Having a bit trouble figuring this one out, I have my iPad and garmin 660 bluetoothed to the GDL 39 3D, I know the iPad when connected this way derives its GPS positioning data from the GDL 39 but does the Garmin 660 also use the GDL for its positioning or does it continue to use its internal receiver. I'm going to run an antenna and trying to figure out which config will make for the best reception