receiver orientation

I always used to install 2 way receivers near the rear view mirror with the pole pointing down or toward the front of the vehicle. In the last couple years, I started installing them sideways, with the pole facing the pillars. I thought I read somewhere that this was better, but I cannot remember where so I thought I would ask if anyone has done any case studies on this or if they had any opinions on which orientation is better for range. Thanks

i dont think it matters, its just an RF receiver like a cell phone

I've place them in the dash, behind the "A" pillar trim, on a rear quarter window, MR2 and 911, behind the inst panel BMW E46, above the glovebox BMW E36 and it doesn't seem to make the slightest difference, the only exception being cars with metallic windscrens, some Audis, M/Benz etc. Hell I've even mounted one on plastic adjacent to the rad grille on a Merc.