-block is the nickel metal hydrid or Ni-MH.

One thing to look for in a Ni-Cad battery is to be sure it has the proper voltage output. If your wireless microphone uses nine volt batteries, it is naturally designed to use a voltage that is close to nine volts. However, many Ni-Cad batteries that are labeled nine volts are actually only 7.2 volts (six cell). This is not adequate voltage for long, interference-free life. You must use an 8.4 volt (seven cell) Ni-Cad battery.

Ni-Cad batteries also can develop a condition called Ni-Cad memory (See Figure 2) This occurs when the battery is only discharged to the same point (B) each time and then charged back up (A). After a while, the Ni-Cad battery won’t give any more life past point B than it was conditioned to provide. The best way to prevent this memory is to occasionally discharge the battery to point C. This could be done after about 20-30 short discharges. A better rechargeable battery is the Ni-MH. The Ni-MH will give longer life and does not have the memory problems.

Note: It is not wise to discharge the rechargeable battery to a dead state. This may permanently damage the battery.

Next to bad batteries, the cable on the lavalier (neck) microphone is often a source of problems. There are several things you can do to ensure a long cable life. First, minimize the flexing of the cable. The wires in the thin miniature cable are very small (Figure 3). They will break if flexed enough. Also, try to keep the cable from severe kinks or bends.

If the cable is wrapped tightly around the transmitter case, the cable will have a severe bend at the connector or where the cable comes out of the transmitter case. The cable will eventually break down if it is continually bent at one point. Also, don’t pull on the cable or dangle the transmitter from the cable. (These hints also apply to the antenna if your transmitter has a separate antenna wire)

The microphone is also a potential source of problems. It can lose its life if it is dropped onto a hard floor or counter top when it is being put away. Remember, it can be damaged if it is not treated properly.

Frequency selection is also a critical factor in providing reliable operation. As wireless microphones become more and more common, this problem continues to increase.

Each wireless microphone system must be on its own separate channel or frequency. If another system is on the same channel, interference can or will occur. When you purchase a wireless microphone, try to check out area churches, schools, or other possible users. Find out what frequencies their wireless microphones are operating on. Then select a channel that won’t interfere with those other microphones.

If you’re using multiple wireless microphones in your school, you must select channels that are compatible with each other. Just having different frequencies is not the total answer. Many other factors must be considered, especially if you have systems from several different manufacturers.

Lastly, antenna location is critical for proper operation of the wireless microphone system. The antenna(s) must receive the strongest possible signal at all times, or noise/pops may occur.

First, the antenna on the transmitter must not be coiled up, it should be straight (Figure 4). Next, be sure the antenna(s) on the receiver are not placed next to metal. Be aware of any metal in walls, window frames, cabinets or racks.

Consult your system’s manual for the manufacturer’s recommendations on antenna orientation and positions. If you need to remote the antenna, be aware of the maximum length and proper type of coax cable.

Paying attention to these details and taking proper care of your wireless microphone(s) will result in long life and trouble-free operation.

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