Speech – this works rather like a telephone conversation, except that only one person may speak at any one time. Operators must identify themselves by their licence call sign during each transmission. Amateurs use different “modes” for speech, but today the most common are SSB and FM.
Morse – is still an effective means of communication which works with the very simplest equipment. As well as its effectiveness, the narrow bandwidth uses the radio spectrum most efficiently, allowing parallel contacts to take place within a small spectrum space. This is of great benefit in crowded band conditions.
Television – many amateurs transmit TV pictures to each other, often in colour. Normally the range of these transmissions is tens of miles. However, amateurs have pioneered a system called “slow scan” television (SSTV) which enables amateurs to transmit pictures around the world, albeit at a slow rate.
Data – many protocols exist and amateurs are in the forefront of developing new ones such as PSK31, JT65 and weak signal operation. For example it is now possible to use a radio situated on the other side of the world via the internet
Satellites – these can use any of the above but your signal goes up into space and back again. Most people think of man-made satellites but amateurs also use the Moon to bounce signals back, known as EME, or earth-moon-earth.