| Radiocommunications Agency
EMC Awareness was originally prepared by Keith Armstrong and Tim Williams for the Radiocommunications Agency now known as Ofcom. It is with their kind permission that we are presenting these files. Some parts of the website, mainly the links, are in the throes of being updated. If you should find any links that do not work please email pam [at] nutwood [dot] eu [com]
This site aims to promote awareness of Electromagnetic Compatibility, particularly with respect to radio frequency interference: what are its causes and manifestations, and what designers and installers of electrical and electronic products can do about it.
Radio interference problems are many and varied. The diagram below illustrates how radio transmitters can interfere with electronic systems, and how electronic systems can interfere with radio reception.
For interference to occur, we need several coincidences:
a source of interference;
a victim of that interference;
a coupling path between them;
the source must be emitting on a frequency at which the victim is susceptible;
it must be emitting at a time when the victim is operating;
the interference must be at a level which is noticeable and significant.
Given that all these must happen together, it isn’t surprising that radio interference is not an everyday occurrence for most people, despite the proliferation of electronic and radio products around us. Even so, there are some circumstances in which it happens frequently, even continuously, and is accepted as such; there are some times when it happens infrequently and is a nuisance; and there have been some occasions on which it happened only once but the consequences were disastrous.
Yet experience has shown that designers of electronic systems can do a lot to mitigate the occurrence of RF interference. Products can be designed for good immunity to RF fields, and they can also be designed to minimise the generation of disturbing signals. Legislation is now in place to insist on minimum standards for these characteristics, and some manufacturers expect good EMC from their products as a matter of course, but this is not universal.
This website will hopefully improve the situation. There are sections which describe real life examples of EMC problems, mitigation techniques which can be applied in product and system design, the compliance regime in place throughout Europe, and Frequently Asked Questions on EMC. References are provided wherever possible. We hope you find it useful.
Written by: Keith Armstrong and Tim
Web Design: Sandy Armstrong