How is Sirius XM radio different than AM/FM.. I know AM is radio transmissions created by changing the power of the carrier wave, and FM are transmissions created by changing the speed at which radio waves are generated.

Answer 1

You have a great misunderstanding.

AM: the amplitude of the carrier wave is modified slightly, average power does not vary much.
FM: The carrier frequency is lightly modified by the information, amplitude largely remains the same.

Now both of those signals have a magnetic and electric field that are 90 degrees to each other. Normally, AM radio uses vertical polarization (notice how car antennas go upwards). FM radio is largely in the US Horizontal polarization, as are tV stations.

Nowadays, FM stations in cities usually transmit "mixed" polarizations, which have components horizontal and vertical, these can penetrate buildings easier.

Now XM "satellite" radio is quite another system. Two satellites, transmitting on six channels, half of it duplicated for redundancy, and a large number of land repeaters (about 900). A typical city has about 20 land stations. The information received by a receiver is digital, and has to be decoded. To ensure signal reliability, two signals of three channels each reach the receiver, and are digitally processed. At the signals are a commbination of land, and or satellite digital signals, the user cannot know easily. The modulation used is a common type, phase shift keying, used in digital communciations. The polarization from the satellite is circular, from the land stations, mixed.