Probably the best way to test the real time 3G connection on your iPhone is with a ping tool. The one I used is a free app called Network Ping Lite. Download the tool and turn off WIFI. Open it up and choose the Ping utility. Enter an ip (you can use 18.104.22.168), scroll down to turn on "Ping forever" and then hit Start. Watch to see if you get a response and note the time in "ms". Then do whatever you think might affect the connection. If the times go up or if it stops responding you've affected the connection. Mine will sometimes start dropping pings almost immediately after putting the lower left corner of the phone in my palm. This is what happens in the screenshot below. FWIW, this doesn't bother me, I just hold the phone a different way.