boosting my 3g signal on nokia 5800?

[paul d]

I use the internet a lot on my nokia 5800 but in the area i use it most of the time it varies from good 3g signal to not at all and reverts to the slow gprs. Is there anything i can buy (not too expensive) that would improve my 3g signal or something i could put where the 3g signal is strongest and then my phone in the position where 3g is nil would pick up that something and get strong 3g (know what i mean!!)