Radio waves are made by various types of transmitter, depending on the wavelength. They are also given off by stars, sparks and lightning, which is why you hear interference on your radio in a thunderstorm.

Radio waves are the lowest frequencies in the electromagnetic spectrum, and are used mainly for communications.

Radio waves are divided into:-

Long Wave, around 1~2 km in wavelength. The radio station "Atlantic 252" broadcasts here.

Medium Wave, around 100m in wavelength, used by BBC Radio 5 and other "AM" stations.

VHF, which stands for "Very High Frequency" and has wavelengths of around 2m. This is where you find stereo "FM" radio stations, such as "Galaxy 101" and "GWR FM". Further up the VHF band are civilian aircraft and taxis.

UHF stands for "Ultra High Frequency", and has wavelengths of less than a metre. It's used for Police radio communications, television transmissions and military aircraft radios - although military communications are now mostly digital and encrypted.

Large doses of radio waves are believed to cause cancer, leukaemia and other disorders. Some people claim that the very low frequency field from overhead power cables near their homes has affected their health.