Country Home Products Wireless Microphone Systems - Manual (Page 48)

Receivers for theatrical applications are not unique but
they must be of high quality to allow multiple system use with-
out interference. It is not unusual to use as many as 30
simultaneous wireless microphone systems in a professional
musical theater production. This number can only be handled
with systems operating in the UHF range. 10 to 12 systems is
the practical limit at VHF frequencies. In addition, separate
antennas and antenna distribution systems are necessary for
any installation involving a large number of systems.
Though small-scale theater applications can be done with
a moderate investment in planning and equipment, large-
scale productions usually require professional coordination of
wireless microphone systems to achieve successful results.
This becomes an absolute necessity for a touring production.
WORSHIP
Worship services
may include
presenter, vocalist
and instrument
applications. While
wireless vocal and
instrument use is
essentially the
same as outlined
in the preceding sections, the presenter function may be
somewhat different. Microphone, transmitter and receiver
selection are as before but placement of the components
may require extra consideration.
In particular, proper location of the lavaliere
microphone and/or transmitter may pose problems
because of robes or vestments. It is still necessary to
position the microphone as close as practical the user’s
mouth for best results. Different methods of attachment
may be necessary. Access to transmitter controls can also
be problematic. Use of accessory microphone mute
switches similar to those worn by sports referees can be
the answer. Though an omnidirectional type microphone
is easier to use, a unidirectional model may be chosen to
allow more gain-before-feedback. In this case pop
sensitivity and mechanical noise should be taken into
account. Again it is very important to adjust the transmitter
level for the individuals’ voice under actual conditions.
Note that headworn microphones are becoming more
acceptable for worship applications. They provide the
highest gain-before-feedback in a hands-free type.
Because most worship services involve both wired
lectern microphones and wireless lavaliere microphones it
often happens that the person wearing the wireless is also
speaking at the lectern. If the voice is picked up by both
microphones an acoustic phenomenon known as "comb
filtering" occurs which creates a hollow, unnatural sound.
The solution is to turn down one of the two microphones
whenever they are within one or two feet of each other. In
most cases it will be less noticeable to turn down the lectern
microphone when the wireless wearer approaches it.
Proper frequency selection is necessary for any
worship application. Since a fixed location is the norm, unused
TV channel frequencies are the best recommendation, not
"traveling" frequencies. The simultaneous use of other wireless
microphone systems by vocalists and musicians during the
service must be considered as well. In addition, wireless
microphone systems at other churches or facilities within 1000
feet of the site should be included in any program for
frequency coordination.
Finally, receivers should be located and adjusted
according to the suggestions made earlier. Even with
proper squelch settings, though, it is very strongly
recommended to turn off or turn down the outputs of
any receivers that do not have an active transmitter.
This will avoid noise from random RF interference
being heard in the sound system.
BINGO
Wireless microphones have become common in
large-scale bingo halls. Though the caller is typically in a fixed
location and uses a hardwired microphone, the checkers must
be able to move about the hall in order to verify the cards.
Handheld systems are the usual choice but bodypack
systems with either headworn or lavaliere microphones are
also used. Receivers are in fixed locations.
Selection and operation of wireless for this application is
straightforward though often strongly influenced by budget. In
particular, it is often requested that a single receiver be used for
multiple transmitters on the same frequency since only a
single checker need be on the air at any one time. While this
is technically possible it becomes difficult in practice for two
reasons: failure to turn off transmitters when not needed and
noise that occurs when transmitters are switched on and off.
As indicated previously, simultaneous operation of more than
one transmitter on the same frequency creates severe
interference. In addition, some amount of switching noise is
inevitable except in tone-key squelch systems.
Transmitters should be muted when not being used,
but power should remain on to eliminate possibility of noise.
If it is desired to turn the checker wireless transmitters off
during the event, make sure that squelch levels are
adjusted properly. Ideally, the corresponding receiver(s)
should be turned down until needed. Tone-key squelch
systems are useful in this application to allow transmitters
to be turned on and off without noise.
Receivers and antennas should be located properly for
coverage of the intended area. The usual suggestions
concerning frequency selection apply. In particular,
unused TV channel frequencies are recommended since
bingo systems are generally in fixed locations.
49
Selection
and Operation
of W
ireless Microphone Systems
C
H A P T E R
5
Application Notes