BridgeCom Systems D-500 70 cm DMR and Analog Handheld Transceiver by QST March 30, 2017 08:00
Reviewed by Pascal Villeneuve, VA2PV
In the past few years, VHF/UHF digital voice communication has been one of the fastest growing segments of Amateur Radio. D-STAR and System Fusion (C4FM) were specifically designed for Amateur Radio, but this is not the case with DMR — Digital Mobile Radio. It is an open standard, developed by the European Telecommunications Standards Institute (ETSI). As such, this technology is available to any company willing to build a digital radio, such as the BridgeCom Systems D-500 (by TEKK) reviewed this month. Introduction to DMR There are three types of DMR — Tier I, Tier II, and Tier III. To learn more about DMR, I strongly suggest that you read “Introduction to Digital Mobile Radio (DMR)” by John S. Burningham, W2XAB, in the October 2015 issue of QST. In this review, we will concentrate on the widespread Tier II DMR network. You will need to understand a bit about this technology to program your DMR radio. As DMR was not developed specifically for Amateur Radio, the terms are different from what we are used to. Tier II DMR uses TDMA (Time Division Multiple Access), which is a frequency-sharing protocol. You can have two conversations on the same frequency without interfering with each other. This is very efficient, as Tier II TDMA uses a 12.5 kHz bandwidth with two time slots. The switching is very fast, thus allowing for two simultaneous contacts on the same frequency, using this time-sharing method.