AKG Acoustics WMS 40 - Manual (Page 8)

The case for wireless mics
The popularity of wireless systems is gro-
wing continuously, and they are no longer
found only at open-air events, in theaters,
and conference centers. The increasing sel-
ection of small portable wireless systems is
the key to virtually unrestricted wireless free-
dom even for amateur musicians and low-
budget users, opening up a huge diversity of
applications.
The decisive factors behind the dramatic
success of wireless systems are the easy
handling and reliable, interference-free ope-
ration now offered by most of the medium-
price wireless systems available on the mar-
ket today. In practice, however, wireless
technology is often unreasonably put down
when minimal technical conditions are not
met, usually by people who do not know any
better.
The following section examines the princi-
ples of trouble-free wireless transmission and
gives an insight into what is technically pos-
sible, and how to achieve the best results.
Just like a radio set
At first it may sound simplistic to maintain
that the operation of a wireless system is
almost as simple as that of a radio set.
However, in practice closer inspection shows
that this comparison is entirely appropriate.
Everybody knows that the reception quality of
radio signals depends not only on the locati-
on of the receiver, but also on the quality of
the transmitter, i.e. whether or not you are
inside a building, and which transmission
frequency is selected (FM 100.4, for
instance). If the reception is poor, the first
thing we do is to try and change the position
of the receiver (the radio set). Then we try to
change the position of the antenna, and if
none of these remedies helps, we try to recei-
ve the desired radio station on another fre-
quency (FM 94.7, for instance). This is a per-
fectly normal procedure, and no one would
think of calling a radio set defective or unre-
liable, simply because each of us can opera-
te a radio with our eyes shut.
Since reasonably priced, high-quality wire-
less microphone systems have only been
available to the general public for a few
years, it will probably take a while for people
to become as familiar with this new techno-
logy. However, the comparison with a radio
set is particularly appropriate and helpful for
the technically uninitiated, since most peo-
ple are able to operate radio sets correctly
thanks to their intuition and experience.
Radio waves instead of cables!
With wireless technology, radio waves are
used instead of a microphone cable to trans-
mit a signal. For this purpose, we need a
transmitter that transforms the audio input
signal (voice, instrument, etc.) into a UHF or
VHF signal and broadcasts it just like a
miniature FM radio station. The receiver then
transforms this high-frequency UHF or VHF
signal back into an audio signal and ampli-
Transmitter/receiver
The situation with a transmitter and a receiver can be com-
pared to the transmission of a signal between a radio stati-
on and a radio set. When we encounter problems with recep-
tion, we will either reposition the antenna, or look for the sta-
tion on another frequency. The principles are exactly the
same when it comes to a wireless microphone system. One of
the most important rules is that you can only receive one sta-
tion at a time with a radio, never several simultaneously.
Reflection and scattering
Every wave has certain physical properties, and this also applies in the case of wireless transmission. When a wave travels from
one medium to another, part of it is reflected and another part of it absorbed. Propagation of the absorbed part of the wave in
the denser medium is considerably reduced, whilst the reflected part is returned at the same angle as the angle of incidence
(diagram on left).
When a wave meets an irregular surface, it is not reflected uniformly and linearly, but is scattered in several partial waves, each
deflected by a differing amount (diagram on right). The energy level of the wave naturally declines every time it is reflected,
absorbed or scattered.
Shadowing
When a wave passes close to an obstacle, it is deflected slight-
ly from its linear path. Thus a number of small obstacles in a
room, such as wire screens, etc., can result in shadowing los-
ses although visually they appear transparent.
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HOW WIRELESS TECHNOLOGY WORKS
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AKG WMS BASICS