Already back in 2007 when I got my first HSDPA data card I was quite surprised how big the difference in terms of data transfer speed was when a mobile device's antenna was just moved by a few centimeters. In the meantime, better receivers and noise cancellation must surely have done away with this!? Turns out that this is not the case at all.
Recently, when being in the countryside with very weak network coverage, I managed to only get around 50 kbyte/s throughput with my 3G dongle and very unstable connections. But with some measurement equipment I finally found a spot in my room where I could get a sustainable and rock solid data rate of around 750 kbyte/s, i.e. around 6 Mbit/s (Dual Carrier 3G dongle...) in the downlink direction and around 3.5 Mbit/s in the uplink direction.
The screenshot on the left shows the remarkable difference (click on the picture to enlarge). The low throughput on the left half is in various spots in the room while the right throughput shows what is possible from one corner in the room. Just 15cm away and we are back at 50 kbyte/s. Remarkable!
Even with an old HSDPA category 8 dongle I could still get around 400 kbyte/s in the downlink direction. I did not quite expect that because that is more than half of what is possible with the dual carrier dongle, even though that category 8 stick does not have the same kind of interference cancellation techniques of the dual carrier stick. Again, something I did not expect.