We at KS-DMR really like to do things right. We’re all about clean installs and top-quality equipment. Two of our favorite things are the Repeater-Builder STM32-DVM MMDVM Modem and the Motorola MTR2000 repeater.
The MTR2000 is a really awesome package. It packs a lot of purpose-built, public-safety grade repeater into a small amount (just 3U) of rack space. But hanging a cable off of the back to go to a Raspberry PI + PiHat or a separate rack mount server adds to the space and clutter. It’s just not as clean, and there are more wires to snag… more chances for something to go wrong.
The Repeater-Builder STM32-DVM is, we think, the best MMDVM Modem board out there. It includes a powerful micro controller, lots of test points, a well-tested filter design, nice diagnostic LEDs, and a handy ‘clip’ light for easy RX level adjustment.
We’d long talked about trying to stuff the Pi+PiHat STM32-DVM into the MTR2000’s card cage, but there were issues. It really didn’t fit well, mounting was challenging, and the package used more current than Motorola rated for the supply to the card cage. We didn’t want to accept no for an answer, so we decided to come up with an even more elegant solution!
Our solution is a new PCB to plug directly into the card cage, just like a Motorola option board, but incorporating the STM32-DVM design. There is a smaller, more power efficient SBC (single board computer) to handle the MMDVMHost functions, since a Pi is both too big, and uses too much current. The result is the STM32-DVM-MTR2K from WA0EDA.
K0USY Group and WA0EDA Club are sister clubs, K0USY Group is the production arm, and was founded in memory of Jack C. Buffington, K0USY, with WA0EDA Club being the R&D “Skunkworks”, in memory of Rolland D. “Slim” Cummings, WA0EDA.– Cort Buffington, N0MJS on the formation of WA0EDA Club and K0USY Group
We’ve made it through design and testing and are ready to introduce this new accessory board into our network. The board is intended to plug into the Option 1 or 2 slot of the MTR2000. By optimizing the circuit for the MTR2000, the pots were removed, along with a few other unnecessary components – all adjustments are completed with the MTR2000’s internal soft-pots and RSS! And, best of all, a much more power efficient OrangePi Zero is included to run the MMDVMHost software, or PiStar, if that’s your thing.
But we don’t intend to keep this innovation to ourselves. In future this board will be available directly from the developer, K0USY Group’s Cort Buffington (N0MJS). It is possible that the board may be offered through a partnership with Repeater-Builder and Scott Zimmerman, N3XCC. The 2nd prototype PCB and production candidate will be deployed next week, so it will be a short while until boards will be available to the public.
For more information contact Cort Buffington, N0MJS, at firstname.lastname@example.org. Cort is the Trustee of the WA0EDA Club, and the chief engineer for K0USY Group; he is also known for his work as the author of the DMRlink, HBlink and dmr_utils software packages used by independent DMR networks around the globe.
This article is part one of a three part series on the STM32-DVM-MTR2K. Click here to read part two.