Radio Principles

No5. Modulated Amplifier

At this stage we have now generated and amplified both the carrier and the audio signal that will modulate it and we can now marry (or more formally heterodyne) them together. This is the process of modulation whereby the low frequency audio signal is mixed to a high frequency RF carrier which can then radiate. At this point in our model high-power system we will have very large voltage values for both the carrier and the signal and will have to use valves as semiconductors will not withstand the power dissipated. A common circuit, known as the plate modulation system, is shown below.