History of SCHEART DMR

Occasionally a group of people come together and create something for others to enjoy.  It doesn’t happen often, but when it does the results can be very rewarding.  This is the story of the SCHEART DMR network and the many people who made it happen.  It is based on stories from the creators and attempts to document the evolution of the network.

The Beginning

On October 25, 2013 a group of Columbia amateur radio operators were sharing lunch at the Flight Deck Restaurant in Lexington, South Carolina.  It was just a group of operators that occasionally had lunch and enjoyed fellowship. 

Steve Davis, N4UHF started a conversation about current field testing of a new Motorola Digital Mobile Radio (DMR) repeater in the commercial market and that the initial test results were surprising good.  There was a general discussion about digital structure of the Motorola implementation of the DMR standard.  Several of the operators had been experimenting with DSTAR for a few years and expressed an interested in the DMR technology.  Roger Mull, KD4JQJ suggested that those interested should put up a DMR repeater in Columbia and test out the new technology.   That generated discussion on a location for the repeater and the cost for individual radios.   It was suggested a repeater placed at Little Mountain, South Carolina would provide for wide coverage and should be a suitable test site.  The group would need to see if SCE&G or SCETV would allow an installation, determine if a frequency pair would coordinate, and then determine the costs involved for the repeater and radios.   Steve and Roger agreed to work the details.  At this point about 10 people expressed interest in the project.

After the lunch Roger approached John Crockett, W3KH Manager of Transmission for SCETV about testing a DMR repeater at their microwave facility on Little Mountain.  A little background about John.  He obtained his radio license at an early age and was passionate about ham radio.  John had spent a tour in Vietnam doing airborne communications.  After leaving the service, John attended North Carolina State University where he was involved with the club station and local repeaters. He also met and became close friends with Danny Hampton, K4ITL who will appear again later in this story.  John had a couple of jobs before joining SCETV first as a field engineer and by 2013 was the chief engineer involved in the design and installation of a statewide amateur analog repeater network we know as SCHEART.   John was a mild-mannered guy who had a wealth of information about RF and repeaters.   

Since DMR represented new commercial grade technology which offered a robust simultaneous 2 channel capability on a single frequency pair, John quickly endorsed the project and offered to host the test location.  Additionally, SCETV would supply the antenna and feedline for the project.  John offered to join the group and help purchase the equipment and conduct tests of the technology.

Timing can be very critical in this type of an endeavor.   Motorola was offering a special promotion on DMR radios.  Customers who purchased 10 or more radios and returned a radio for each one purchased would receive a discount of about $100 per radio.  The promotion was effective until the end of December.  So the test group needed to find enough people to purchase 10 radios and then enough people willing to buy the repeater.  By October 31, the following individuals expressed interest in buying a new Motorola DMR radio:  Steve Davis, N4UHF; Gary Lennert, K2KYJ; John Crocket, W3KH; Boykin Roseborough, N2CP; Roger Mull, KD4JQJ; Susan Benesh, KK4DGM; Gene Retske, W4DSN; John Perriero K4WIC.

Steve’s company offered to purchased 4 radios and two members of the group expressed interest in getting a mobile and HT radio which would exceed the 10-unit promotional threshold.   Now the challenge was to get the group to reach an agreement on going VHF or UHF. Within the group there were strong support for both bands.  Getting hams to agree to a radio, a band or a mode can be a real challenge. The fact that UHF radios were $50 to $100 more placed a big handicap on the UHF supporters.  By November 6, the group agreed to pursue a VHF frequency pair and get more solid cost figures for the radio and repeater.

The next major milestone was obtaining a coordinated frequency pair.  Most hams will never need to coordinate a repeater frequency pair.  However, for those who want to operate a repeater, you need to find a free pair and apply for a coordination of the frequency pair.  In order to maintain order and allow repeaters to work together the FCC recognizes various organizations who check distances between repeaters and use good engineering practices to coordinate pairs to minimize interference.  The coordinating body for the southeast is SERA, the Southeastern Repeater Association.  In 2013, coordination process was still paper based and could take some time to process a request.  Steve submitted the group’s request for 145.480 MHz/144.880 MHz pair on November 23 after determining the pair should coordinate at the Little Mountain location running the planned effective radiated power. 

