Aluminum Bumper= Better Signal?

[tat21985]

Long story short, I grew tired of my bulky Otterbox and ordered an aluminum bumper from Amazon. I was a little hesitant after reading about the signal issues with metal cases.. I have ran several trials since receiving the bumper, and regardless of where I am in relation to a tower, the signal (dbm) is always lower (better) with the case on.. Have I found an anomaly, or is everything I've read about dbm's wrong?

 

[meyerweb#CB]

The antennae in the GS3 are in the back of the phone, not the sides, so if the aluminum is only around the edges of the phone I wouldn't expect it to have much effect on the signal.