Usually the current antennas used on your current USB modem are extremely small and provide low signal so adding one of these with a 3G antenna will boost your signal greatly.
SMA to Induction 3G Plug | 510mm | AR-3330 |
SMA Adaptor To HUAWEI E160/618 Plug | 500mm | AR-3332 |
SMA Adaptor To SIERRA TS9 Plug | 500mm | AR-3334 |
SMA Adaptor To TELSTRA 4G USB Modem Lead | 490mm | AR-3336 |
Low Loss SMA Extension Lead | 5m | WC-7824 |