Hi all: Why is it that we have a dozen or so different electromagnetic wave types and yet every one of them can be used for analog and digital communication?
Thanks!
In: Physics
There really aren’t different type of electromagnetic waves. They are all the same and vary by frequency and amplitude. You see colors, those are electromagnetic waves of different frequencies. Amplitude would be the brightness of the light. Most frequencies of the EM spectrum you just can’t see because our eyes only detect a really narrow range of frequency.
Using visible light as an example: for analog you could vary the brightness of light (amplitude modulation; do it with radio waves and you might call it AM for short), or you could keep the brightness constant and change the color (frequency modulation; do that with radio and you might call that FM).
Digital signals are just when you use an analog signal to represent “1” or “0”. You can do that with amplitude (when the light is off or below a certain brightness it may be 0, and above a certain brightness, a 1). Likewise you could use frequency to encode the 1’s and 0’s, perhaps closer to red is a 0 and closer to blue is a 1.
The advantage of digital is that you can chose ranges of amplitude or frequency (usually frequency), that make it really clear when something’s a 1 or 0 AND there are tricks when sending digital information where you can detect and fix errors in communication, so the receiver has a very good chance of getting a perfect copy of the message sent, even if there’s stuff affecting the signal.
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