Hi...this will be the second time I will be doing this to a Jetta...I'm removing the radio/CD player from my 2014 Jetta and will be adding the RNS 315 unit. The prior time I did this (in a 2013 Jetta Wagon), I placed the GPS antenna behind the radio inside the dashboard (per the suggestion of the mechanic that sold the unit to me) and it worked great. I plan to do this to my 2014 Jetta, but I want to add the Sirius radio antenna too. Everything I've read said it has to be outside the car (for best reception) or on the dashboard (for moderate/okay reception). This is the part I do not understand. If the GPS antenna works fine INSIDE the dash, why can't I put the Sirius antenna INSIDE the dash as well instead of ON the dash? They both work off satellites and the GPS antenna has no receptions issues. Thoughts?