The Physics: Why Phones and Satellites Struggle to Talk
Why is connecting an ordinary phone to a satellite so hard, and what do satellite designers do about it?
Chapter summary
A phone transmits about 0.2 watts through an antenna with almost no gain, and a satellite in low orbit is 300 to 1,000 kilometres away, compared with a few kilometres for a cell tower.
Key takeaways
- 1
The signal arriving at the satellite is about a million times weaker than at a tower.
- 2
Satellite designers close that gap almost entirely on the satellite side: with very large phased-array antennas that concentrate their sensitivity into narrow beams, with lower orbits that shorten the distance, and with modest data rates per user.
- 3
Antenna area is the single most important design choice in D2D, which is why AST SpaceMobile's satellites fly arrays of 64 and then 223 square metres and why SpaceX's next generation flies at about 330 kilometres.
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From Satellite Phones to Smartphones: A Short History
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