jrodhotrod said:The two major providers have slightly different technologies, but the principle is the same:
You have satellites that cover the contenintal United States. As long as you have line of site to those satellites you have a signal. For the most part it's either on or off, no static. However in populated areas they have set-up ground repeaters to help with coverage. The areas that these repeaters are in vary by company and so does their effectiveness.
For my commute from Morgan Hill to Sunnyvale, I typically lose signal only once for a brief bit, and that is at the 280/680/101 interchange and the mass of concrete that I have to pass under.
Occasionally I'll lose signal for a moment under other overpasses but not often.
for a more detailed description: http://electronics.howstuffworks.com/satellite-radio.htm
once we are on the highway, no sweat at all. maybe its the specifc channels she listens to have poor broadcasting strength or on a diff sat or somethign.