>USRP system? That could be very illegal, though.
If used with devices like this one, I think there are no problems at all:
http://www.rfshieldbox.com/datasheets/tc5910c.pdf
I own one of them and it is rather handy without requiring an anechoic chamber
Agreed... but the network operators often don't see it that way :-) During my time I was tech lead on a number of "Major Criminal Cases" (The Major bit in my opinion is entirely optional... ) assisting the police with locating the evil dastardly criminal depriving the network operator of their hard earned revenue/profit.
I mean yes, I know there is criminal stuff surrounding the frequency bands and radio allocation, and all that stuff, but the way the Network Operators used to go after some of these guys, you'd think they where major organised crime villains.
Don't get me wrong, there where one or two that deserved what they got, but vast majority where just trying to make life better/easier for them selves.
Not going into details, but the one I always remember was the farmer who used to be a radio engineer, and built his own mast then hooked it into the local networks, then let the folks in the village in the valley below his farm use it for free. He and most of the villagers had complained for years (Typical deep welsh mining valley, almost like going into another world) about the lack of a decent mobile signal, so he solved the problem. Folks connecting via his mast still had to pay thier own operator charges, so it's not like he was giving folks free calls or anything.
Anyway (I think it was One2One at the time who lead the investigation) we eventually found the transmitter, and the network went after him for everything. Took his land off him, got the mast pulled down, and erected their own on the same spot, took his farm off of him, fined him thousands, and got him locked up for 2 years under various trumped up criminal charges, all of it backed up by the courts.
But anyhoo... I digress.... :-) getting a bit side tracked there.... LOL
Iv'e been out the game for 10 years now, so no idea what things are like these days.