When we think of wireless communication, the most popular use of this is radio.
Radio is the process of sending or transmitting electrical energy via waves from one place to another. To complete the process there must be a transmitter sending the wave and a receiver receiving it.
The radio waves consist of a mixture of electromagnetic energy. All these waves have a specific speed, length and frequency. The speed relates to how fast the signal is transmitted between two places, while the wavelength is the distance between one crest or wave peak to the next. Frequency is the number of waves that are received per second.
A programme, like what you listen to on the radio is transmitted by adding it to a radio wave called a carrier. This process is called modulation.
When the radio programme is added in a way that causes fluctuations to the carrier’s frequency, this is called frequency modulation (FM).
Another method of modulation is to make the peaks of the wave bigger or smaller, this is known as amplitude modulation (AM).
How does this work? Well, radio waves always draw comparisons with the sea and this is an ideal way of explaining it.
If you are on one island and trying to send a signal to another island via the sea, you could put an oar in the water and move it up and down quickly. By creating this wave quickly and varying its frequency, this is an example of FM.
Another method would be to splash the oar in the water up and down to make big waves. On route to the other island there will already be other waves and currents; the waves you created will make these even bigger and you will therefore be using these existing waves as a carrier to send your signal. As the method is to make the height of the carrier wave bigger, this is an example of AM.
So, FM and AM are basically working the same, the key difference is how the carrier wave is altered or modulated. AM changes the strength of the carrier wave; it amplifies it with the same frequency, while FM varies the number of carrier waves that will be received per second; it varies the frequency not the strength.
Both modulation methods are susceptible to interference of their amplitude, for example if there are other waves moving between the two islands that we are transmitting and receiving signals to and from, our waves may be lost or impacted on-route.
So, if the signal isn’t lost completely like when you go into a tunnel, for AM signals the by-product of amplitude interference is static. With FM waves, as amplitude is not how the carrier wave is modulated, the interference this causes is not an issue and therefore no static will be received. This is why we can notably hear this difference when switching between AM and FM radio broadcasts.