MMDVM Modems for MTR2000 & MASTR III

MTR2000 Version

KS-DMR and WA0EDA are not affiliated with Repeater Builder and do not support Repeater Builder products.

Purchasing a Modem

We created the original station-specific plug-in modems for the Motorola MTR2000 and GE/Harris MASTR III. Prices include USPS Priority mail in the US. International orders not accepted. Customers are strongly encouraged to view the manual prior to ordering to ensure they are comfortable installing and configuring the modem.

For more information, contact:
Cort Buffington, N0MJS

STM32-DVM-MTR2K: $185.00
For the MTR2000. Includes GPIO, wildcard, and serial port I/O communications.

Limited Availability – email to inquire.

STM32-DVM-MASTR3: $185.00
For GE/Harris MASTR III stations with EXT_HSD signal on the backplane.


Manuals, Articles & Tutorials


Much of the circuitry of the STM32-DVM-MTR2K and SMT32-DVM-MASTR3 is the same. Both use the same filters, the same modem processors, NanoPI NEO single board computer, etc. Most of the information contained here is applicable to both.


Articles & Tutorials:

Schematics and PCB Layouts



Firmware Updates

Binary Modem Firmware Files For Both Boards. Compiled on 25 May, 2020. Includes support for DMR, D-Star, YSF, P25, NXDN, POCSAG, FM.
(Instructions for updating are in the manual).

Compiled with COR used as a Modem inhibit (normal operation)

Compiled with COR used as a COR (might be useful for FM mode)

Binary Firmware Files for the STM32-DVM-MTR2K I/O Processor
(Instructions for updating are in the manual)

  • ATMEGA328P – 20200404 release with startup light show


The artwork is licensed under the Creative Commons BY-NC-SA 4.0 share-alike license. Which means you may do anything non-commercially you like with it, but you must provide attribution, even if you modify it. Which means you can pretty much do whatever you like, but you have to give credit to the Regents of the K0USY Group, and we prefer you just use the EDA logo.

Older Versions and File Archives