Well Rx1 Rssi values for both 2766 and 598u were almost same, i checked it on the same spot also on roof. Even if the modem moves slight a bit there is vast amount of drop in speed. This problem was with both modems. I am not sure whether to call it worthy or not just yet. Anyway i don't see the need for me buying an external antenna, i don't think there will be any improvement in speed, its just too much of a risk, antenna costs about 1k cheapest i found on ebay which looks like toy. The real antenna which i think would definitely improve my speed is patch antenna, those are installed on the rooftop facing the network tower which costs about 3 to 4k, i am certain and absolutely sure that my connection speed will improve with this sort of antenna but i just can't spend this much on an antenna. I have talked to many bsnl evdo users whom used to get 1x in at their home, but after installing patch antanna they are receiving full evdo signal with 2+ mbps constant speed. My signal values varies between 75-110 dbm. If yours is truly near around 60 dbm(you must be pretty close to the tower) then i am certain that 598u will definitely boost ur connection performance. I cannot say which is better at the moment, but sierra 598u has external antenna port that makes it above ac2766.