Radio Communication and the Mobile Phone Georgie Winter
Radio Communication Mobile phones are a relatively new invention, yet radio technology has been around for over a hundred years – Marconi's first radio transmission was made in 1895. Now, over 40 million people around the UK enjoy the benefits of mobile phone communication.
Radio Waves Mobile phones transmit and receive signals using electromagnetic waves – otherwise known as radio waves. Radio waves have the longest wavelengths in the electromagnetic spectrum. These waves are emitted by many natural and man-made sources. Television, Radio and Mobile phones all emit radio waves. Electromagnetic radiation consists of oscillating electric and magnetic fields.
Frequencies Frequencies are measured in hertz (Hz) 1 Hz is one oscillation persecond – 1 kHz a thousand 30 kHz – 300 GHz are widely used for telecommunication such as radio and television broadcasts In the UK, AM radio uses frequencies between 180 kHz and 1.6 MHz FM radio ranges from 88 to 108 MHz
Radio Communication Using Amplitude Modulation (AM) A radio frequency wave used for radio communication is otherwise known as a carrier wave. If a radio wave is to convey information such as speech, this has to be added to the carrier wave in some way – this is called modulation. For Amplitude Modulation (AM) transmission, the electrical signal from a Microphone produced by speech or music is used to vary the amplitude of the carrier wave in proportion to the size of the electrical modulating signal. There are also Frequency Modulations (FM) and Digital Modulations used widely to modulate radio waves to carry different types of information.
Mobile Phone Networks and Radio Communication A mobile phone sends and receives information by radio communication. Radio frequency signals are transmitted form the phone to the nearest base station – incoming signals are sent from the base station to the phone at a slightly different frequency. Base stations link mobile phones to the rest of the mobile and fixed phone network.
Each base station provides radio coverage to a geographical area known as a cell. The cells overlap at the edges to ensure the mobile phone users always remain within range of the base station. Without sufficient base stations in the right locations, mobile phones will not work. If a person with a mobile phone starts to moves out of one cell and into another, the controlling network hands over communications to the next base station.