During the process of finding a pair, the group sought investors to fund the purchase the repeater.  Out of the group, six individuals offered to purchase the repeater and radio programming software.  Costs would be split 6 ways.  Once installed everyone with a radio would be free to use the repeater. 

Within a few of days of the coordination application, the group received feedback from SERA that indicated the frequency pair was going to be a problem.  SERA was in process of developing new policies for all digital repeaters and had placed a moratorium on all digital coordination on 2-meters.  No policy decision was planned until after the SERA board meet in January 2014.  However, obtaining a 440 MHz coordination would be possible.  New plans and costs estimates had to be developed for the UHF band if a repeater was going up in 2013.  Another group discussion and it was agreed to go with a UHF repeater.  Steve worked with the vendor to obtain updated radio costs and Roger worked to get a firm commitment for investors in purchasing a UHF repeater.  By December 6, Steve had firm prices from a Motorola vendor in Charleston on the radios, repeater, programming software and cables.  At this time one of the original 6 repeater investors determined the added cost of UHF was too much and decided to drop out.  After coming this close, the project was in real trouble of failing.  After a series of telephone discussions, Gary, K2KYJ and Roger, KD4JQJ agreed to purchase the 6th share between themselves along with their original share.  The project was back on.

The equipment arrived on December 30th and Steve, N4UHF delivered the equipment to Roger, KD4JQJ on December 31 for programming.  John, W3KH, suggested that Roger contact Danny Hampton, K4ITL, to get pointers on programming the equipment.  As indicated previously, John and Danny had been friends since his days at NC State and Danny was leading an effort to deploy a statewide DMR network in North Carolina.  When Roger contacted Danny, he was extremely helpful and explained their PRN radio network being installed across North Carolina, Virginia and Tennessee.  He offered to let the new Little Mountain repeater join the PRN network and have access to talk groups outside the state.  At this point the group still didn’t have a coordinated UHF frequency pair. However, Danny was able to obtain and coordinate a pair from SERA within 24 hours (443.5375/448.5375 MHz).  It certainly helped that both John and Danny were Directors in the SERA organization for their respective states.  Danny put Roger in touch with Scott Whitaker, KF4DBW, who managed the PRN C-Bridge network switch.  Things moved extremely fast at this point.  On January 1st, the first radio id’s from DMR-MARC.net were obtained.  At the time DMR-MARC  (Motorola Amateur Radio Club) supported the World Wide registrations of all amateur DMR repeaters and users.  They also controlled various talk groups like Worldwide, North America and one for every state.  Applying for the ID’s was painless, and it took less than 30 minutes to receive an ID for a radio.   Once ID’s were received, new code plugs were loaded into the Motorola XPR8440 repeater and XPR2500 radio.  Within one minute of plugging the repeater into a Network, the repeater was linked to the PRN C-bridge. While working on the test bench into a dummy load, it was possible to have conversations with stations across North Carolina.  John provided a used UHF duplexer which Roger tuned to the assigned frequency pair.  For about week, bench tests were conducted before the repeater was installed at the site.   On January 9, 2014, John and Roger installed the repeater at the SCETV facility at Little Mountain.  This DMR repeater was used as a a proof of concept for the future SCHEART digital network expansion.    Field tests were conducted during January to March comparing coverage to 2-meter analog, digital error correction and ability to have multiple conversations on different talk groups.  Based on previous experience with the DSTAR system, an engineering analysis determined DMR had superior error correction and packet recovery.  DMR provided 100% copy with receive signal strength levels at -122 dBm and 90% copy at -123 dBm.  At similar levels, DSTAR would have excessive R2D2 artifacts making conversations very difficult.   Comparing DMR to analog signals which have 100% copy around -115 dBm and 90% at -117 dBm from a moving vehicle, it appeared the DMR digital signal provided about a 3 to 5 dBm improvement on audio recovery.  Real world coverage appeared very similar to a 2-meter analog signal while operating at 440 Mhz.  These benefits plus radio alerts and radio to radio text messages made DMR a very flexible communication technology. 

