Metrocrest Amateur Radio Society
Hands-On
February 1, 2022
Dallas County Medical Reserve Corps Part 90 Project
—Kevin Grantham N5KRG
The Dallas County Medical Reserve Corps asked me to help create a transportable radio system for use by volunteers and others at incident and event sites. The initial procurement was funded by a FEMA grant in October 2020. In March, 2021, the MRC and I began work on proposals.
Working with the stakeholders and examining the use cases, I proposed a Part 90 public safety band UHF system. The reasons are:
1) The experience with the COVID-19 vaccination sites showed that radio communications were a necessity.
2) There are not enough licensed amateur radio operators to properly staff sites for a long-term (weeks, months, years).
3) Non-licensed people cannot use amateur radio frequencies, and most of the volunteers and staff will be unlicensed.
4) HTs are of limited use in and around buildings.
5) The County is moving towards a P25 system being implemented by the Texas Department of Public Safety and acquired by the City of Dallas Office of Emergency Management under a Department of Homeland Security grant. It’s a Motorola system and the lowest-priced handsets are $1500 each. The MRC doesn’t have the budget to pay for very many of those.
The proposed Part 90 design includes eighteen (18) VHF/UHF HTs and four (4) VHF/UHF mobile units. The mobile units will be mounted in surplus hard cases previously acquired for the Point of Dispensing (POD) site amateur radio kits (Kenwood TM-D700 with power supply, laptop running Winlink, antenna and accessories). The County had sixty POD kits but had never used more than 37.
I helped the County acquire a pair of 460MHz frequencies in the Public Safety – Health service and chose AnyTone® AT-878UV II HTs and AT-578 UV II Pro mobile units. These are FCC Part 90 approved radios that will also operate in the amateur radio service should that be desirable in the future. They will be programmed as Part 90 devices—no front panel frequency entry.
Also, a Hytera and a Motorola repeater unit were identified and presented. While not in the current budget or project, the license includes a portable repeater so if that’s approved and acquired it will enhance their capabilities.
In June we sent the proposal to the Commissioner’s Court and was approved by September. Orders were written and the equipment arrived in early December. Due to the vaccination sites taking most of the County’s HHS resources, we couldn’t work on the radios until the last week of December.
To date, all HTs have had their firmware upgraded and programmed with simplex analog channels on the Part 90 frequencies. We started reworking the kits and blew up about twenty power supplies whose electrolytic capacitors had either dried out or were counterfeit. We all know that electronics work on smoke and when you let the smoke out, they don’t work. We let out copious amounts of smoke. We finally found four working supplies and built the mobiles into those kits.
Remaining tasks: Upgrade the firmware in the mobiles and push the Part 90 code plug. Both the HTs and the mobiles use the same code plug—a nice benefit of using AnyTone equipment. I am also developing five “ham” zones that can be put into the code plug for RACES, ARES® and SKYWARN® repeaters in each of the five counties participating in this project. Also, their Part 90 license was issued as FM narrow (12.5KHz). I have recommended they request a modification to DMR Tier II to allow them to get twice the capacity (two time slots per frequency) and encryption so that HIPAA-protected information can be communicated over the air, something that is not legal on amateur radio frequencies. Then, the repeater may get approved and we can provision that.
The repeaters proposed are like the Yaesu System Fusion repeaters and the new Icom D-STAR repeaters. They can be set up as analog FM, DMR, or Automatic Mode Switched. They have a built-in duplexer that would be unsuitable for a high-density environment like where most of the MARS club repeaters are located, but perfectly acceptable for mobile operation.
—73 Kevin, N5KRG@ARRL.net