XM is a digital signal delivered by satellites (and in larger metro areas, ground based repeaters)
Because of its digital nature its ethier there, or not.
The antenna that comes with the PCR is a directional antenna. It is desiged to be pointed in a particular direction. It will not work well in a mobile enviroment. For that you need a automotive antenna. There are 2 types of antenna. dual lead and single lead. Dual lead antennas are the older type. Usually found on factory installed XM tuners and older generation XM receivers. Single lead antennas are the newer standard. All XM receivers currently being manufactuered use this type of antenna. The PCR is of the single lead design. You can use ANY single lead XM antenna with it.
This auto antenna:
http://store.myradiostore.com/blxmmianxm.html is great for the PCR. Like any XM auto antenna it should be placed on the roof. This antenna is a magnent mount antenna. Just stick it on. The antenna itself actually sits up on 4 small neopherene feet, to keep from damaging you car's paint.
XM was degisned originally for automotive use, thus reception is great when using the correct antenna. As long as the southern sky is not entirely blocked you will receive a signal just fine. And in metro areas XM has a rather large network of ground repeaters. These repeaters will get the signal to you through things the satellites cannot (such as overpasses, tall buildings, and parking garages)