Satellite radio uses the 2.3GHz S band in North America, and generally shares the 1.4GHz L band with local Digital Audio Broadcast (DAB) stations elsewhere. It is a type of direct broadcast satellite, and is strong enough that it requires no satellite dish to receive. Curvature of the Earth limits the reach of the signal, but due to the high orbit of the satellites, two or three are usually sufficient to provide coverage for an entire continent.
Local repeaters similar to broadcast translator boosters enable signals to be available even if the view of the satellite is blocked, for example, by skyscrapers in a large town. Major tunnels can also have repeaters. This method also allows local programming to be transmitted such as traffic and weather in major metropolitan areas, though this is not yet implemented.
Each receiver has an electronic serial number (ESN) to identify it. When a unit is activated with a subscription, an authorisation code is sent in the digital stream......
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