FM radio is a method of radio broadcast with frequency modulation, which is very similar to the sound we hear on our television. invented by American radio pioneer Edwin Armstrong, wide band FM is still used around the world to transmit high quality sound over commercial radio channels. With the advent of digital technology and better devices, FM radio can now be transmitted via USB from computer to PC. The USB transmission is as good as conventional radio stations.
A fundamental understanding of how the entire process works is essential for understanding how the new technology works. Basically, the new technology involves two types of transmitter and receivers: FM modulated signals, which are sent from one radio to another; and FM digital signals, which are received from a second radio and converted into audio. A third type of device is called a tuning fork which is used to adjust the frequency of the signal being transmitted. The tuning fork is coupled to an electronic transducer, which converts the analog signal into digital waves and the strength of these waves is measured by an analyzer.
These FM radio devices are commonly used in cars to receive satellite radio and used in public areas to aid communication among government offices and other institutions. With the advent of cheap computers and microprocessors, the efficiency of the FM transmitters and receivers can be improved greatly, which leads to a significant decrease in power consumption. This means that a larger number of stations could be reached with fewer watts consumption, thereby reducing the cost of maintaining these devices and maintaining the quality of the broadcast.
The most important improvement is found in the pre-emphasis or in short, the removal of pre-emphasis marks. Most radio stations maintain a repeating series of audio frequencies that are used to announce a specific song or other desired action. The purpose of these audio frequencies is to emphasize certain words or musical notes. A station that utilizes pre-emphasis audio frequencies would not have the capacity of announcing all words and music notes in one single song. Such type of device would not only be very annoying to listeners but it could also cause legal issues for radio stations.
The pre-emphasis time constant is employed in many radio broadcasting stations to help in reducing the amount of noise produced by the transmission. Without this function, the audio signals would begin to repeat once the next message begins to play. In order for these pre-emphasis times to remain unobtrusive, the amount of time used must be less than 1% of the entire message.
Another FM radio function that is seen in many countries is called carrier independence. This means that the carriers send their own radio signals to transmit the same message to different locations. In the US, the FCC requires that any station that wishes to communicate with an area code of more than fifty thousand households must choose a unique local carrier. For many other countries, like many in the UK and Australia, this requirement is not followed and broadcasts are sent out as multiple broadcasts of the same message.