Digital Mobile Radio Repeater in West Seattle
The West Seattle Amateur Radio Club is in the process of establishing a Digital Mobile Radio Repeater in West Seattle, and that:
1) it has accepted the offer of Seattle ACS and the City of Seattle to co-locate the new DMR repeater at the SDOT Westcrest Tower, and that;
2) the new WSARC DMR repeater will be connected to the SeattleDMR.org network, and that;
3) a member of the WSARC Board will be designated as liaison with SeattleDMR.org
Background on Digital Mobile Radio Standard
Digital Mobile Radio (DMR) is based on an open standard published by the European Telecommunications Standards Institute (ETSI). TS 102 631 parts 1-4. The primary goal of the ETSI standard is to specify a digital system with low complexity, low cost and interoperability across brands, so radio communications purchasers are not locked into a proprietary solution. One of the benefits of DMR is that each repeater can support two simultaneous conversations via two time slots, and that many talkgroups can be supported, logically isolating groups of people into conversations or geographies.
DMR is utilized for business radio communications across Europe and in North America. This has driven manufacturers to very high volume/low cost production of radios. You’ll frequently see DMR radios used by security guards, event hotels, venues, small local governments, and construction.
In contrast, Amateur Radio specific digital radio technologies were developed and driven by Japanese amateur radio manufacturers for the Amateur radio markets in Japan, North America and Europe. This is a much smaller market, so R&D costs are spread over fewer units produced, and manufacturing is at a smaller scale than for DMR, having lower efficiency. This translates to higher unit costs for radios. For example, a very good dual-band DMR/FM portable radio (Anytone D878UV) sells for $220-$240. In contrast a Yaesu dual-band Fusion/FM portable radio (FT2DR) sells for $345, and the new FT-3DR sells for $450. An Icom dual-band D-Star/FM portable (ID-51A Plus) $340.
DMR Linking and DMR Repeater Groups
Inherent in the DMR specifications is the capability for repeater linking via Internet Protocols (IP). A variety of DMR Repeater Groups have built DMR repeater networks across the US and indeed the world. There are two methods of linking – A system called C-Bridge System, or competing system called Brandmeister.
Here in Washington, Oregon and Idaho we have the Pacific Northwest DMR network. The network consists of primarily privately-owned repeaters and covers an impressive geography and most of our freeways in Washington.
In Oregon the DMR repeater network is an affiliate which is effectively owned by one ham and is dedicated to supporting Search and Rescue. That ham sets the policies for his network, such as a limit on QSOs to 15 minutes.
Repeater groups in California are always a good place to observe chaos and controversy.
At this point, about half of the repeater groups in California have embraced Brandmeister, and about half are still favoring the c-bridge systems. There is some co-mingling between systems which allows state-wide communications
Seattle DMR Bridge:
In 2018 the Puget Sound Repeater Group (PSRG) approached PNW Digital to request a Talkgroup Assignment for Seattle. After many e-mails and much dialog we learned that PNW digital was not an organization with a board, but was in fact a loosely affiliated group of individuals with just one person setting the policy. That person was not amenable to a Seattle specific talkgroup being created, or the bridging of Brandmeister talkgroups and felt that our needs could be handled by the existing state wide talkgroups.
PSRG put their DMR repeater on the air at Capitol Park. Doug Kingston, KD7DK, built a DMR Bridge Server using open-source software and connected the PSRG repeater to both PNW Digital’s MMDVM/C-Bridge System, and to Brandmeister. The Seattle DMR Bridge was established.
Seattle ACS deployed a DMR repeater at Lake Forest Park in North Seattle.
The Lake Forest Park DMR repeater is linked to the Seattle DMR Bridge, and carries the same talk groups as PSRG.
WSARC will establish a South Seattle DMR repeater and have that repeater linked to the Seattle DMR Bridge. The South, Central and North repeaters would provide city-wide radio coverage, supporting Seattle 1, Seattle 2 talkgroups and a selection of talkgroups as requested by members.
SeattleDMR.org is intended to be a co-operative association which enables mutual assistance between Greater Seattle area radio with the goal of facilitating “Roaming” across club repeaters for greater range, and to provide connectivity to other DMR networks elsewhere.
It is intended that SeattleDMR.org would not engage individual amateur operators as members, nor would it operate repeaters itself. Seattle DMR would operate as a co-operative among existing clubs, supporting and enabling a roaming network via the Seattle DMR Bridge.
SeattleDMR.org would operate democratically with each member club having influence in operation of the co-operative.
Private repeater owners may connect their repeater to the SeattleDMR.org bridge, and may extend the roaming network coverage reciprocally, however private repeater owners would not be eligible for membership in SeattleDMR.org, nor participation in the direction of SeattleDMR.org.
It is proposed that the Charter Members of SeattleDMR.org be:
-Puget Sound Repeater Group (Seattle Central DMR repeater at Capitol Park)
-Seattle Auxiliary Communications Services. (Seattle North DMR repeater at Lake Forest Park)
-West Seattle Amateur Radio Club (Seattle South DMR repeater at Westcrest Park)
DMR Repeaters for EmComm:
It is envisioned that the city-wide coverage of 3 SeattleDMR.org member repeaters will be attractive to Seattle ACS and may form part of the Seattle ACS communications strategy for emergencies.
WSARC at the forefront of Digital:
PSRG, Seattle ACS and WSARC are partners in a joint Field Day, and many WSARC members are also Seattle ACS Members and PSRG members. This cooperative project enhances value for a broad base of membership and better serves our local and regional communities.
Internet connectivity at Westcrest for the DMR repeater will be provided by a HamWAN Dish & Radio which will be linked to the HamWAN Puget Sound Data Ring, which has cells deployed at numerous wide-coverage sites. These sites are interconnected with 5 GHz modems and routed with OSPF, forming a redundant high-speed backbone to route traffic between sites and to the internet.
Written by Randy W3RWN
The DMR repeater was approved by the WSARC Board of Directors in August 2019.