all i can tell you is third hand information i gathered during my search for a solution... i even drove 80 miles to check an authorized retailer of one of the devices.
there are several devices out there claiming boosting cellular signals to improve communications. the more credible devices have two antennas operating on a master slave fashion. the master is suppose to be located as high as possible where you have the strongest signal ( which for me is third of a bar where my street mailbox is! my neighbors will love a tall poll with an antenna right there LOL); some brands need the master antenna to be oriented to the closest known tower ( i have not found reliable information on where att towers are location; matter of national security LOL ); on all of them, the distance between the master and slave antenna is critical, most specs call for around 30 ft, the few customer reviews i read time ago talked about longer distances else the interference between the two antennas makes the system useless which is clearly spelled out on the manuals; there is a brainy box where both antennas connect; then there are spatial considerations, vertical or horizontal distances between antenna and box
the catch indeed is in the distance between the antennas; the systems ship with cables for both antennas that may not fit your length needs, mostly are longer than you think; joining extra cables is not really good, adds attenuation to your signal, so here comes the extra cash for a one-piece longer cable.
to their credibility, the majority of satisfied customers live in urban areas where there is good signal but poor reception due to surrounding taller buildings. placing the master antenna on their roofs solves the problems. on rural areas, like where i live, it really boils down to towers. my son's phone carrier is verizon and he gets enough signal to use it. his prior carrier was the old alltel and we had good enough signal too.
i figure that att will spend money to provide 3G coverage to current serviced areas than expand the rural tower situation.
after my research i still did not want to go and spend $500 to try to see if it worked. by the time you get your money back after returning the device... you have an ulcer. still love my iPhone and will not change it for anything.. when i'm home i can still use my land phone. One day other carrier may be added to the iphone list of providers and all be good.
