transmission which can be applied to radio equipment 300 GHz which corresponds to a wavelength of 10-3 and which cannot be covered here but which need to be metres and lies in the EHF band of the radio frequency known to those doing safety surveys. spectrum. If the calculation is done the other way round, Much power is wasted in amplitude modulation and 300 GHz corresponds to an energy of 0.00125 eV which, various other forms which reduce the waste are widely from the foregoing, is too small by about four orders to in use such as single sideband (the two sidebands in AM cause ionisation. contain identical intelligence) with a reduced carrier However, in radio transmitters using very high supply power, double sideband where the two sidebands carry voltages, ionising radiation in the form of X-rays are different intelligence and again the carrier is reduced, etc. produced. It should be clear that this ionising radiation is The recent development of digital radio and television not inherent in the RF energy but rather that both forms will likely become widespread over the next few years. of radiation can co-exist inside equipment and the RF engineer or technician needs to be aware of the hazards involved. It is also the case that ionising radiation is, in lonising and non-ionising radiations most countries, subject to definitive legal provisions due to its hazardous nature. Confusion between these two forms of radiation amongst the public has been mentioned earlier. There is also Explanation of terms used a surprising amount of misunderstanding amongst elec- tronics and radio engineers about the distinction between In this section those terms and units which are most these two forms of radiation even amongst newly quali- fied graduate engineers, SO that RF radiation is sometimes frequently used in dealing with RF radiation are considered to be the same as ionising radiation. explained. The more formal definitions may be found in Ionising radiation, by definition, is radiation capable of reference books. Other more s