My iPhone Won't Pick Up Wifi, but my MacBook Pro Does

I have an iPhone 3G with me in my vacation in Germany. When I'm in the attic, I get Wifi from one of my neighbors (bless his soul). But, I only get the wifi on my MacBook Pro (17 inch, mid 2009), not on my iPhone. It has four bars on the Apple WiFi Fan on my MacBook, but the wireless network doesn't even show up on my iPhone. Only very rarely at night I might get one bar on my phone, but other than that, I get nothing.

Is the iPhone WiFi Antenna weaker than the MacBook? Or is something wrong with my phone? I had the same problem last year when I was on vacation, but I never posted it on Discussions.