I have a microcell. I put two iPhone 4's on a desk 3 feet from the microcell. Both have 5 bars and indicate "AT&T M-cell" as the network.
I put my hand, palm up, on the desk under the phone, with my thumb where the volume buttons go, and my other fingers curled on the other side. This lifts the phone about 2". Each phone loses bars, one at a time, over the course of about 30 seconds, until even the "AT&T M-cell" indicator goes away. As soon as I put the phone back on the desk, I'm back to 5 bars.
Same experiment in a different room, on a different floor of my house. Start with 5 bars microcell. Same result.
Turn off microcell. Go outside where I can get 3 bars reception. Put phones on picnic table and repeat. Same results.
These things are broken. (At least my two).