I have a Pearl 8100 unit. I have been given an aluminum cover for it. When you put the unit in the cover the reception or signal strength reduces by at least half. The cover does have cutouts for the camera and side controls etc but I assume that the cover is blocking out reception.
If some one can give me an idea as to roughly where the internal aerial is on the unit I would like to create another cutout to see if this solves the problem.