I'm doing an upgrade install from my Z3 to the 120BT. I'm also adding XM for the first time ever. In the XM's installation instructions (yeah.....I read 'em....what of it? 
, they say the following:
- To safeguard from electromagnetic interference
• In order to prevent interference, set the following
items as far as possible from this unit, its cables or
leads:
– TV antenna and antenna lead
– FM, AM antenna and its lead
– GPS antenna and its lead
In addition route each antenna lead as far as possible
from other antenna leads. Do not bind them
together, lay or route them together, or cross them
over each other. Increased interference could lead
to TV reception appearing fuzzy
I understand the part about not putting any leads near the "unit" which I'm assuming is the XM chassis/box itself. However, I'm a little unclear about why you'd have to keep the antenna leads away from each other. I assume that these are passive antennas so would not be radiating any RF on their own. I'd assume that there's RF coming out of the XM chassis iteself so keeping the antenna wires away from THAT box makes sense. Have you guys been routing the antenna leads away from each other and if so, how far apart?