- Quote: "There is
nothing in the world worse than a cheap wireless system," Hosch
says. "It's scary when your future is hanging on a $ 1.98
battery. Anytime you can, you should get someone to use a wired mic
over a wireless system." Scheirman adds, "and just remember
that even the best wireless microphone system, a $10,000 system, is
almost as good as a mic cable." (From TCI,
May 1993, page 25).
A wireless microphone system
is a small-scale version of a typical commercial FM broadcasting
system. In a commercial broadcasting system, a radio announcer speaks
into a microphone that is connected to a high-power transmitter in a
fixed location. The transmitted voice is picked up by an FM receiver
and heard through a speaker or headset.
In a wireless microphone
system, the components are miniaturized but the same principles
apply. The transmitter is small enough to fit into the microphone
handle or into a small pocket-sized case. Since the microphone and
transmitter are battery powered, the user is free to move around
while speaking or singing into the mic. The transmitted voice is
picked up by a receiver that is wired to a speaker.
Two types of microphones are
available with wireless mic systems: the handheld mic, with a
transmitter in its handle; and the lavalier mic, which is small
enough to be concealed as a lapel pin or hung around the neck.
Lavalier mics are wired to miniature body-pack transmitters, which
fit into a pocket or clip onto a belt. There is also a transmitter,
designed by Lectrosonics, which accepts any three-pin XLR input and
acts as a wireless mic-- then you can use any mic you want with the transmitter.
Wireless microphones are
widely used today in television and video production. They eliminate
the need for stage personnel to feed cables around cameras, props,
etc. For location film production, as well as ENG (Electronic News
Gathering) and EFP (Electronic Field Production), wireless mics make
it possible to obtain usable first take sound tracks in situations
that previously required post-production dialogue looping. The cost
saving can be significant.
Handheld mics are used by
performers on camera where they provide the freedom needed to move
around the stage and gesture spontaneously. They are used by speakers
and entertainers who need to pass the mic from one person to another.
In concerts, hand-held wireless mics permit vocalists to walk and
dance around the stage and even into the audience without restriction
and with no chance of shock in the event of rain.
Lavalier mics are used in
game shows, soap operas and dance routines. They eliminate the need
for boom mics and help to alleviate visual clutter. Lavalier mics are
used by MCs, panelists, lecturers, clergy, stage actors, and dancers
because they can be concealed easily and provide hands-free mobility.
Some lavalier transmitter models have high impedance line inputs that
accept cords to create wireless electric guitars.
Technology in the early 1970s
introduced the integrated circuit compandor which was incorporated
into wireless mics to reduce noise. At about the same time, the FCC
authorized the use of frequencies in TV channels 7-13 for wireless
mics. Thus the wireless microphone's most serious problem, radio
interference from other services, was virtually eliminated. Later,
the application of diversity reception minimized the problem of
dropouts (transmission losses due to cancellation of radio waves),
greatly improving system reliability.
Today's wireless mics perform
almost as well as conventional wired mics. In the 1980s, wireless
mics were manufactured with an improved dynamic range and smaller
transmitters, a result of better compandor integrated circuitry and
advanced circuit design techniques. A variety of standard microphones
with different sound characteristics is available.
There are no international
standards for wireless mic radio frequency allocations. Performance
is not controlled for transmitter power limits, frequency stability,
or RF bandwidth occupancy. Wireless mics could therefore,
theoretically, operate at any frequency. Certain frequency bands are
more commonly used. In the United States, the FCC regulates the
operation of wireless mics at specified frequency bands.