o modify (modulate) the carrier and in this way the information is superimposed onto the carrier and is transmitted to the receiver. Here the information is removed from the radio signal and reconstituted in its original format in a process known as demodulation. It is worth noting at this stage that the carrier itself does not convey any information. There are many forms of modulation that can be used to modify a carrier. Each one has its own advantages and disadvantages and can perform well under given circumstances. Some of the simpler forms of transmission have the advantage that receivers needed to resolve them properly are not as complicated. On the other hand, other modes which need more complicated circuitry to resolve them may perform better in one aspect or another. Radio carrier The basis of any radio signal or transmission is the carrier. This consists of an alternating waveform like that shown in Figure 3.1. This is generated in the transmitter and is usually passed to the output of the transmitter where it is radiated for reception by the receiver. The transmission may be anywhere within the radio spectrum described in Chapter 2. 52 Newnes Guide to Radio and Communications Technology Figure 3.1 An alternating waveform Morse Morse is the oldest and simplest way of transmitting information using radio. Yet despite its age it still has some advantages, and this means that it is still in use in some areas today. One of its advantages is its simplicity. It only consists of a carrier wave which is turned on and off as shown in Figure 3.2. The characteristic dots and dashes are defined by the length of time the transmission is left on. The dots and dashes then go to make up the required letters. The simplicity of the Morse code and its implementation means that equipment for sending it can be much simpler than if another mode had The letter 'N' in Morse Figure 3.2 A Morse signal Modulation 53 been used. This can be an advantage for amateur radio enthusiasts as it enables them to build their equipment more 