STM32-DVM-MTR2K v.2.0c

[LA4AMA]

Is there a original Linux MMDVM file to be downloaded and flashed to the micro SD-card on the MTR2K modem ?
The SD-card on my modem contains nothing.....



I did also try another micro SC-card with Pi-Star Nano-Pi Air v. 4.1.4 on it, but the Network card does not seem to function.
My DHCP router shows no connection to the MTR2K card, there is no activity on the network LED on the MTR2K card either.

EDIT 15:03 local time:
And then I found out what was wrong. I had to use the Nano-Pi file, not the nano-Pi Air.
Then it works fine.

http://www.pistar.uk/beta/Pi-Star_NanoP ... b-2021.zip

Ouuchhh....

LA4AMA
Roar

[LA4AMA]

The modem from Cort Buffington works great. I believe the MTR2K modem from Repeater-Builder is nearly identical.
Cort's modem comes with his own software, which is Linux-based, but I installed Pi-Star on my setup because I am lousy at using Linux.
Info:
http://ks-dmr.net/stm32-dvm-mtr2k-information/

Repeater-Builder:
http://www.repeater-builder.com/product ... MTR2k.html


I got help from Cort on how to setup the Motorola MTR-2000 repeater without using the WL (Wireline) card that came with most of these repeaters.
The Wireline card was installed in the upper position inside the MTR-2000:


I have written a complete setup of this installation in the attached PDF file:

https://www70.zippyshare.com/v/WPKCSlpX/file.html

The MTR-2000 from Motorola is a great repeater. I see quite a few of them on eBay etc.

I also installed a small 60x60mm fan behind the front panel that blows cool air directly onto the Nano-Pi:



I used double sided adhesive tape (Stokvis SuperTape VST4050C) and some strong glue to hold it in place.

There is a setting in Pi-Star (under Configuration and then click on EXPERT and MMDVMHost and go down to Modem) for using COS as Lockout for MMDVM, it should be set to 1:



ADDED 23 may 2021: Also note that sometimes the value TX Invert can be set to 1 as default, it should be set to 0 !!
(If it is set to 1 the repeater will just transmit a short burst in DMR mode).

The only issue I found was that the CW ID is not sendt with CTCSS on transmit, but that can be done if you are using an external FM repeater controller. I am looking into setting up a MTR-2000 with digital modem and external FM controller, the small and inexpensive ID-O-Matic IV. A great unit that I have been using a lot on Tait T-800 II and Tait TB-7100.

[LA4AMA]

One important addition to the above adjustments on the MTR-2000 is what I found out today:

I noticed that a second MTR-2000 I was adjusting did not functioned properly in DMR despite all the adjustments done in the PDF I made.

When I investigated further, I found that the transmitter was about 1 kHz too high in frequency. I did look at the transmit spectrum on the Anritsu MS2721B via a 60dB attenuator (transmitter at 5W).



I then did perform the Reference Oscillator (Manual) calibration in the Motorola RSS software, found under Station Alignment:



I had to increase the value a bout 7-8 "clicks" until it was dead on the correct carrier frequency. I used a very fine RBW on the Anritsu (10 Hz) and only 1 kHz span, to see the details and get better accuracy:



After this was done, the DMR now works flawless, so it seems the carrier frequency should be checked whenever these old MTR-2000 repeaters are used with the STM32-DVM_MTR2K digital modem.

Best of luck to yo all
LA4AMA
Roar
Norway

[LA4AMA]

Finally I did the last adjustments on the MTR-2000 with the borrowed Aeroflex 3920 with DMR option.

At first, I did get some odd FM deviation results, so I performed the TX deviation alignment under "Service" and "Station Alignment":



It takes you to a table with several frequencies that the repeater will transmit, and you should use your FM deviation analyzer (with only a 5kHz LPF) to measure what deviation you get on each frequency, and then input the value into each section.

After that is done, click on Save, and then click on Save in the Station Alignment window. The MTR-2000 reboots.

Leaving the DMR TX level at 50 % in Pi-Star, I did reach a reasonable level of performance in DMR mode, measured on the Aeroflex 3920:

Slot 1:



Slot 2:



In FM the result was very fine:



Best regards
LA4AMA
Roar
Norway

[kc0cap]

The modem from Cort Buffington works great. I believe the MTR2K modem from Repeater-Builder is nearly identical.
Cort's modem comes with his own software, which is Linux-based, but I installed Pi-Star on my setup because I am lousy at using Linux.
Info:
http://ks-dmr.net/stm32-dvm-mtr2k-information/

Repeater-Builder:
http://www.repeater-builder.com/product ... MTR2k.html


I got help from Cort on how to setup the Motorola MTR-2000 repeater without using the WL (Wireline) card that came with most of these repeaters.
The Wireline card was installed in the upper position inside the MTR-2000:


I have written a complete setup of this installation in the attached PDF file:

https://www70.zippyshare.com/v/WPKCSlpX/file.html

The MTR-2000 from Motorola is a great repeater. I see quite a few of them on eBay etc.

I also installed a small 60x60mm fan behind the front panel that blows cool air directly onto the Nano-Pi:



I used double sided adhesive tape (Stokvis SuperTape VST4050C) and some strong glue to hold it in place.

There is a setting in Pi-Star (under Configuration and then click on EXPERT and MMDVMHost and go down to Modem) for using COS as Lockout for MMDVM, it should be set to 1:



ADDED 23 may 2021: Also note that sometimes the value TX Invert can be set to 1 as default, it should be set to 0 !!
(If it is set to 1 the repeater will just transmit a short burst in DMR mode).

The only issue I found was that the CW ID is not sendt with CTCSS on transmit, but that can be done if you are using an external FM repeater controller. I am looking into setting up a MTR-2000 with digital modem and external FM controller, the small and inexpensive ID-O-Matic IV. A great unit that I have been using a lot on Tait T-800 II and Tait TB-7100.

HI, just curious how you wired the front cooling fan? Thanks