Any differences on amplitude modulation (AM), frequency modulation (FM) radio waves?

The first thing to understand is what modulation is and why it should be modulated. 

The is 20HZ-20KHZ, which is also the frequency after it is converted into an electromagnetic wave. Therefore, the audio needs to be carried on the high-frequency signal to transmit further, and the process of carrying the high-frequency signal on the audio is called modulation. 

Sound wave

The purpose of modulation is to transmit audio farther away. At present, there are two methods commonly used for amplitude modulation and frequency modulation.

The following picture is the most direct. "Amplitude modulation" is the modulation amplitude. The amplitude of the high-frequency signal changes with the amplitude of the audio signal. When the amplitude of the audio signal is high, the amplitude of the high-frequency signal also increases. 

At present, medium wave AM (frequency range 300KHZ-3MHZ) short wave SW (frequency range usually refers to 3-30MHZ, )

The amplitude envelope of the audio signal, but the frequency of the high-frequency signal has not changed; "FM" is the modulation frequency. The frequency of the high-frequency signal changes with the change of the amplitude of the audio signal. 

When the amplitude of the audio signal is high, the frequency of the high-frequency signal It also goes high, and vice versa goes low, but the amplitude of the high-frequency signal does not change.

Attention 

The first thing to understand is what several abbreviations mean: 

MW: Medium Wave ------ medium wave, 

SW: Short Wave ------ short wave, 

AM: Amplitude Modulation ------ AM, 

FM: Frequency Modulation ------ frequency modulation.

Unknowingly, there is an equal sign between MW (medium wave) and AM (amplitude modulation). In fact, MW (medium wave) is just a kind of broadcasting that uses AM (Amplitude Modulation) modulation. 

For example, the modulation method used in international short-wave broadcasting in high frequency (3-30MHz) is also AM (Amplitude Modulation), and even the higher frequency of aeronautical navigation communications (116-136MHz) than FM broadcasting also uses AM (Amplitude Modulation).

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