A typical broadcast studio consists of an audio mixer (DJ style works best), one or more CD players, one or more cassette tape decks, a turntable or two, several microphones, and a compressor/limiter. Optional items can include a cart machine and a phone patch. Reasonable quality mixers start at $200 and go up in price from there. DJ styles are best since they have a large number of inputs available and support turntables without the need of external phono preamps. Any mixer you select should have least two or more microphone input channels. These should be low impedance inputs. Other features to look for include high visibility VU (level) meters, slide faders for each channel, switchable inputs for each channel, stereo or mono selection for the output signal, and at least one or more auxiliary outputs for an air check tape deck and studio monitors. Behringer is one manufacturer of good quality mixers and other audio equipment. Their DJ1000 mixer is a good choice, costing less than $200. CD players and tape decks can be your average high quality consumer audio gear. Day in and day out usage will eventually take their toll so pay for the extra warranty period when it is offered. When one wears out in 6 months or so, just take it back under warranty for either repair or replacement. DJ style turntables are the best choice for playing vinyl. Cheaper units just will not stand up to the wear and tear of daily usage. Select a heavy-duty stylus as well.
Microphones should be good quality vocal types. They can be either
directional or omni-directional. Directional microphones will pick
up less ambient noise but need to be on axis with the
person’s mouth for best pick up. Since some folks do not pay
attention to where the microphone is in relation to their mouth, an
omnidirectional might be considered a better choice. A distance of
about four inches should be maintained between the microphone and
mouth. Place a wind screen foam piece over each microphone. Some
microphones have built-in shock and vibration isolation to keep
bumps to the microphone from being audible. It is a good idea to
use some sort of isolated holder for the DJ microphone. An old
swing arm lamp can be adapted to hold a microphone.
For programmers who do a lot of reading of material on the air, a
headphone microphone is something to consider since it will
maintain a uniform distance from mouth to microphone no matter
where the head moves to. One drawback is that they tend to be a bit
fragile in rough hands.
Headphones are essential for monitoring and curing up program
material. You can either opt for high quality rugged units that are
a bit costly or plan on replacing an inexpensive set every few
months.
A limiter/compressor is an essential part of the audio chain. It is
used to keep the audio signal from exceeding a preset level.
Without this the transmitter will be overmodulated, resulting in
signal splatter and distortion. Signal splatter will cause
interference with adjacent stations and distortion will send your
listeners elsewhere.
Common to most limiter/compressors are a set of controls - input
level, output level, ratio, threshold, attack and decay. To
properly set up the mixer, limiter/compressor and transmitter, you
start with a steady audio source (a signal generator plugged into
the board or a test tone CD, tape or record). You adjust the input
level and master output level controls so that the meters are
reading zero dB. Master level should be at mid position. Audio
output goes from the mixer to the limiter/compressor and from there
to the transmitter. Do not turn the transmitter on at this
time.
Most limiter/compressors have indicator lights or meters to show
how much gain reduction is being applied and the output level. Set
the ratio control to the infinity setting; this enables hard limit
function. Attack and decay can be set around mid position. Adjust
the threshold and the input level until the gain reduction shows
activity. Adjust the output level so that the indicator lights or
meters show a 0 dB output level.
Turn the level input on the transmitter all the way down and power
up the transmitter. Monitor the signal on good quality radio.
Slowly turn the level control until you can hear the test tone.
Compare the signal level to that of other stations. Your level
should be slightly less since most other operations are using quite
a bit of audio processing on their signal. You may have to make
fine adjustments to the limiter/compressor to get things exactly
right.
When everything is set up correctly, any audio signals that exceed
0 dB on the board will be kept at that level by the
compressor/limiter. You will need to listen carefully to the signal
to make sure when a “hot” audio source exceeds this,
that the transmitted signal keeps an even level and does not
distort or splatter. There will be some interplay between the
output level and the threshold setting. Nor do you want a signal
that is too low in level either since that will produce a weak
sounding broadcast.
A very important consideration is to keep as much distance between
the studio gear and the transmitter as possible. RF (radio
frequency signals) will find their way into audio equipment and
produce a hum or other types of noise. You can separate the two
areas by using a low impedance cable between the limiter/compressor
and the transmitter. This can be a long microphone cable with XLR
connectors or a made up shielded 2 conductor cable with XLR
connectors. You can have about 150 feet of cable, maximum. A high
impedance to low impedance transformer will be needed at one end or
both depending on whether the limiter/compressor and transmitter
have low or high impedance connections. These transformers usually
have an XLR female connector on the low impedance side and a
1/4” phone plug on the high impedance side. If your
transmitter has an RCA style input, you will need the proper
adapter to go from 1/4” phone plug to RCA plug.
Your studio should be arranged to provide easy access to all
controls and equipment with plenty of table space. An L or
horseshoe shape works well for the studio bench. An open area
within the sight line of the operator should be provided so there
will be a place for extra microphones and
guests.