I have a Sirius Radio in my car that has both AUX and USB ports. The subscription just expired. I would prefer to have a portable that I could take from a "dock" in my home/office and plug into the AUX or USB connection on the existing car (equipped for satillite) radio. Is that possible? If so, will the portable unit (once plugged into the car's unit) find the signal using the vehicle's satillite antenea?
no, each sat. radio device needs its own antenna.
and before you ask, most factory antenna's use proprietary connections, and possibly software to decode the signal, so it is not very likely that you can hack the factory antenna, unless your are very familiar with satillite wiring and programming.