eli5: what’s the difference between AM radio and FM radio?

Question

i don’t understand when i google it so Whats the difference

In: Technology

Answer 1

If you want to transmit a tone, you need to encode it on a so called carrier wave.

If for examle a station is on 100 MHz, that means 100 MHz is the carrier frequency.
This is basically an electrical signal going from its minimum voltage to it maximum and back 100.000.000 times per second.

Now if you want to encode an audio tone on it you can do that in many ways, AM and FM being common.

In case of FM, which stands for Frequency Modulation, the encoding is done by slightly varying the carrier Frequency. For example by making it swing between 99.999.900 and 100.000.100 times per second, around that centre of 100.000.000, the quicker you let it swing between those two, the higher the tone being transmitted. If you make the swing bigger, for example to 100.000.200 the tone will be louder.

In case of AM, you don’t swing the Frequency of the carrier, that is kept constant. For example on 600 kHz, which means going from minimum voltage, to maximum and back 600.000 times per second. But now to put a tone on it, we will vary what exactly that minimum and maximum is. And that variation will be equal to the tone on being transmitted.