Studio Set Up

Free Radio - Basic FM Transmitter Config 09

CD players and tape decks can be your average higher 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 six 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 fairly good quality vocal types. They can be either directional or omnidirectional. 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 if this is the case. 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 cueing 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 over modulated 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, as 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 two-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.

Final Word

Although it seems like there is a lot to deal with in setting up a micro power station, it can be broken down into three areas - studio, transmitter and antenna. It should not be difficult to find someone with studio set-up experience to help with the project. Transmitters, particularly their construction and tuning, should be left to an experienced person. If such a person is not available there are a number of people who will assemble, test and tune your transmitter for whatever fee they have set. Stick to a commercial, easy to tune antenna such as the Comet if your skills are minimal. These can be purchased pre-tuned for an additional fee from FRB and L. D. Brewer. It is best to put most of the energy into organizing and setting up the station. Experience has shown that once the technical operation is in place and running, it will require very little in the way of intervention except for routine maintenance (cleaning tape heads, dusting, etc.) and occasional replacement of a tape or CD player.

What requires most attention and "maintenance" is the human element, however. More time will be spent on this than any equipment. As a survival strategy it is best to involve as much of the community as possible in the radio station. The more diverse and greater number of voices the better. It is much easier for the FCC to shut down a "one man band" operation than something serving an entire community. Our focus is on empowering communities with their own collective voice, not creating vanity stations. Why imitate commercial Radio?

Before you commit to your first broadcast, it would be advisable to have an attorney available who is sympathetic to the cause. Even though they may not be familiar with this aspect of the law there is a legal web site, which offers all of the material, used in the Free Radio Berkeley case. There are enough briefs and other materials available to bring an attorney up to speed. That web address is: www.surf.com/-graham.

A list server, [email protected], for the National Lawyers Guild Committee on Democratic Communications puts you in touch with the group that is doing a lot of the legal work on micropower broadcasting. Their contact address and phone are:

National Lawyers Guild Committee on Democratic Communications
368 Hayes Street (between Franklin and Gough)
San Francisco, CA 94102
(415) 575-3220
Fax (415) 575-3230

TO BE CONTINUED >> The following is a guide to what to do when the FCC (in RSA ICASA?) knocks.