I've extended my mobile internet access infrastructure and added an external antenna in order to assert a 3G signal so that the Huawei E970 router (T-Mobile webnwalk Box IV) does not switch to GPRS. So far, the experience has been excellent: in contrast to the E970's internal antenna I've permanently a 3G signal (HSDPA) and thus a fast mobile internet connection. Still, the external antenna had to be directed properly; a first attempt (inappropriate direction) yielded only unstable results.
Here is an alternative for an internal 3G antenna that you can install close to your desktop.
