# Section 7 - Electromagnetic Compatibility (EMC)

## 7.1 What is EMC?

Electromagnetic compatibility is defined as 'the ability of a device, equipment or system to function satisfactorily in its electromagnetic environment without introducing intolerable electromagnetic disturbances to anything in that environment'. It has two main aims: to prevent pollution of the RF spectrum so that it can be used for radio communications, and to ensure that equipment which does not use the RF spectrum is able to operate correctly in the presence of the RF fields that exist in the environment. It can cover both radiated signals and those conducted down cables, e.g. transients on the mains. Examples of the pollution include interference from arcing thermostats, noise from computers, or spurious emissions from transmitters. An example of inadequate immunity to RF fields is when hi-fl equipment detects radio transmissions which can be heard on the system's loudspeakers

## What does that mean ?

EMC is basically the ability of one piece of electrical equipment to function without stopping another piece of equipment from functioning. From our point of view it is most important that we begin to develop an understanding of how our radio equipment, particularly our transmitters, may affect other electronic items around them, not just in the same room or house, but in neighbouring properties too. EMC generally, and TV interference especially, is one of the biggest potential dangers to being able to enjoy the hobby while still maintaining good relations with your neighbours, and indeed your own family.

It is almost impossible to convince the non-radio amateur that you are doing nothing wrong if your hobby is causing them a problem. EMC issues are not limited to television and radio interference, although these are the most common initial complaints. Other commonly affected items include telephones, hi-fi systems, computer monitors, burglar alarms, hearing aids, games consoles.... the list really is endless.

It is generally difficult to undo damage done to the relationships we form with other people, like our neighbours, so prevention is clearly better than cure. To this end, we must will learn a little about how interference is caused, and how to cure specific cases of interference. The key to good EMC management lies in the design of the station itself, so close attention should be paid to these sections.

As electronic devices become more and more integral to our lives, so the importance of EMC only continues to rise. Obviously we must therefore expect that assessments will include significant amounts of questioning on the subject. We will deal with EMC in greater depth in the higher license classes.

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