[rocho]

Wow, I never thought about how Voyager communicates with Earth. But now I wonder: if Voyager just sends photons towards the Earth, at the receiving end how are we recognizing which photons are coming from Voyager and how is the "signal" decoded?

[RachelF]

Two main reasons for recognizing the photons: They have a specific frequency, 8.3GHz in this example. It's like tuning an FM radio to a station. The photons are coming from a specific direction.

As to how they are decoded, you'll need to understand some modulation techniques.