Affordable mobile digital amateur radio communication

The Digital Mobile Radio standard was first agreed upon in 2005 by a group of amateur radio manufacturers seeking a solution to the proliferation of incompatible proprietary digital solutions on the market at that time. The lack of standards and interoperability had caused the market to fracture, as each manufacturer attempted to postion their digital solution as "the standard" and consumers afraid of placing their bet on a technology which might end up not widely supported, stood on the sidelines waiting for a clear leader to emerge.

DMR was seen as a means to provide an inexpensive, broadly supported framework for digitally interoperable radios using two-slot time division multiple access (TDMA) in a 12.5 kHz channel.

Once ratified (and subsequently managed by an industry funded independent organization), DMR has been recognized by the European Telecommunications Union and published as a standard. While DMR continued to make inroads into the amateur radio market, proprietary standards continued to own considerable market share, especially for business use, where interoperability is not essential.

ARPSC Joins the Digital Age

By 2015, with the Amateur market still largely split among multiple standards, ARPSC leadership undertook the task to evaluate a number of digital technologies available to the Amateur community. After considerable research, real world tests and equipment assessment, ARPSC chose the DMR platform. Initially temporarily deployed in support of the 2016 Brooksie Way, DMR was found to be well suited for the organization. As such, with the support of Oakland County, the existing analog UHF repeater was retired and on February 1, 2017 the new ARPSC DMR repeater was placed into service.

One of the key criteria for the selection of DMR was the availability of economical equipment that the ARPSC volunteers would need to acquire. As such, the ARPSC DMR repeater is compatible with competitively priced DMR Tier II radios such as the TYT MD-380 from Tytera, Connect Systems CS-800 mobile rig, and HT's by a number of manufacturers.

Note that some radios (including the Baofeng GT-3 DMR Mark IV Two Way Radio) although marketed as "DMR Compatible" are actually Tier I radios and are not fully compatible with the two time-slot, Tier II technology in use across Michigan and at ARPSC. Although this sounds obscure, if you are in the market for a radio to be compatible with the ARPSC repeater, be sure to look for radios complying with digital protocol ETSI TS102 361-1.-2.-3.

Oakland County ARPSC DMR Channels

Tag Frequency Offset Color Code Slot TGID
63ARPSC1 444.4625 +5 MHzOffset 1 1 8901
63ARPSC2 444.4625 +5 MHzOffset 1 2 8902
63SMPXD1 445.5125 Simplex 2 1 8911
63SMPXD2 446.6375 Simplex 2 1 8912

DMR has become a great tool for ARPSC activations as it leaves the VHF repeater available for the amateur community or emergency operations, while DMR in the UHF band provides two separate channels to support the activity at hand. Typically one channel is used in a directed net format, while the other can serve as either support, emergency operations, or routine non-emergency amateur use. For ARPSC activations such as the Woodward Dream Cruise, the Berkeley Parade of Cars, and the annual Brooksie Way half-marathon, DMR provides more capability, marginally better reception than traditional FM UHF, and requires less disruption to the community than dedicating the county-wide VHF repeater to an activity.

Find out more about DMR

The following videos are helpful in understanding and using DMR and MD-380