Power

Any electromagnetic wave carries energy, or power -we can feel that when we enjoy (or suffer from) the warmth of the sun. The power P is of key importance for making wireless links work: you need a certain minimum power in order for a receiver to make sense of the signal.

We will come back to details of transmission power, losses, gains and radio sensitivity in chapter three. Here we will briefly discuss how the power P is defined and measured.

The electric field is measured in V/m (potential difference per meter), the power contained within it is proportional to the square of the electric field,

P ~ E2

Practically, we measure the power by means of some form of receiver, e.g. an antenna and a voltmeter, power meter, oscilloscope, or even a radio card and laptop. Looking at the signal's power directly means looking at the square of the signal in Volts.