STM32-DVM-MTR2K v.2.0c

Help with other MMDVM Repeater Boards (with NO onboard RF)
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LA4AMA
Posts: 9
Joined: Fri Jun 05, 2020 1:00 pm

STM32-DVM-MTR2K v.2.0c

Post by 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.....

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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
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Last edited by LA4AMA on Tue May 25, 2021 7:08 pm, edited 2 times in total.
LA4AMA
Posts: 9
Joined: Fri Jun 05, 2020 1:00 pm

Re: STM32-DVM-MTR2K v.2.0c Repeater

Post by 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:
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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:

Image

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:

Image

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
Posts: 9
Joined: Fri Jun 05, 2020 1:00 pm

Re: STM32-DVM-MTR2K v.2.0c

Post by 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).

Image

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

Image

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:

Image

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
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Norway
KE7FNS
Pi-Star Team
Posts: 1805
Joined: Wed Apr 17, 2019 11:11 pm

Re: STM32-DVM-MTR2K v.2.0c

Post by KE7FNS »

Are you seriously still using Windows XP? :shock:
If someones previous actions are any indication of their future actions, then I predict the deletion and removal of access will happen at any moment. 7-11-2020.

"07/13/20 This Website Has Been Taken Down" ... again :lol:
LA4AMA
Posts: 9
Joined: Fri Jun 05, 2020 1:00 pm

Re: STM32-DVM-MTR2K v.2.0c

Post by LA4AMA »

Yes, Windows XP works fine with the Motorola RSS , Hi Hi.
(This is just an old computer used only for programming older stuff).

I finally got the chance to borrow an Aeroflex 3920 with DMR option.

Tested and fine-tuned DMR transmit from the repeater, it's now as close to the ideal parameters as I can get it.

Image

I found that FM deviation was quite a bit off, and performed the TX Deviation adjustment under Station Alignment:

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FM deviation is now OK, I got 2.9 kHz deviation out on TX with 3kHz deviation input from the signal generator. And with very low distortion (2.8 %).

One thing I noticed is that C4FM (Yaesu Fusion) test directly from the handheld into the Aeroflex FM analyzer shows 4.6 kHz deviation. But out from the MTR-2000 I can get a maximum of 3.8 kHz deviation even if YSF TX level is set to 100 % in Pi-star Modem setting (DMR TX level is at 50 %). It may be the deviation limiter in the MTR-2000 that restricts the full bandwidth.....
KE7FNS
Pi-Star Team
Posts: 1805
Joined: Wed Apr 17, 2019 11:11 pm

Re: STM32-DVM-MTR2K v.2.0c

Post by KE7FNS »

LA4AMA wrote: Sun Jun 06, 2021 9:31 am Yes, Windows XP works fine with the Motorola RSS , Hi Hi.
(This is just an old computer used only for programming older stuff).
Use a VM.
If someones previous actions are any indication of their future actions, then I predict the deletion and removal of access will happen at any moment. 7-11-2020.

"07/13/20 This Website Has Been Taken Down" ... again :lol:
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