T8D07

SIGNALS AND EMISSIONS · Non-voice and digital communications: image signals and definition of NTSC, CW, packet radio, PSK, APRS, error detection and correction, amateur radio networking, DMR, WSJT modes, Broadband-Hamnet

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Which of the following describes DMR?

AA technique for time-multiplexing two digital voice signals on a single 12.5 kHz repeater channel
BAn automatic position tracking mode for FM mobiles communicating through repeaters
CAn automatic computer logging technique for hands-off logging when communicating while operating a vehicle
DA digital technique for transmitting on two repeater inputs simultaneously for automatic error correction

Why DMR (Digital Mobile Radio) uses TDMA, time-division multiple access, splitting a 12.5 kHz channel into two alternating time slots so two separate digital voice conversations share the same frequency pair at once. Each radio transmits in short bursts during its assigned slot, which also saves battery since the transmitter is off half the time. The commercial land-mobile roots of DMR are why the 12.5 kHz channel spacing shows up in the definition.

Watch out The automatic position tracking description belongs to APRS, not DMR; DMR is a voice mode, and nothing in it involves transmitting on two repeater inputs at once.

DMR = Two slots, one 12.5 kHz channel. Remember the pair: TDMA and 12.5.

HamSandwich explanation, first draft. The question and answers are the NCVEC text.

T8D07

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