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How Does Amplitude Modulation Work (AM)?

What’s amplitude modulation? How does AM work? How does amplitude modulation work? Antique radio restoration. Before I explain the detector circuit, it’ll be helpful to discuss how the audio signal is encoded in the IF. So far, I’ve told you that a radio station’s transmitted frequency, called the carrier frequency, is encoded with the audio signal, which is passed to the IF signal. The graphic I’ve shown to represent this has sufficed to this point, but now I want to use an oscilloscope to show you what the signals really look like. On the top display I’ve input a 456 kilohertz signal into my oscilloscope, the same frequency as the IF. The X axis represents time, and the Y axis represents signal strength. Our signal goes from zero to positive, back to zero, to negative, and back to zero 456,000 times a second. Now lets take a look at an audio tone of 1 kilohertz. The signal goes from zero to positive, back to zero, to negative, and back to zero one thousand times a second. Encoding the IF with the audio is done using amplitude modulation, or AM. This means that the audio signal modulates, or changes, the amplitude of the IF radio signal. This is easily seen on the oscilloscope. Compare the unmodulated IF signal with no audio. With the same signal with modulated audio. The width of the signal hasn’t changed, because the frequency is still 456 kilohertz. But the amplitude is now going up and down, in relation to the audio signal. Here, I’ve connected a radio signal generator to the oscilloscope with an unmodulated 456 kilohertz signal. The radio signal is shown on top. I’ve also connected a music source to the oscilloscope and that signal is shown on bottom. And here I’m modulating the radio signal with the music signal. Notice how its amplitude changes in relation to the music. Radios like our antique Emerson are called AM radios because they use amplitude modulation. FM radios work similarly, but instead use frequency modulation. #radiorepair #radio #electronicsrepair #restoration