FM Radio - Free Music on Every Corner

Radio is probably one of the most popular free services. We can listen to it just everywhere. At home, at work, in the bus, in the car, while we walk, etc. With the term "radio" we usually mean a sound service that we can receive and is usually free, without any subscription or expensive equipment. With radio you also get free music. You can listen to it while working or you can relax and enjoy listening to your favorite band. There are many ways to get such free sound service. Each has some advantages and disadvantages but the fact is that the old FM radio as we know it is far the most widely used broadcasting service.

You can listen to radio stations that are broadcasting over internet. This service is still free, but you need access to the internet and a computer. There are also some devices (network players) that support internet broadcasting, but you still need access to the internet, either wireless (WiFi) or over local network. The advantage of internet broadcasting is that there are thousands of stations so it easy, at least in theory, to find a station that plays music according to your taste. Cable and IPTV systems also offer radio stations but this is limited to the place where you have the connection.

Satellites also offer a lot of radio stations. But to receive satellite stations you need a satellite receiver, so this type of reception is only suitable for home listening. There are also mobile satellite radio services, but in general they are not free. You have to pay a subscription. Despite the fact that satellite services are cheap and you get large coverage areas, this type of broadcasting is not suitable for general reception. Satellites do offer a huge choice of stations, but the receiving equipment is pretty complex.

Therefore, terrestrial broadcasting is the most popular platform for radio. While AM broadcasting is still used in some countries, mainly for international broadcasting, it is the FM radio that we can find it on every corner. There are many reasons for its popularity. It is free, you only need a simple and cheap receiver. Receivers are now integrated also into mobile phones, MP3 players and many other devices. The quality of FM (frequency modulation) is very high. With quality stereo reception and some high-end receiver you get superb sound quality comparable to vinyl records.

Because of many advantages of terrestrial broadcasting there are many stations interested in using this media. Of course, the radio-frequency spectrum is a limited resource and only a small fraction of the whole spectrum is allocated to broadcasting. Therefore, we can fit only a limited number of stations into this band. In addition to this, to prevent harmful interferences there are many strict rules on frequency planning which further limit the number of possible radio stations that we can receive.

But despite all the disadvantages and limitations the FM radio will be used for many years to come. Interestingly, there is still no comparable digital broadcasting system that could replace the old analog radio.

FM Radio - Any Digital Alternative?

FM radio is a well known and used technology. It is used all around the world. There are some minor differences in modulation parameters and frequency bands but the basic principle is the same. It is amazing how popular this radio has become. FM radio receivers are found everywhere, even in mobile phones. In the last decade broadcasting has made a big step toward digital technologies. We are now in a phase of transition from analog television broadcasting to various forms of digital broadcasting. And television is far more complex than radio--simple stereo sound service. Why is there no suitable technology for digital radio?

The answer is pretty simple. We have to look at key aspects of the transition of television broadcasting. Analog television uses one frequency channel (from 6 to 8 MHz bandwidth ) for one program. Digital television broadcasting is using the same radio-frequency channel to broadcast multiplex--a digital package of many TV programs and other services. The advantage is obvious--using the same radio-frequency spectrum we can now broadcast many TV channels and other services. Therefore, digital television broadcasting means more efficient use of frequency spectrum. There is another very important aspect of digital TV broadcasting. Since both technologies are using radio-frequency channels with the same bandwidth it is possible to switch from analog to digital step by step. Such change from one technology to another usually takes years and needs detailed preparations on a large scale.

To switch from analog FM to digital broadcasting we need a suitable technology that will offer comparable quality, mobile reception, capacity for more radio stations, efficient use of radio spectrum, step by step transition and cheap receivers. There are many digital technologies that are already available for sound broadcasting. Unfortunately, none of those technologies is suitable for a direct replacement of existing analog broadcasting.

Currently there are already many efficient audio codecs that can be used with any digital technology. There are also digital transmission technologies suitable for digital sound broadcasting like T-DAB, DRM and DRM+. DVB-T and DVB-T2 in particular can also be used for radio. All those technologies can provide excellent quality and mobile reception. But this is not enough.

FM radio uses about 250 kHz wide channels. Channel spacing is 100 kHz in most parts of the world and 200 kHz in USA and some other countries. This combination of channel bandwidth and spacing makes it very difficult to simultaneously use analog and digital broadcasting. Therefore, the transition with existing technologies will be difficult. Some partial solutions like HD radio are nothing more than additional data and audio transmitted along main analog carrier.

There are probably only two possible approaches for the digitalization of FM band. Either to find a suitable technology that will satisfy all the above mentioned requirements or to select one technology that is future proof enough and make a totally new frequency plan for fast transition. Currently, the digitalization of frequencies used for FM radio will have to wait for a while.