Electronic – How does a low power device make a direct uplink to iridium satellite


I was always fascinated by this idea. You are literally able to communicate or open a web browser from anywhere in the world. I am OK with the low power device able to receive data from satellites, but directly transmit the signal.. How is it doing it? It doesn't even have a parabolic antenna.

Take a look:
small module

Best Answer

It is a matter of link budget.

The people who designed Iridium did their homework and saw that the tiny fraction of those 2 watts that reached the big parabolic antenna of the satellite was sufficient. And for most cellular systems, you make cheap and low power terminals, while the base station (or satellite) has very expensive receiver equipment and high transmit power to compensate for the cheap terminals.

I found a very detailed paper on the subject, first describing the theory, then benchmarking the theory with actual numbers from Iridium. Rocket science level of the text though.