18-SEP-2021: DMR and D-STAR


The impact of COVID slowed trips to the mountaintop repeater sites over the last 8 months, but things are slowly getting back to the new normal for the TECHTEAM. The efforts over the past 2 years to upgrade the analog repeaters at every site have really paid off for the System. Repeater replacements and site rebuilds have significantly improved the reliability of the sites to the point where most trips to the hilltop are driven by preventative maintenance schedules. With the analog system in good condition, our attention now turns towards DMR and D-STAR.

The vast majority of the PAPASYS DMR repeaters are the current generation Motorola SLR-5700 model. These repeaters are rock solid with excellent receivers and transmitters that can put out 50W continuous 24/7. We’ve been able to install this modern hardware because of the participation of the membership in various fundraising activities and the generous direct contributions made by members specifically to strengthen our technical foundation.

These new DMR repeaters take up less space in the equipment rack, run dramatically cooler (critical for long-term operations), put out more RF power, and have better receivers than the legacy DMR repeaters. As a big bonus, they come with a 5-year warranty making this a solid investment in the future of the club. We have four DMR sites to go for future upgrade to the Motorola SLR-5700. If you can help get us there faster with a contribution, please contact Cecil.

Speaking of upgrades, we are beginning to upgrade the D-STAR infrastructure as well. To date, all of the D-STAR repeaters (with the exception of one) have consisted of hardware manufactured by ICOM in the early 2000’s. At that time, they represented the only equipment available to implement a D-STAR repeater. Unfortunately, these repeaters were not well suited for the harsh RF conditions found on mountaintop repeater sites in Southern California. Significant external filtering was required to protect the receiver and the transmitter output was an anemic 10W.

The exception noted above was located at the PAPA9 site. This repeater was an early effort by Jim McLaughlin, KI6ZUM, to integrate his new multi-mode digital voice modem (MMDVM) with a conventional analog voice repeater to transform it into a D-STAR repeater. This effort proved to work well and is still installed as D9 on the system.

Recently, we have seen the nearly 20 year old ICOM repeaters begin to fail. As the spares where quickly exhausted, we looked toward the D9 experiment as the solution. Building on the success of the DMR repeater upgrades to the Motorola SLR-5700, we integrated a modern version of the ZUM Radio MMDVM modem with the SLR-5700 repeater. The first repeater was installed at Santiago Peak (D3) two weeks ago as a replacement for the old ICOM system. The performance of the new D-STAR repeater is well beyond expectations.

With the Edom Hill D-STAR repeater experiencing problems (D16), a second Motorola SLR-5700 D-STAR repeater was constructed and installed this week. Again, the results have been outstanding. We hope to continue to upgrade the performance of the remaining D-STAR sites with this same combination in the near term. Thanks to Jim, KI6ZUM, for his continued technical support as the PAPA System upgrades our infrastructure. If you can help with the acquisition of repeaters to move this project forward, please contact Cecil. The D-STAR repeater callsigns for Santiago Peak and Edom Hill have changed recently. Please check the website for the latest information required to properly program your equipment.

Behind the scenes on DMR there have also been some recent changes. As you probably know, the PAPA System is connected to the BrandMeister network. BrandMeister has implemented some new security features that have required the TECHTEAM to visit many of the sites to reconfigure certain operating parameters in the repeaters. This process is nearly done. The conversion has not been without problems however. We have been experiencing intermittent BrandMeister network interruptions over the past few weeks. Occasionally, these service interruptions have been a result of issues with our microwave interconnection backbone. Most, however, have been related to issues with BrandMeister as the network implements its new policies. We are continuing to update our DMR sites and are closely monitoring the BrandMeister network as we work through these service outages.

Recently, some new hardware was installed at Toro Peak to help us diagnose problems with the utility service at the site. There is no commercial AC power at the site. AC power is supplied by a fulltime generator farm at the site. Throughout this past summer, we have experienced numerous outages relating to generator or fuel issues. The generator plant is maintained by the site owner and just getting to the site can take hours from any of the nearby communities. Often, when power would go out, we were not aware of the issue because our rack would seamlessly switch to our backup battery system. Only when the battery was exhausted would we know that there was a problem. To remedy this, we installed a sophisticated automated site monitor in our rack that is connected to our Internet backbone. Now, when the primary AC power fails, both PAPA and the site owners are notified by email of the condition. This should improve response time and the availability of site for the membership.

As winter approaches, the TECHTEAM will visit the sites that typically become inaccessible during the season due to snow and ice. Inspection of antennas, feedline, and weatherproofing are prioritized before the snow keeps us away.

While the mountaintop visits are high profile events, the TECHTEAM is constantly working behind the scenes to maintain and improve the network that keeps us all connected. I want to thank WD8CIK, K4DDU, AF6FB, WD6FZA, N6JVH, W6SAT, KB6THO, K6UHF, and the many other volunteers who give generously of their time and expertise to keep the PAPA System running smooth for the membership.


Author: Chris AA4CD

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