Deep Dive: T8D07
The correct answer is A: A technique for time-multiplexing two digital voice signals on a single 12.5 kHz repeater channel. DMR (Digital Mobile Radio) is a technique for time-multiplexing two digital voice signals on a single 12.5 kHz repeater channel. DMR uses Time Division Multiple Access (TDMA) to divide each 12.5 kHz channel into two time slots, allowing two simultaneous conversations on one frequency. For amateur radio operators, DMR provides efficient spectrum use and features like talkgroups, individual calling, and text messaging. Understanding DMR helps when operating on DMR repeaters and explains how digital systems use spectrum efficiently.
Why Other Answers Are Wrong
Option B: Incorrect. DMR isn't specifically for automatic position tracking on FM mobiles - that's APRS. DMR is a digital voice system with time division. Option C: Incorrect. DMR isn't for automatic computer logging in vehicles - that's a separate function. DMR is a communications protocol, not a logging system. Option D: Incorrect. DMR doesn't transmit on two inputs simultaneously for error correction - it uses time slots on one frequency, not simultaneous transmission on multiple frequencies.
Exam Tip
DMR = time-multiplexing two signals on one channel. Think 'D'MR = 'D'ivide 'M'ultiple 'R'adio signals using time slots. Two conversations share one 12.5 kHz channel using TDMA. Not for position tracking, logging, or dual-frequency transmission.
Memory Aid
DMR = time-multiplexing two signals. Think 'D'MR = 'D'ivide 'M'ultiple 'R'adio signals. Two digital voice signals share one 12.5 kHz channel using time slots (TDMA). Efficient spectrum use.
Real-World Example
A DMR repeater on 145.500 MHz uses time division to carry two conversations simultaneously. Time slot 1 carries one conversation, time slot 2 carries another - both on the same 12.5 kHz channel. This doubles the capacity compared to analog FM, which can only carry one conversation per channel. DMR's time division is what makes it efficient.
Source & Coverage
Question Pool: 2022-2026 Question Pool
Subelement: T8D
Reference: 2022-2026 Question Pool · T8 - Signals and emissions
Key Concepts
Verified Content
Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T8D topic.