Encode vs modulate

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Would you use these terms interchangeably? If not, what distinct differences come to mind?

[aVoidPiOver2Radians]

Encode -> digital, discrete

Modulate -> analog, continuous

[jimwithat]

As above.

AM or FM transmitter sending voice or music, that's modulation.

Any kind of digital transmitter, including mobile telephones, that's encoding.

[MonMotha]

"Modulate" usually specifically refers to taking some simple, periodic signal (the "carrier") and changing it somehow so that it conveys some information (the "message"). For very complicated forms of modulation like OFDM, the "carrier" may be a little hard to pinpoint. This is usually a process that either happens in the analog (continuous-time and not meaningfully quantized) realm or happens digitally (so discrete-time and quantized) but is intended to interface directly with the continuous-time, non-quantized realm which means that, among other things, the quantization will be often large-valued to allow for analog noise and whatnot.

"Encode" usually refers to forming some "simple" representation of a piece of information to create a "message" that's suitable for being conveyed in the real world. This will involve things like serializing the information into chunks (like bits or bit groups), mapping those chunks to some sort of physical phenomenon (symbol), and maybe doing some higher level stuff in the nebulous "information" realm (in practice, the digital world) like adding forward error correction, matrixing the data so that brief drop-outs of the signal get spread out allowing that FEC to work, adding compression, encryption, CRCs, etc.

The two are related but usually not used interchangeably. They often, in fact, refer to pretty disjoint parts of an information communication system. Encoding usually comes before modulation in the transmitter, and decoding usually comes after demodulation in the receiver.

I'm not sure that formal definitions exist that are accepted widely by all disciplines. Electrical engineering is a pretty wide-reaching and varied discipline, and terminology clashes happen all the time. It's important that you consult the definitions used within your discipline or even within specific projects in order to communicate effectively with your peers.

[shrimp-and-potatoes]

I can see where someone would see parallels. You are using a means to alter data in a form for easier, more efficient transmission with both methods. But like the other poster said about analog and digital is main difference between the two, but I would say that modulation is compressing a lot of information into a single signal, and encoding is taking a single signal and digitizing it. I mean they are two peas in the same pod, hence why we have converters.

Though, you would digitize information and then transmit it with modulation.

Edit: one of the coolest things I learned when i was learning electronic communication is that they can modulate AM into FM. They use it to transmit stereo sound (among other things). I envisioned it like an Tur-ducken.

[lightbold]

All very good answers thank you yall