system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does satellite television require a dish to receive, but satellite radio doesn't?
gpt
The satellites are in different orbits.

TV satellites are in geostationary orbit, so they appear to be "fixed" in the sky so dishes can be rigidly mounted to point at them. Dishes have excellent reception characteristics, so they can receive the large amounts of data required for many channels of HD video. 

Radio satellites (Sirius, for example) are in lower elliptical orbits. Because they appear to pass overhead across the sky, a dish would have to swivel to point at them as they moved which is impractical. Instead, an omnidirectional receiving antenna is used -- one that does not need to be aimed. The drawback to the omnidirectional antenna is that it cannot receive very much data, so only audio programming (or, theoretically, a tiny amount of video programming if they chose to deploy it) can be received with it.