A radio modem is a device which transmits data wirelessly over a multipoint link or just a point to point link. These devices are not used readily by the general public, but rather used across by law enforcement, military and emergency response agencies. In a radio modem, there is no associated network such as a mobile or satellite network and as such, there is charge or cost associated with data transfer between different modems. A radio modem can usually transfer data between a range of 15 to 50 Km. The type and number of obstructions between two radio modems play a crucial role in the range of these devices. A range of 15 to 50 m would be possible with as minimal obstruction as possible with almost clear line of sight. In case of radio modems being used in a densely populated city, the range can drop down to as low as 10Km. The range however can be boosted with the aid of signal boosters to as high as 100 Km. In terms of frequency bands, radio modems which operate on the licens...