Digital radio principle

The basic principle of digital 2 way radio is first the analog voice converted into digital signals, then modulation to rf go up. Since the launch of the digital signals, of course, this machine also can be directly transmit data. The appearance of digital radio is also in order to save the radio spectrum, so the current digital radio is mostly a voice channel equivalent occupy 6.25 kHzk bandwidth, namely than general analog interphone save half frequency.
Different digital radio is the practice of different standards. ICOM digital radios used by the dPMR formats and the United States do the old version of the type that used frequency division way (FDMA), a 12.5 kHz from frequency to two bandwidth for 6.25 kHz channel, and Europe and the United States do DMR system is adopted the new version of time (TDMA) way (MOTOROLA and shenzhen sea can reach and other production such products), a 12.5 kHz channel from the time is divided into two cross time piece, the transmit a channel. The latter has more advantages, such as a repeater can also relay two channel, and such as general interphone press PTT others cannot put it after stopped, and TDMA systems on the press PTT is really after the launch of the intermittent, in particular in an emergency, can takes up time out of A B channel and signaling, forcibly shut off the radio signal emission occupy A.