---
tags: [radio]
created: Sunday, July 06, 2025
---

# Radio basics

Radio is the technology of communication or exchanging information using radio
waves.

Radio waves are electromagnetic waves that transmit at a certain frequency of
the [electromagnetic spectrum](./Electromagnetism.md): between 3Hz and 300GHz.

![](../img/em-spectrum-radio.jpg)

This makes them the lowest in frequency and the longest in wavelength.

Radiowaves are generated by an electronic device called a **transmitter**, which
is connected to an **antenna** which radiates the waves out into space.

These waves can be detected by another antenna connected to a radio
**receiver**.

Information is transmitted by adding information to the raw electromagnetic
wave. The wave by itself doesn not contain any information.

The wave form used is a sine wave that fluctuates smoothly and consistently.

There are two main methods of adding information to the waveform: AM and FM.

AM stands for **amplitude modulation**. Here, the amplitude of the wave is
altered. The amplitude is the distance from peak to peak. For example, the sine
wave produced by a person's voice is overlaid onto the transmitter's sine wave
to vary its amplitude.

FM stands for **frequency modulation**. Here, the frequency of the wave is
altered. The frequency is the number of oscillations over a given time period
which we measure in Hertz.