My N3 is installed in my C5 Vette and is an excellent unit. As you may know, there is a display of satellites available showing the number seen and when they are "locked" to phase tracking. My GPS antenna and XM antenna are placed forward on the dash, each one about 9 inches off center. I was seeing 3-4 satellites with a long lock time to nav solution until I made a piece of stainless shim stock into a plane and fitted it around the GPS antenna.. Now I usually track 7-8 satellites with rapid lock/solution times. Mine is 3 inches square. Along one edge I placed the GPS antenna longways on the centerline, traced its outline, and snipped out the traced portion. I then slipped it around the GPS antenna... Viola, much improvement in performance. The same treatment applied to the XM antenna resulted in decreased performance.... probably due to the much higher frequency of the XM band.. Likely I willl experiment later with a different dimension plane for XM... If there is interest I can possibly photo and post..

Thats probably why they give you that sticky metal square piece with the GPS antenna

Like many in this forum I got my N3 used off the Bay. Little sticky pad was not in the "professionally wrapped and boxed" package. I have also found that a lot of "professional" installers will not use it since dash mounting works to a degree. I just found a way to make it work better and posted here to help.