 SCHEART- A Short History

In the early 2000’s a group of amateur operators, engineers and healthcare specialists had come up with a plan to link the hospitals in the Charleston area via Amateur Radio.  This system provided an emergency back up communication channel should an earthquake or other natural disaster damage the primary communication network.  Medical University of South Carolina  emergency management was heavily involved and the project worked so well, the concept was pitched to the South Carolina Hospitals Association (SCHA) and Department of Health and Environment Control (DHEC).  Since SCETV had existing towers across the state connected to a microwave network and extensive RF engineering experience, they were invited to discuss development of a statewide network to support auxiliary communications. During discussions of the need to  have redundant communications to support hospitals, county emergency operations centers were added.  John agreed to assume the role of Chief Engineer for the SCHEART analog network if SCETV would own the network and manage it as part of their state emergency support function.   To fund the project, grant money from the US Department of Health and Human Service (USDHSS) was obtained with support from DHEC and SCHA. 

As envisioned, a VHF/UHF network of repeaters would provide hospitals and county government access to a configurable statewide amateur radio auxiliary communications system that would be available during emergencies.  During non-emergencies, the network work would be open to any licensed amateur for use.   While providing superior regional coverage due to antenna heights, during emergencies most traffic on the network would be restricted for statewide communication, limiting availability to local traffic.  With that analog system, there wasn’t a way to have separate statewide and local traffic on the same repeater.  But with a DMR network, both local and statewide traffic could occur without interference.  John and Roger began discussing how a statewide DMR network could be used to support command and control traffic statewide and provide for a separate talk group for local command traffic.  Much of the supporting infrastructure was already in place.  The preliminary estimate for a statewide Motroturbo based network was about the cost of 20 portable public safety radios.  At the same time, the network would provide the latest commercial quality system and allow future enhancements.

The Digital Big Bang

John discussed the concept of a new digital network with representatives of SCEMD and SLED to seek their support.  Grant applications from the Department of Homeland Security (DHS)  funding were prepared and by May, 2014 the first grant was approved.  During the same month, Matthew Littleton, KN4SWB, with Anderson Sheriff’s Department had used local grant money to purchase a DMR repeater and 18 radios for his county.  Matthew tested their  repeater connected via satellite back to the Conference server located in North Carolina and had a conversation with Roger, KD4JQJ on the Little Mountain DMR.  The successful test opened new opportunities for using DMR in support of incident command during an emergency.

By July, Phase 1 installation of DMR repeaters was underway.  SCHEART volunteers Gary, K2KYJ and Roger, KD4JQJ programmed the DMR repeaters, tuned the duplexers and installed the rack of equipment at SCETV sites.  On many site installations, John participated.  SCETV personnel performed all tower work.  By the September 25, 2014 program review at SCEMD, SCHEART reported significant progress.  The Charleston-South (Whitehall) repeater was providing mobile coverage from Georgia state line on I-95 to the I-26/I-95 intersection.  The Greenville (Caesar’s Head) provided mobile coverage from NC border to I-85 at Commerce Ga and to I-26/I-385 intersection.  This site was operating stand-alone pending a network connection.   The Dillon repeater, which is installed on the WPDE tower at 1500’, covered well into NC and NE South Carolina.  The Charleston-Wallace with an antenna at 300 feet provided HT coverage downtown.  The Walhalla repeater located at Long Mountain was providing great coverage in western SC but was operating stand-alone awaiting an Internet connection. The Walhalla repeater was part of the developing SCHEART network but not purchase under the DHS grant.  The South Carolina C-bridge was being configured which would allow all the SCHEART-SCETV DMR repeaters to be connected inside the agency firewire.  Thus loss of the Internet network connections would not impact the DMR repeaters.

By December 2014, phase 1 was moving rapidly.  Additional repeaters were installed at Charleston-North (Awendaw), Conway, and Florence.  The South Carolina Conference Bridge was ready for accepting repeaters thanks to Steven Hester, N2PQ, Scott Whittaker, KF4DBW, Shaun Bennett, AJ4DI,  and Roger, KD4JQJ.  Cutover of repeaters to the new bridge was underway.

