Many people have initiated or are advocating technical training programmes
for community radio. The starting point for many of these programmes is to
teach basic electronics. This is not the approach of this manual.
We believe that the most important thing is basic operational training. Many
people are able to make good tea or coffee, but most of us don’t understand the
resistive element that heats the water.
The same applies to the community radio studio. You can make good
programmes by using broadcast equipment efficiently and creatively, but you
don’t have to understand the complex integrated circuits and resistors inside
the mixing consoles.
An understanding of what the equipment does and how
to use it, and the confidence to experiment, is really all you need to start
producing good quality sound.
The machines in a radio station rely on people to operate them, and so they can
only be as good as the station’s staff and volunteers. A community radio station
is a complex environment, with many departments, all depending on each other.
To make good radio, every department needs to focus on its individual task,
while never losing sight of the station’s overall mission.
The technical department is no exception. The station depends on the technical
department to keep broadcasting sound. At the same time, if the technical
department is to succeed in keeping the equipment working, there must be
good governance and management, and all staff and volunteers must be
committed to the mission of the station.
The National Community Radio Forum (NCRF) and Open Society Foundation
for South Africa (OSF-SA) have developed this manual as a resource to help
community radio staff and volunteers. It can be used as a reference for
technicians as they go about their day-to-day work, cleaning the studios and
doing repairs. It can be used to train new people in the programming department
- the many producers, newsreaders, presenters and DJs who will operate the
studios. It can be used if you need ideas about how to develop your studios
further, especially in relation to new digital technologies. We’ve included prices
and costs so that the manager can use the manual to budget for repairs and
replacements.
The manual also aims to demystify studio equipment - to help you understand
how to use your studios properly and to give you the confidence to experiment.
We hope to expand your technical knowledge and vocabulary and - who knows?
We might even attract some readers to want to learn more and take up a future
in electronics.
The manual provides information about:
• The broadcast system
• Studios at a radio station, and how to link them
• The types of equipment you are likely to find in a community station
• What the equipment in the studios can do
• Commonly used technical language and concepts
• Basic maintenance, fault-finding and problem solving.
The broadcast system
Broadcasting is the distribution – or transmission – of sounds and / or pictures
using electrical signals, so that they can be heard and seen over a large area. We call
the combination of equipment used to make broadcasting happen a broadcast system.
The first task of a radio broadcast system is to change sound into electrical energy.
This electrical energy is called an audio signal. We change sound into electrical
audio signals because these signals can be changed in almost unlimited ways
by using electronic equipment. In audio electronics, pieces of equipment that
change energy from one form to another are called transducers.
The second job of a radio broadcast system is to process or change audio signals
so that we can broadcast them. Pieces of equipment that change one or more
aspects of an audio signal are called signal processors.
An input transducer (most often a microphone) changes the sound of a voice
into a varying electrical signal, a voltage or current that is an exact representation
of the sound. This varying voltage or current is called an audio signal.
The microphone is not the only piece of equipment in the broadcast system
that produces audio signals. There are many other pieces of equipment, such
as compact disc players, minidisc players, tape decks and turntables in the
broadcast system, all of which produce audio signals. We call them source
equipment. We use signal processors to change one or more characteristics of
the audio signals produced by the source equipment..
One of the most common purposes of a signal processor is to change the size
of a signal. Most often the signal is made “bigger”. This is called amplifying a
signal. Once the amplified signal is converted back into sound, it is much
louder than before.
In the diagram of a radio broadcast system on the previous page, the block
marked signal processing represents several pieces of equipment, such as preamplifiers, mixers, power amplifiers, effects units and so on.
In the diagram, the block marked transmission represents the transmitters,
antennas and so on that produce the radio signal that your radio set – or receiver
– picks up. The processed audio signal is carried to your radio as a radio signal.
The process of joining the audio signal and the radio signal is called modulation.
This is the origin of the abbreviations FM and AM, which stand for frequency
modulation and amplitude modulation.
Your radio, or receiver, receives the radio signals, which have been broadcast
by the transmission equipment. The receiver works in the opposite way to the
transmission equipment. It turns the radio signal back into an audio signal by
demodulation.
The radio set sends the audio signal to an output transducer - loudspeakers or
headphones. These output transducers work in the opposite way to the input
transducers (microphone and other source equipment) at the start of the system.
The output transducers convert electrical audio signals back into sound that
we can hear.
The radio station’s technical responsibility is to produce a good quality radio
signal that listeners can pick up with their receivers. This means delivering the
best possible quality audio signal to the transmission block, and ensuring that
the transmission block converts it into a radio signal of good enough quality to
reach radio receivers in the community.