Bron: PD0ZRY
Through a fellow ham i got hold of 2 Motorola MTR2000 repeaters with the plan to convert them to DMR using the MMDVM board made by G4KLX. Here are my notes
Special thanks go out to Graziano IZ5IGB for building the first MMDVM MTR2000 and helping me get started.
Parts
- Motorola MTR2000 (no aditional cards are needed)
- RSS software (programming the repeater)
- Programming cable
- MMDVM board
- Arduino DUE
- Some device that runs linux
MTR2000
You can find my working codeplug here
Settings in the configuration file:
- TX 438.9875
- RX 431.3875
- Power 2 watt (minimal setting)
- Wireline board: TTN5067 4 wire (this board is not needed)
Step 1
Possibly it would be required to change some settings in the RSS to make it work with your repeater
Load the codeplug in the repeater
Step 2
Ajust the external audio input diviation
find the Service menu, then go to station Alignment
Under transmitter find Aux TX Input
Put the repeater in TX
Adjust input to maximum (255) and end transmission now save everything (the repeater will reboot)
Step 3
Wire the System connector
I have not tested wiring the RSSI output at this time due to the missing hardware (old version mmdvm board)
Step 4
Install and configure MMDVM and MMDVMHost (i will not cover this, there is plenty of info around)
Modem config in MMDVM.ini
[Modem]
Port=/dev/ttyACM0
TXInvert=1
RXInvert=1
PTTInvert=0
TXDelay=100
DMRDelay=162
RXLevel=50
TXLevel=50
# CWIdTXLevel=50
# D-StarTXLevel=50
# DMRTXLevel=50
# YSFTXLevel=50
# P25TXLevel=50
OscOffset=0
RSSIMultiplier=1
RSSIOffset=10
Debug=0
The main difference of the Modem block is in the DMRDelay this feature is there to compensate delay in the repeater of around 7 msec best setting should be somewhere between 162 and 168
IZ5IGB found that there is a phase shift of 2 signals createing about 7 msec delay.
Step 5
Adjust the MMDVM board untill the point you can tx/rx over the repeater i suggest starting with the tx side of the repeater. Depending on the MMDVM board this could take a while calibrating the pots on the mmdvm board took me about 30 min with just 1 dmr radio the repeater preforms well