Phase 1 DMR installation was completed in May 2015.  The South Carolina Conference bridge was operating with a redundant back up.  It had been configured to operate normally with the North Carolina bridge allowing multi-state communication but during emergencies it could be isolated and operate only within South Carolina.  The following repeaters were connected and operational: Columbia (East &West), Charleston (North, South & Downtown), Greenville, Myrtle Beach, Sumter, Greenwood, and Florence.  Additionally, portable repeaters were installed in the SCHEART trailer, Aiken County trailer and Anderson County trailer to support mobile operators.  Including the Walhalla partner repeater, the system supported 15 repeaters, 3 of which could be linked via satellite.  May also started off phase 2 of the project funding.

Around this same time, John discovered he had esophageal cancer.  The SCHEART program and the DMR installation were secondary to his primary job of Vice President of Engineering for SCETV.  However, he continued to drive the program while undergoing cancer treatments and tests.  Being an engineer, John tried to approach cancer with logic and positive energy.  He had a deep love of amateur radio and concern about providing support to the citizens during emergencies.  John really wanted to complete the DMR project along with the last parts of the analog network.  While he continued to manage the program and paperwork, volunteers programmed and install repeaters as they arrived.  On his good days, John would go with them to oversee the installation. 

Motorola came out with the SLR5700 line of repeaters in the spring of 2015.  The design was more robust than the XPR8400 repeater and had more remote monitor features.  It was decided to move to the SLR5700 as SCHEART standard and to install them at all TV transmitter locations.  This required swamping out the older XPR8400 repeaters and moving them to lower RF locations such as microwave site. By the end of 2015, additional DMR repeaters were added at Rock Hill, Spartanburg, Columbia Downtown, Lake City, Barnwell, Beech Island, and Orangeburg.  Both Charleston Downtown and Columbia Downtown repeaters were added to support HT coverage and building penetration for emergency communications.  They were added to the list of target sites after tests inside buildings provide problematic.

During 2016, John’s health continued to deteriorate.  While he wasn’t able to go to work on many days, he kept in touch with the volunteers working on the DMR program and ensured they had the parts need for the installations.  John was unable to go to the Lake City installation and Roger,  along with Gene Retske, W4DSN performed the installation and integration.  By October, John was hospitalized and lost his battle against cancer.  It was a major blow to the amateur radio community and SCETV.

However, the volunteers and dedicated SCETV personnel continued with the program and additional DMR sites were installed at St George, Beaufort, and Georgetown.  George Mudd, KK4F took the lead installation of the Sumter Downtown repeater at Toumey Hospital.   Amateurs at Hilton Head also installed a repeater on the island and one at Bluffton.  Eddie King, N4HEK was the driving force to integrate their repeaters into the SCHEART network.  By January, 2017 all planned SCHEART DMR repeaters were operational and the system network supported two hurricanes/floods.  DHS grant funding supported the installation of 23 repeaters, and 8 combiners and the conference bridge. Combiners were used where the DMR could share the UHF analog antenna and save the cost of installing new antennas.

Two more non SCHEART repeaters joined the network in 2017.  Pickens added a repeater at Glassy Mountain and Mandell Rigdon, WR4XM was the lead to integrate it with SCHEART.  Alex Norwood, K4BAN integrated a repeater at Clemson into the network.  This brought the network to 28 repeaters within the state.  During non-emergencies, one DMR talk group connected to 60+ repeaters across 3 states.

January 2018 brought the Anderson repeater into the network.  Richard Donald, N4LRD, integrated that repeater into the SCHEART network.   By mid-year, Chester County Emergency Management expressed the need to have a DMR repeater to improve coverage.   The county worked with DHEC and obtained a grant funding for SCETV to install a repeater on the ETV tower at the High School.  That site was completed in June. 

The original DMR plan called for a gap filler repeater near Cheraw.  Network connectivity had been a issue which precluded the installation.  During 2018 there were discussions on addressing this gap.  An engineering site analysis was conducted in December with a state site identified as the best location.  Funding for the DMR repeater has been obtain from the SCHEART, Inc., a not-for-profit group established after John’s passing to support enhancements to the SCHEART system.  Installation is pending SCETV availability to provide network connection from to their microwave system near Florence.  Due to FCC repack that project was placed on hold but it is still on the books.

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