XM reception issue

I have had an after-market XM receiver on one of my other cars for almost 5 years. I had XM added as a dealer installed accessory to my 2010 Prius II. I've always heard that after-market satellite receivers had more reception dropouts than installed units. However, I'm having significiantly more dead spots with the Prius. At times I'm at a loss to determine a South side structure or grove of trees which could possibly explain it. Short in the cabling? Radio performing multiple tasks (AM,FM, XM) not as weel as XM specific receiver? Antenna performing multiple tasks not as well as single task? Thanks for any suggestions! Steve

 

I appreciate the response, but my question is not a Sirius vs. XM issue. Whole different thread. I've had a lengthy experience with XM in my other car and I know the few types of spots where I expect to have reception issues (in parking ramps, sitting under interchanges waiting to make a left turn, and sitting at a stoplight immediately next to a building are likely candidates). The Prius XM, however, has additional dropout points, some of which make no sense in specific places where my other car breezes (to this day) through with no problem.

In one perplexing instance I came out of a SuperTarget and turned left (West) on a four-lane. I was in a lane some distance from the southside single story outlying strip mall in front of the ST and I had about 7 seconds of dead air. Shortly thereafter, I returned toward the East past the same strip mall, which was now next to me on my right (South) side and I had no drop off. If anything, the occurrances should have been reversed. The antenna could be somewhat directionally challenged or perhaps there is a short in the cable. The Toyota dealership will look into it, but I've given them all the help I can (other than loaning them both cars to test out). Steve