Radio Station

Radio Station

A radio station is a set of equipment necessary to carry on communication via radio waves. Generally, it is a receiver or transmitter, an antenna, and some smaller additional equipment necessary to operate them. Radio stations play a vital role in communication technology as they are heavily relied on to transfer data and information across the world.
More broadly, the definition of a radio station includes the aforementioned equipment and a building in which it is installed. Such a station may include several “radio stations” defined above (i.e. several sets of receivers or transmitters installed in one building but functioning independently, and several antennas installed on a field next to the building). This definition of a radio station is more often referred to as a transmitter site, transmitter station, transmission facility or transmitting station. An example of this definition is Bethany Relay Station of the Voice of America which had seven broadcast transmitters and could broadcast up to seven independent programs (even produced by different broadcasters) simultaneously, as well as several communications transmitters and receivers.

Transmission Equipment

Audio processor
The audio processor ensures that the amplitude of the audio signal does not exceed a certain limit. Without a processor the signal can become overmodulated, which decreases the quality of the resulting radio signal and can cause splatter on other frequencies.
The transmitter modulates the audio signal, turning it from a sound wave that our ears can hear into a radio wave that FM receivers can detect. It is a requirement that the FM transmitter for your LPFM station is \type certied” – meaning it has been through certain tests by the manufacturer. It may be necessary to call and ask the transmitter maker if their transmitterst the bill. An important transmitter characteristic is output power, which determines how strong the signal is and therefore how far it reaches. You will likely need something in the 100 watt to 200 watt range, but the needs of every station will be di
erent. See the \ERP? TPO? Gain? English please…” section in the Notes for more information about output power.
The antenna radiates the modulated signal. Some antennas radiate equally in all directions, while others are focused in a particular direction. LPFM stations are limited to an omnidirectional pattern. There are dierent polarizations for antennas – we recommend a circularly polarized (CP) antenna – one which radiates equally in the horizontal and vertical planes. You will need twice the transmitter power for a CP antenna, but it’s worth it.
Tower or mast
The location of an antenna (particularly the height) will impact how far the signal travels. FM waves travel best within the line of sight of the antenna. If you have an antenna site that is already high, such as a hill or a tall building or church steeple, you can probably mount the antenna on a simple pole or mast. If not, you may be able to build a dedicated tower structure for the antenna. For more suggestions regarding towers and masts, read \Hang ‘Em High: Options for antennas, masts, and towers,” available on our website.
Grounding and lightning protection
An antenna structure should be connected to an electrical ground. This will allow charges to drain from the structure to ground, preventing a charge build-up. A strong path to ground will also help to reduce the damage to equipment if lightning strikes.
Cables and connectors
Coaxial cable is used to carry radio frequency signals. Types of coaxial cable vary in the amount of attenuation, or signal loss over a certain length. It is most 3 important to use low-attenuation cable for long lengths, while it may be acceptable to use slightly higher attenuation cable over short distances. You will need to match the connectors on the cable to the output of your transmitter and the input of your antenna.

Studio-to-transmitter link
The studio transmitter link (STL) carries the audio signal from the studio site to the transmitter (and antenna) site. If your studio is close to your transmitter – for instance, if the studio is in a building and the transmitter and antenna are on the roof – you may be able use a long audio cable. If the transmitter location is further from the studio, options include microwave transmitter systems with directional dishes, a \dry pair” (unused telephone line) provided by a phone company, unlicensed wireless internet or streaming over the public internet. More specics on these options are detailed in \Sound Around Town: Some options for linking your studio to your remote transmitter site,” available on our website.


December 20th, 2017

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