Page 107 - DCAP311_DCAP607_WIRELESS_NETWORKS

Unit 6: Wireless PAN Systems

z z Avoidance of cabling problems common with wired microphones, caused by Notes
constant moving and stressing the cables.
z z Reduction of cable "trip hazards" in the performance space
The disadvantages are:

z z Sometimes limited range (a wired balanced XLR microphone can run up to 300 ft
or 100 meters). Some wireless systems have a shorter range, while more expensive
models can exceed that distance.

z z Possible interference with or, more often, from other radio equipment or other radio
microphones, though models with many frequency-synthesized switch-selectable
channels are now plentiful and cost effective.

z z Operation time is limited relative to battery life; it is shorter than a normal condenser
microphone due to greater drain on batteries from transmitting circuitry, and from
circuitry giving extra features, if present.

z z Noise or dead spots (places where it doesn't work, especially in non-diversity
systems)

z z Limited number of operating microphones at the same time and place, due to the
limited number of radio channels (frequencies).
Techniques
The professional models transmit in VHF or UHF radio frequency and have 'true' diversity
reception (two separate receiver modules each with its own antenna), which eliminates
dead spots (caused by phase cancellation) and the effects caused by the reflection of the
radio waves on walls and surfaces in general. (See antenna diversity).
Another technique used to improve the sound quality (actually, to improve the dynamic
range), is companding. Nady Systems, Inc. was the first to offer this technology in wireless
microphones in 1976, which was based on the patent obtained by company founder John
Nady.
Some models have adjustable gain on the microphone itself, to be able to accommodate
different level sources, such as loud instruments or quiet voices. Adjustable gain helps to
avoid clipping.
Some models have adjustable squelch, which silences the output when the receiver does
not get a strong or quality signal from the microphone, instead of reproducing noise. When
squelch is adjusted, the threshold of the signal quality or level is adjusted.
Products
The original manufacturer of the wireless microphone was Vega Electronics Corporation.
AKG Acoustics, Audio Ltd, Audio-Technica, Electro-Voice, Lectrosonics, MIPRO, Nady
Systems, Inc, Samson Technologies, Sennheiser, Shure, Sony and Zaxcom are all major
manufacturers of wireless microphone systems. They have made significant advances
in dealing with many of the disadvantages listed above. For example, while there is a
limited band in which the microphones may operate, several high-end systems can consist
of over 100 different microphones operating simultaneously. However, the ability to
have more microphones operating at the same time increases the cost due to component
specifications, design and construction. That is one reason for such large price differences
between different series of wireless systems.
Generally there are three wireless microphone types: handheld, plug-in and bodypack:
Handheld looks like a 'normal' wired microphone, but may have a bigger body to
accommodate the transmitter and battery pack.
Contd...

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