Author:
Jason Struble WorldMusicSupply.com
So you want to buy or
use a wireless…
Here is everything you
need to know about them to be an educated user / consumer.
1 Transmitter
All wireless
transmissions start with a transmitter. The transmitter is the device that
broadcasts the signal via RF (Radio Frequency) waves to the receiver. They can
be in the form of a body pack transmitter with lapel or headset microphone, or
an instrument cable. It also can be built into a handheld microphone. Better
quality body pack systems feature a disconnect point between the body pack and
its microphone. In less expensive units the microphone or cable is often
permanently attached to the transmitter. In the event of a short in the cable,
the entire receiver must be serviced rather than simply replacing the removable
cord or microphone.
Any good quality
transmitter should have an on-off /standby switch. This allows you to turn the
unit on or off from the transmitter, or mute it temporarily. This mute (standby)
is beneficial should you get a burst of feedback and you’re not near the sound
system. The standby feature is also beneficial when you need to talk to someone
without being broadcast through the sound system.
In a handheld
microphone system, the quality of the microphone element is also a determining
factor in the overall sound quality. In handheld systems, the microphone
element is fixed to the transmitter and often cannot be easily interchanged.
One benefit of body pack systems, is that you can often choose what quality or
type of microphone you want, or can easily upgrade at a later point. You can
start with a lapel microphone, then later purchase a headset, clip on
instrument, or specialty microphone. Even a special guitar cord or microphone
cable can be added to your body pack. All these components can be interchanged
to make your body pack wireless system very versatile with multiple microphone
or input types.
2) Receiver (often
referred to as base unit)
The receiver plays the
biggest role in determining the quality of a wireless system. The better the
receiver, the better the unit will operate. After all, a broadcast signal is
only as good as the unit that converts the airwaves bouncing around back into an
audio signal to feed your sound system.
A Lesson on Receivers
& Diversity?
Diversity is a term
that is often used very loosely and incorrectly. Often you will see systems
advertised as being true diversity when in fact they are not. Before getting
into the differences, a brief explanation of how a receiver works is due.
Consider a wireless
receiver to be like a radio that is preset to only receive one station and no
other. It receives the signal via its antenna, converts it back to the original
audio signal. This signal is then sent to the sound system for amplification.
An often-asked question is… “Can I get two packs / mics and use them both on one
receiver?” The answer is NO; you cannot receive multiple signals on the same
receiver frequency. It would be like two songs broadcasting simultaneously on
the same radio station. Here is another way to look at it. It’s happened to us
all; just when you start grooving to a great song while driving in your car,
another song you can’t stand starts creeping into your personal jam session.
Within 30 seconds or so your radio is jumping between the two songs and you find
yourself reaching for the dial in frustration. Wireless mics work the same way.
There
are systems that come with multiple mics and a single receiver. This situation
is where there are multiple receivers built into one “box”. They are still
separate receivers. Typically these are entry-level units in an attempt to make
multiple wireless affordable, often (but not always) at the expense of quality.
Many manufacturers offer systems with both a body pack and a handheld. Most of
the time you can use one or the other, but not both simultaneously.
Non-diversity (often
mistakenly called single diversity)
is simple to explain. There is no diversity at all. You have one antenna and
that’s it. When the signal fades, is interfered with, drops out, or becomes weak
you may get bursts of static or unwanted noise. There is nothing the system can
do when this occurs. Grin and bear it, and hope it goes away fast. There are
better and worse quality levels of non-diversity systems. Any good
non-diversity system should have one of two things either two antennas (one of
which is a ground antenna) or an all-metal case (see Grounding below). The
second antenna is a ground antenna. They are not rabbit ears.
Di-Pole Diversity
in my opinion is NOT
Diversity, but rather creative marketing jargon. By definition it is when you
have two antennas that feed a single receiver circuit. I say Di-Pole means two
sticks. You have two antennas which does increase the quality ever so slightly
but only by the degree of separation in physical distance and the odds of one
being stronger in reception than the other. There is still no true backup on
itself. They often look like a true diversity system and far too often are
mistakenly or falsely advertised as such. Since the receiver does all the work,
and there still is only
one receiver and no backup
on it, the reliability does improve, but only minimally in my experience.
True Diversity
is when the receiver has 100% redundancy in itself. There are two antennas,
each has its own independent receiver circuit. This is all built into one
chassis. The signal enters both antennas independently to its receiver. The
signal of each receiver is tested roughly 600 times per second to see which
signal is best. This allows seamless transition back and forth between the
receivers. The testing circuit can vary in quality between brands and models
and make a big difference as well. Some models test the signal strength and
that’s it, while some systems add a second test for audio signal quality and
compare the two results for even greater reliability. True diversity is by far
the most reliable type of receiver.
Keep in mind that NO
wireless system is foolproof. Every wireless system is subject to interference
at some time, no matter how much you spend. The reason is that airwaves are
simply unpredictable. There are unregulated broadcasts, illegal CB & radio
boosters, solar flares, electrostatic energy, and other mysterious forces at
work that sound engineers refer to as “ghosts.”
