Chapter 6: Television & Satellite Communication
6.1 How Television Signals Work
TV works on the same principle as radio, but with much more information. A TV signal must carry both picture and sound — requiring far more bandwidth than audio alone.
Modern digital TV encodes everything as binary data, compresses it, and transmits it digitally — producing much sharper pictures than analog TV.
6.2 Satellite Communication
A ground station transmits a microwave signal to a satellite (the uplink). The satellite amplifies it, shifts the frequency, and rebroadcasts it back to Earth (the downlink). A dish antenna on your roof picks up the signal.
📊 Diagram: Ground station transmitting uplink to a geostationary satellite, which retransmits the downlink to a dish antenna on a house.
Most TV satellites sit in geostationary orbit at 35,786 km, orbiting Earth once every 24 hours — appearing to hover motionlessly over one spot.
| Orbit Type | Altitude | Period | Use |
|---|---|---|---|
| Low Earth (LEO) | 200 – 2,000 km | 90 min | Starlink, Earth observation |
| Medium Earth (MEO) | 2,000 – 35,786 km | 2 – 24 hrs | GPS satellites |
| Geostationary (GEO) | 35,786 km | 24 hrs | TV broadcast, weather |
💡 Fun Fact: A geostationary satellite signal takes ~0.25 seconds for a round trip. That's why satellite phone calls have a noticeable delay — your voice travels 72,000 km!