Idiot’s guide to audio equipment for broadcasting
Every radio station needs a source of audio material to broadcast. Unless you’ll just be re-transmitting signal from another radio station you will need a source of this audio material. Here are basically two typical setups that can help you setup your own broadcasting studio.
Today almost any station will have at least part of studio based on computer. A huge digital audio library is usually stored on a disk of studio computer. There are also many specialised computer programs available for the purpose of organising and scheduling audio material.
At the beginning you can start with free programs such as Winamp, which is not specialised for this purpose but does a pretty good job (the pic is below) since it can play most sound formats, including MP3 and others. Many plugins exist, making it possible to even schedule music and perform all kinds of processing and functions perfect for radio stations.
Winamp supports various plug-ins. Plug-in is an add-on to a program that you can use to add functionality. Audio-stocker is one of the better ones. It seems to be perfectly suited for broadcasting. It provides FM-station-like compression, at no additional cost (provided you own a PC and a sound card).
A PC with sound card and suitable software CAN actually take care of most of your audio processing needs, at least in the beginning. As your station grows you eventually need to purchase DSP stereo processor/limiter.
Some professional DJ’s hate using computerised audio systems. They say that PC’s can let them down, we all know the good old blue screens that Windows produces now and than and a crash in the middle of a hot show can take you offline for a couple minutes at best, a disaster.
Beginner would probably start by plugging his CD or cassette deck directly into his transmitters audio input. However this is not a proper way of doing things. Classical setup would be something like this:
1. Audio Low pass filters
Audio signal has to pass low pass filter before it goes into stereo encoder. Audio signal should not appear close to or above 19KHz as this is where stereo PILOT is and it would cause the Stereo LED on the receiver to flicker as well as receiver shifting to MONO mode. Even if you transmit in MONO, such low pass filter should be used. Why? To limit space that your signal uses on the band. Your signal could become wider than the standard deviation for FM broadcasting, resulting in interference to other radio stations. Interference means you can be fined! Standard calls for all audio above 15KHz to roll off quickly. Our stereo encoders have low pass filter inside.
2. Audio limiter
Makes sure your signal never gets too far from center frequency. A maximum deviation of 75KHz should never be exceeded since that means interference to adjacent channels and audible distortion in receivers. Our stereo encoders have a limiter inside.
Increases your average loudness while not exceeding maximum allowable deviation. Pushing this too far will make you sound distorted. The general trend nowadays is to push compression above all reasonable limits. Our DSP stereo encoders have compressor inside.
4. Stereo encoder
Stereo DSP processors for broadcasting have stereo encoder already inside. Many FM transmitters also have stereo encoders inside. However, if this is not the case you will have to purchase one. Choose wisely when you’re shopping for stereo encoder and most of the above requirements can be yours in a single device. Our DSP stereo encoders perform all of the requirements without breaking your budget.
A mixer is pretty much a must. And D&R AirMate or D&R Webstation really shine here. Pushing real sliders beats will never be the same as clicking with a mouse. Get a decent unit with USB audio and plenty of various inputs.
6. FM/AM/SAT/SW tuner, CD players, turntable…
A tuner can be used to re-broadcast signal from another station, CD players and turntables may be needed from time to time
A microphone, of course, is a must. At least one, possibly several.
Good set of headphones for speaker and technician at the mixer. With some spares.
8. Audio isolated studio
Isolated from external world (traffic), with a 2-3 layer window towards technician at the mixer. With quiet air conditioner, monitor speakers and headphones.
9. Telephone hybrids
Have your listeners call in and reporters report from the field. Telephone hybrids can nowadays be old-school analog, IP phone or wireless GSM types.
Balanced audio inputs almost always make a big improvement. Balanced audio inputs help eliminate noise generated by ground loops or strong RF fields. A hum experienced with unbalanced audio wiring usually disappears or at least reduces as soon as proper balanced cabling is used. Check our stereo encoders, they all feature balanced inputs.
Digital inputs are another great way of handling noise. AES/EBU is a de-facto standard for digital audio in FM transmitters. Some of our transmitters also have USB audio inputs. Here a transmitter will appear as a sound card to your computer.
NOTE: Always keep your aerial away from your audio circuitry and audio cables, power supply and even transmitter. If you cannot meet these requirements, you could experience feedback and other RF problems. Strong RF field can make CD players and other digital devices go bezerk.
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